Keeping LiFePO4 battery terminals tight every 10k miles

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Keeping LiFePO4 battery terminals tight every 10k miles

Mark Hanson-2
Hi Folk's,
last night a overvoltage battery balancer #22 shut down the charger at 4.0V.  At first I thought it was a bad OV balancer detector but after replacing the circuit it still did it so I put a scope across the battery cell and noticed the charging pulsed waveform going from 3.3V to 4.0V 60 hz when adjacent cells were fairly solid (signifying a high impedance condition).  I thought I had a bad cell but after sanding under the copper strap & adding 3M dielectric grease & torquing back down, it charged perfectly with no faults, back to low impedance.  I found a few other battery terminal bolts not tight after 20k miles (even with sealing paint on terminal bolts CALB 130).  So it's best to tighten terminal bolts on lithiums every 10k miles it seams.  I used to tighten terminal bolts on old lead GC batteries every 500 miles but didn't think it was necessary with lithiums but apparently they need it as well just less often.
Best Regards,mark      
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Michael Ross
I recently took apart a nice little OEM battery pack and every terminal on
it was barely hand tight.  I reassembled with SS socket head screws instead
of the Phillips screws, and torqued the 5mm bolts to spec.  All you need to
do is torque them right and they will not loosen.  Do not use lock washers
as they compromise the clamping force. If you look at bolted joints on high
quality equipment you will find properly designed joints with no
lubrication or thread-locker - they just torque the right.  I worked for
Caterpillar and can vouch for their practices - needed to survive the worst
vibration environments imaginable.  My Toyota cars over the last 30 years
are all produced this way.  I don't use conductive grease, I just go with
clean and tight.

For reference:

1 N m = 8.8in lb = 0.74bft lb

I tightened the 5's to 35 in lb (4 Nm).

Unfortunately, there are a lot of units for measuring torque.   Inch pounds
are best for the small wrenches we have in the US.

My joints were the terminals of 32120 cells, SS M5 screws, with nickel
plated copper straps, and stainless steel flat washers (lock washers thrown
away).  I am not sure what the terminal with the tapped threads is made
from.  It is s tamped and formed part, maybe SS, but could be a plated
brass or copper...

On Mon, Jan 6, 2014 at 7:26 AM, Mark Hanson <[hidden email]>wrote:

> Hi Folk's,
> last night a overvoltage battery balancer #22 shut down the charger at
> 4.0V.  At first I thought it was a bad OV balancer detector but after
> replacing the circuit it still did it so I put a scope across the battery
> cell and noticed the charging pulsed waveform going from 3.3V to 4.0V 60 hz
> when adjacent cells were fairly solid (signifying a high impedance
> condition).  I thought I had a bad cell but after sanding under the copper
> strap & adding 3M dielectric grease & torquing back down, it charged
> perfectly with no faults, back to low impedance.  I found a few other
> battery terminal bolts not tight after 20k miles (even with sealing paint
> on terminal bolts CALB 130).  So it's best to tighten terminal bolts on
> lithiums every 10k miles it seams.  I used to tighten terminal bolts on old
> lead GC batteries every 500 miles but didn't think it was necessary with
> lithiums but apparently they need it as well just less often.
> Best Regards,mark
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>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Roland Wiench
In reply to this post by Mark Hanson-2
There is a battery link test that can be done to check the conductance of the link connection.  Connect a milliamp meter in the 0.001 amp range in parallel with the battery link.  Only connected to the battery post, not to the end of the link or the post connection.

Here we are testing the resistance of the link connection to the battery post as per A=E/R.  This test is done with the battery charger on adjusted to about 5 ampere.

When I do this test, I apply and wear electrical safety equipment, which includes electrical gloves, a electrical rubber blanket or a neoprene 1/8 inch rubber mat that covers all the battery connections except the one that is being tested.

Also cover any metal on the car and use a rubber floor mat to stand on.  

It is also important to torque the battery connection to the specifications for that type of connection.  These normally run from 50 to 100 in.lbs. (inch pounds).  I used a standard in.lb. torque wrench that I will initially adjust and then slip over a electrical rating neoprene rubber tube over the handle.

In initially installing battery links for the first time, I will use a standard insulated ratchet and socket to tighten the nut to where you think is good.  I have train electrical technicians to do this initial tightening and many thought the torque would be at least 50 inch lbs. It was not!  Testing out the torque with a torque wrench show the torque valve to be 10 to 15 in.lbs under specifications.

After you do the initial hand tightening, connected the amp meter adjusted to 0.001 amp and turn on the battery charger to 5 amps.  You will see that the ampere reading may be between 0.1 to 0.001 amps.  Tighten the links fasteners to the specific torque level which may read 0.08 amps.  You than torque all the other links to the same valve.  

After a load is apply to the battery, it is common for the battery line resistance to increase.  It is recommend after the first 5 mile drive, is to check the torque level again.  My batteries which is a standard auto post type, will lose about 5 in.lbs.  Re-torque again and the loss may be 1 to 2 in.lbs in about a week.  In about a month, the torque value will be in about 1 in.lbs.  I now only check the torque value every six months when I water and clean the batteries.

Roland    

   
  ----- Original Message -----
  From: Mark Hanson<mailto:[hidden email]>
  To: [hidden email]<mailto:[hidden email]>
  Sent: Monday, January 06, 2014 5:26 AM
  Subject: [EVDL] Keeping LiFePO4 battery terminals tight every 10k miles


  Hi Folk's,
  last night a overvoltage battery balancer #22 shut down the charger at 4.0V.  At first I thought it was a bad OV balancer detector but after replacing the circuit it still did it so I put a scope across the battery cell and noticed the charging pulsed waveform going from 3.3V to 4.0V 60 hz when adjacent cells were fairly solid (signifying a high impedance condition).  I thought I had a bad cell but after sanding under the copper strap & adding 3M dielectric grease & torquing back down, it charged perfectly with no faults, back to low impedance.  I found a few other battery terminal bolts not tight after 20k miles (even with sealing paint on terminal bolts CALB 130).  So it's best to tighten terminal bolts on lithiums every 10k miles it seams.  I used to tighten terminal bolts on old lead GC batteries every 500 miles but didn't think it was necessary with lithiums but apparently they need it as well just less often.
  Best Regards,mark      
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Bill Dube
In reply to this post by Michael Ross
You have to sand the terminals and immediately apply NoAlOx, just like
Mark says. A thin layer is best as a thick layer will slowly ooze out
and the terminal will become loose.

Re torquing is needed, but probably not every 10k miles. Likely just the
first 5k to 10k and then maybe at 30k or 40k.

Bellville washers help.
http://en.wikipedia.org/wiki/Belleville_washer

Bill D.

On 1/6/2014 7:22 AM, Michael Ross wrote:

> I recently took apart a nice little OEM battery pack and every terminal on
> it was barely hand tight.  I reassembled with SS socket head screws instead
> of the Phillips screws, and torqued the 5mm bolts to spec.  All you need to
> do is torque them right and they will not loosen.  Do not use lock washers
> as they compromise the clamping force. If you look at bolted joints on high
> quality equipment you will find properly designed joints with no
> lubrication or thread-locker - they just torque the right.  I worked for
> Caterpillar and can vouch for their practices - needed to survive the worst
> vibration environments imaginable.  My Toyota cars over the last 30 years
> are all produced this way.  I don't use conductive grease, I just go with
> clean and tight.
>
> For reference:
>
> 1 N m = 8.8in lb = 0.74bft lb
>
> I tightened the 5's to 35 in lb (4 Nm).
>
> Unfortunately, there are a lot of units for measuring torque.   Inch pounds
> are best for the small wrenches we have in the US.
>
> My joints were the terminals of 32120 cells, SS M5 screws, with nickel
> plated copper straps, and stainless steel flat washers (lock washers thrown
> away).  I am not sure what the terminal with the tapped threads is made
> from.  It is s tamped and formed part, maybe SS, but could be a plated
> brass or copper...
>
> On Mon, Jan 6, 2014 at 7:26 AM, Mark Hanson <[hidden email]>wrote:
>
>> Hi Folk's,
>> last night a overvoltage battery balancer #22 shut down the charger at
>> 4.0V.  At first I thought it was a bad OV balancer detector but after
>> replacing the circuit it still did it so I put a scope across the battery
>> cell and noticed the charging pulsed waveform going from 3.3V to 4.0V 60 hz
>> when adjacent cells were fairly solid (signifying a high impedance
>> condition).  I thought I had a bad cell but after sanding under the copper
>> strap & adding 3M dielectric grease & torquing back down, it charged
>> perfectly with no faults, back to low impedance.  I found a few other
>> battery terminal bolts not tight after 20k miles (even with sealing paint
>> on terminal bolts CALB 130).  So it's best to tighten terminal bolts on
>> lithiums every 10k miles it seams.  I used to tighten terminal bolts on old
>> lead GC batteries every 500 miles but didn't think it was necessary with
>> lithiums but apparently they need it as well just less often.
>> Best Regards,mark
>> -------------- next part --------------
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>> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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>> For EV drag racing discussion, please use NEDRA (
>> http://groups.yahoo.com/group/NEDRA)
>>
>>
>

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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Michael Ross
Hi Bill,

From my own experience with non-electrical bolted joints, re-torquing is
not ever necessary, given the torque is right to start with, the parts fit
right, are of the proper grade, and clean.

The only reason for the forces to drop is if there is a compliant material
in the joint that takes a compression set. Compression set due to thermal
cycling is about the only way to lose clamping force. There might be a way
if there are foreign materials present.  I am not saying you are wrong, but
I do want to know why it has happened.

Do you have any ideas?  What mechanism is allowing the components of the
joint to compress enough allowing the screw to back out?


The whole idea of proper joint design and selection of clamping force(the
torque applied) is to ensure that under all operating and storage
conditions, including thermal cycling, that sufficient clamping is always
remaining and no loosening can occur.

I am very skeptical.  Also the torque to release a joint gives no
indication of the applied torque or the remaining clamping force.  You
simply cannot reliably measure that.


NoALOx is only useful for aluminum according to product literature, the
joint I discussed has only copper and stainless in it. The theory of this
stuff has an appeal - is there any evidence?  I have a hard time believing
in aluminum surfaces that are not oxidized (except in a vacuum).

I would like hear what people know about the electrical properties of
clamped joints.  I don't know much about that.  I do know a bit about
switch contacts, but the forces are much smaller (and yet they function
somehow, with no gook in between).  I am from Missouri on this topic.

I apologize to all, I have probably raised two religious topics.  But I
have not been around the block on these in this context.



On Mon, Jan 6, 2014 at 10:49 AM, Bill Dube <[hidden email]> wrote:

> You have to sand the terminals and immediately apply NoAlOx, just like
> Mark says. A thin layer is best as a thick layer will slowly ooze out and
> the terminal will become loose.
>
> Re torquing is needed, but probably not every 10k miles. Likely just the
> first 5k to 10k and then maybe at 30k or 40k.
>
> Bellville washers help.
> http://en.wikipedia.org/wiki/Belleville_washer
>
> Bill D.
>
> On 1/6/2014 7:22 AM, Michael Ross wrote:
>
>> I recently took apart a nice little OEM battery pack and every terminal on
>> it was barely hand tight.  I reassembled with SS socket head screws
>> instead
>> of the Phillips screws, and torqued the 5mm bolts to spec.  All you need
>> to
>> do is torque them right and they will not loosen.  Do not use lock washers
>> as they compromise the clamping force. If you look at bolted joints on
>> high
>> quality equipment you will find properly designed joints with no
>> lubrication or thread-locker - they just torque the right.  I worked for
>> Caterpillar and can vouch for their practices - needed to survive the
>> worst
>> vibration environments imaginable.  My Toyota cars over the last 30 years
>> are all produced this way.  I don't use conductive grease, I just go with
>> clean and tight.
>>
>> For reference:
>>
>> 1 N m = 8.8in lb = 0.74bft lb
>>
>> I tightened the 5's to 35 in lb (4 Nm).
>>
>> Unfortunately, there are a lot of units for measuring torque.   Inch
>> pounds
>> are best for the small wrenches we have in the US.
>>
>> My joints were the terminals of 32120 cells, SS M5 screws, with nickel
>> plated copper straps, and stainless steel flat washers (lock washers
>> thrown
>> away).  I am not sure what the terminal with the tapped threads is made
>> from.  It is s tamped and formed part, maybe SS, but could be a plated
>> brass or copper...
>>
>> On Mon, Jan 6, 2014 at 7:26 AM, Mark Hanson <[hidden email]>
>> wrote:
>>
>>  Hi Folk's,
>>> last night a overvoltage battery balancer #22 shut down the charger at
>>> 4.0V.  At first I thought it was a bad OV balancer detector but after
>>> replacing the circuit it still did it so I put a scope across the battery
>>> cell and noticed the charging pulsed waveform going from 3.3V to 4.0V 60
>>> hz
>>> when adjacent cells were fairly solid (signifying a high impedance
>>> condition).  I thought I had a bad cell but after sanding under the
>>> copper
>>> strap & adding 3M dielectric grease & torquing back down, it charged
>>> perfectly with no faults, back to low impedance.  I found a few other
>>> battery terminal bolts not tight after 20k miles (even with sealing paint
>>> on terminal bolts CALB 130).  So it's best to tighten terminal bolts on
>>> lithiums every 10k miles it seams.  I used to tighten terminal bolts on
>>> old
>>> lead GC batteries every 500 miles but didn't think it was necessary with
>>> lithiums but apparently they need it as well just less often.
>>> Best Regards,mark
>>> -------------- next part --------------
>>> An HTML attachment was scrubbed...SNIP
>>
>>
--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Lee Hart
In reply to this post by Mark Hanson-2
Mark Hanson wrote:
> ... I found a few other battery terminal bolts not tight after 20k
> miles (even with sealing paint on terminal bolts CALB 130).
> So it's best to tighten terminal bolts on lithiums every 10k miles it
> seems. I used to tighten terminal bolts on old lead GC batteries
> every 500 miles but didn't think it was necessary with lithiums but
> apparently they need it as well just less often.

Soft metals like lead, aluminum, and copper can "cold flow" due to
pressure. Temperature cycling and vibration also play a part.

Unfortunately, these factors are common in electrical connections. These
soft metals are used for their high electrical conductivity. High
currents make the temperature extremes worse due to self-heating.

Dis-similar metals are another factor. These create corrosion couples,
that corrode if the joint isn't absolutely air tight. They expand at
different rates with temperature, leading to large pressure changes in
the joint. Inexperienced or cheapskate designers seem to have a total
disregard for the metals used in their electrical contacts. They ignore
100 years of experience and use whatever metals are handy.

My guess is that if (for example) you bolt a copper strip to an aluminum
stud with a stainless steel screw, it's hopeless to expect a reliable
connection.
--
"Obsolete" means nothing more than "the salesmen would prefer you buy
something else." -- Dave McGuire
--
Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Michael Ross
Lee,

Those metals are elastic up to a point, and all behave according to Young's
Modulus.  If you don't exceed the yield strength, then they DO NOT
experience permanent deformation.

There is no lead involved with the large and small format Li cells that I
have seen and the aluminum and copper will not cold flow unless the bolts
are tightened too much, the bulk metal won't compress then, but the threads
will strip.

Regarding lead, it also behaves by Young's Modulus, but has a very low
yield strength.  If you don't exceed the yield strength it will be as good
as steel.  However the clamping force may be too low.  Temperature does not
significantly effect elasticity of metals, as long as you don't melt them.
 You do have account for differences in thermal expansion when the joint
has huge changes in temperature. Then you need a higher torque.

Bottom line - use the right fasteners, clean surfaces, no rubber or plastic
washers, torque them correctly, and there will be no loss of clamping force.



I agree copper directly onto aluminum is a bad choice.  Proper plating is
how to get by.  You don't get a galvanic couple when you plate.  For
example good chrome on steel is a three layer process steel, polished, is
plated with copper to provide a barrier and good surface for adhesion of
the nickel layer and then chrome on top.

Corrosion couples require moisture.  If you put them together dry you can
get away with a lot, but dry is really hard to maintain, with overnight
changes of 30F degrees in humid conditions you get condensation.

The other factor is large differences in electronegativity (galvanic
potential) of the jointed touching metals.  If they are far apart in
galvanic potential you have more trouble.  Copper and zinc, copper and
nickel, copper and tin not so bad.  Copper and aluminum sucks. SS in
aluminum is not too bad.  I expect no problems from that.  Aluminum is kind
an odd beast because it is not really what we see on the surface but
instead the oxide of aluminum.

Here is a chart:
http://www.roymech.co.uk/Useful_Tables/Corrosion/Cor_bi_met.html
I like the format but the info is hazy. Is brass a copper or zinc alloy?


Here it is for all elements sorted by electronegativity:
http://www.lenntech.com/periodic-chart-elements/electronegativity.htm

Anyway a flat, tight, dry joint will stay that way and not corrode.

I can see where a grease would come in handy to keep moisture away.

I don't think this has much to do with torquing however.



On Mon, Jan 6, 2014 at 1:35 PM, Lee Hart <[hidden email]> wrote:

> Mark Hanson wrote:
>
>> ... I found a few other battery terminal bolts not tight after 20k
>>
>> miles (even with sealing paint on terminal bolts CALB 130).
>> So it's best to tighten terminal bolts on lithiums every 10k miles it
>> seems. I used to tighten terminal bolts on old lead GC batteries
>>
>> every 500 miles but didn't think it was necessary with lithiums but
>> apparently they need it as well just less often.
>>
>
> Soft metals like lead, aluminum, and copper can "cold flow" due to
> pressure. Temperature cycling and vibration also play a part.
>
> Unfortunately, these factors are common in electrical connections. These
> soft metals are used for their high electrical conductivity. High currents
> make the temperature extremes worse due to self-heating.
>
> Dis-similar metals are another factor. These create corrosion couples,
> that corrode if the joint isn't absolutely air tight. They expand at
> different rates with temperature, leading to large pressure changes in the
> joint. Inexperienced or cheapskate designers seem to have a total disregard
> for the metals used in their electrical contacts. They ignore 100 years of
> experience and use whatever metals are handy.
>
> My guess is that if (for example) you bolt a copper strip to an aluminum
> stud with a stainless steel screw, it's hopeless to expect a reliable
> connection.
> --
> "Obsolete" means nothing more than "the salesmen would prefer you buy
> something else." -- Dave McGuire
> --
> Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/
> group/NEDRA)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Roland Wiench
In reply to this post by Mark Hanson-2
In all electrical connections we use in devices such as wire terminals, buss bars, circuit breakers, circuit breaker buss connections, are cadmium plated copper or aluminum metals.  We do not use any contact aids on cadmium plated devices.

There is a shunt tester that can be purchase from electrical supply houses to test the conductance of a connection.  In some installations, we are required to record the data of the connections and verify by a QC inspector.

Roland  
  ----- Original Message -----
  From: Lee Hart<mailto:[hidden email]>
  To: Electric Vehicle Discussion List<mailto:[hidden email]>
  Sent: Monday, January 06, 2014 11:35 AM
  Subject: Re: [EVDL] Keeping LiFePO4 battery terminals tight every 10k miles


  Mark Hanson wrote:
  > ... I found a few other battery terminal bolts not tight after 20k
  > miles (even with sealing paint on terminal bolts CALB 130).
  > So it's best to tighten terminal bolts on lithiums every 10k miles it
  > seems. I used to tighten terminal bolts on old lead GC batteries
  > every 500 miles but didn't think it was necessary with lithiums but
  > apparently they need it as well just less often.

  Soft metals like lead, aluminum, and copper can "cold flow" due to
  pressure. Temperature cycling and vibration also play a part.

  Unfortunately, these factors are common in electrical connections. These
  soft metals are used for their high electrical conductivity. High
  currents make the temperature extremes worse due to self-heating.

  Dis-similar metals are another factor. These create corrosion couples,
  that corrode if the joint isn't absolutely air tight. They expand at
  different rates with temperature, leading to large pressure changes in
  the joint. Inexperienced or cheapskate designers seem to have a total
  disregard for the metals used in their electrical contacts. They ignore
  100 years of experience and use whatever metals are handy.

  My guess is that if (for example) you bolt a copper strip to an aluminum
  stud with a stainless steel screw, it's hopeless to expect a reliable
  connection.
  --
  "Obsolete" means nothing more than "the salesmen would prefer you buy
  something else." -- Dave McGuire
  --
  Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm<http://www.sunrise-ev.com/projects.htm>
  _______________________________________________
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

David Nelson-5
My Brass bolts, bronze lock washers with copper straps on my TS cells
have not come loose. I have 4 years on this pack now. I put NO-AL-OX
in the threads after cleaning the surface of the terminals and,
obviously, before putting the bolts in. If I ever have to redo my pack
I will clean off the gunky NO-AL-OX and use NO-OX-ID "A SPECIAL" since
it doesn't appear to get gunky.

Another method which has worked well for many is to use Nord-Lock
(www.nord-lock.com) washers instead of lock washers.

On Mon, Jan 6, 2014 at 1:09 PM, Roland <[hidden email]> wrote:

> In all electrical connections we use in devices such as wire terminals, buss bars, circuit breakers, circuit breaker buss connections, are cadmium plated copper or aluminum metals.  We do not use any contact aids on cadmium plated devices.
>
> There is a shunt tester that can be purchase from electrical supply houses to test the conductance of a connection.  In some installations, we are required to record the data of the connections and verify by a QC inspector.
>
> Roland
>   ----- Original Message -----
>   From: Lee Hart<mailto:[hidden email]>
>   To: Electric Vehicle Discussion List<mailto:[hidden email]>
>   Sent: Monday, January 06, 2014 11:35 AM
>   Subject: Re: [EVDL] Keeping LiFePO4 battery terminals tight every 10k miles
>
>
>   Mark Hanson wrote:
>   > ... I found a few other battery terminal bolts not tight after 20k
>   > miles (even with sealing paint on terminal bolts CALB 130).
>   > So it's best to tighten terminal bolts on lithiums every 10k miles it
>   > seems. I used to tighten terminal bolts on old lead GC batteries
>   > every 500 miles but didn't think it was necessary with lithiums but
>   > apparently they need it as well just less often.
>
>   Soft metals like lead, aluminum, and copper can "cold flow" due to
>   pressure. Temperature cycling and vibration also play a part.
>
>   Unfortunately, these factors are common in electrical connections. These
>   soft metals are used for their high electrical conductivity. High
>   currents make the temperature extremes worse due to self-heating.
>
>   Dis-similar metals are another factor. These create corrosion couples,
>   that corrode if the joint isn't absolutely air tight. They expand at
>   different rates with temperature, leading to large pressure changes in
>   the joint. Inexperienced or cheapskate designers seem to have a total
>   disregard for the metals used in their electrical contacts. They ignore
>   100 years of experience and use whatever metals are handy.
>
>   My guess is that if (for example) you bolt a copper strip to an aluminum
>   stud with a stainless steel screw, it's hopeless to expect a reliable
>   connection.
>   --
>   "Obsolete" means nothing more than "the salesmen would prefer you buy
>   something else." -- Dave McGuire
>   --
>   Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm<http://www.sunrise-ev.com/projects.htm>
>   _______________________________________________
>   UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub<http://www.evdl.org/help/index.html#usub>
>   http://lists.evdl.org/listinfo.cgi/ev-evdl.org<http://lists.evdl.org/listinfo.cgi/ev-evdl.org>
>   For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA<http://groups.yahoo.com/group/NEDRA>)
>
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--
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http://evalbum.com/1328
http://www.levforum.com
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Martin WINLOW
In reply to this post by Michael Ross
I'm slightly concerned that without qualification, inexperienced DIY EVrs will start over-torquing there connections.  Obviously, different size bots will require different torques.  When I bought my Thundersky cells in 2008, I could not get a sensible answer out of them about what torque to use for the bots (8mm in that case).  Anyone care to offer a rule of thumb for the usual 6mm and 8mm bolts used with most LiFePo4 cells?  MW



On 6 Jan 2014, at 14:22, Michael Ross wrote:

> I recently took apart a nice little OEM battery pack and every terminal on
> it was barely hand tight.  I reassembled with SS socket head screws instead
> of the Phillips screws, and torqued the 5mm bolts to spec.  All you need to
> do is torque them right and they will not loosen.  Do not use lock washers
> as they compromise the clamping force. If you look at bolted joints on high
> quality equipment you will find properly designed joints with no
> lubrication or thread-locker - they just torque the right.  I worked for
> Caterpillar and can vouch for their practices - needed to survive the worst
> vibration environments imaginable.  My Toyota cars over the last 30 years
> are all produced this way.  I don't use conductive grease, I just go with
> clean and tight.
>
> For reference:
>
> 1 N m = 8.8in lb = 0.74bft lb
>
> I tightened the 5's to 35 in lb (4 Nm).
>
> Unfortunately, there are a lot of units for measuring torque.   Inch pounds
> are best for the small wrenches we have in the US.
>
> My joints were the terminals of 32120 cells, SS M5 screws, with nickel
> plated copper straps, and stainless steel flat washers (lock washers thrown
> away).  I am not sure what the terminal with the tapped threads is made
> from.  It is s tamped and formed part, maybe SS, but could be a plated
> brass or copper...
>
> On Mon, Jan 6, 2014 at 7:26 AM, Mark Hanson <[hidden email]>wrote:
>
>> Hi Folk's,
>> last night a overvoltage battery balancer #22 shut down the charger at
>> 4.0V.  At first I thought it was a bad OV balancer detector but after
>> replacing the circuit it still did it so I put a scope across the battery
>> cell and noticed the charging pulsed waveform going from 3.3V to 4.0V 60 hz
>> when adjacent cells were fairly solid (signifying a high impedance
>> condition).  I thought I had a bad cell but after sanding under the copper
>> strap & adding 3M dielectric grease & torquing back down, it charged
>> perfectly with no faults, back to low impedance.  I found a few other
>> battery terminal bolts not tight after 20k miles (even with sealing paint
>> on terminal bolts CALB 130).  So it's best to tighten terminal bolts on
>> lithiums every 10k miles it seams.  I used to tighten terminal bolts on old
>> lead GC batteries every 500 miles but didn't think it was necessary with
>> lithiums but apparently they need it as well just less often.
>> Best Regards,mark

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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Martin WINLOW
In reply to this post by Michael Ross
And I forgot to mention the extra danger of rotating the terminal posts on LiFePO4 cells when using too much torque.  The last time I tried to torque my cell bolts to a recommended setting (I can't remember whose) the posts were rotating before I got near the recommended torque.  Obviously, rotating the terminals is NOT GOOD!
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Michael Ross
In reply to this post by Martin WINLOW
Martin,

It is necessary to have a properly sized torque wrench, the willingness to
look up the proper torque setting for the materials involved, and a
willingness to spend the time getting all of the bolts right.  The
alternative is you take a chance on shortening the life of an expensive
pack, or running out of power in transit.  It is a choice one makes not
torquing well.

Lot's of people think torquing is trivial.   That would not be true of OEM
auto manufacturers.  If one does not take their lead... If people don't
obtain the tool, look the torque up, and do it right, then they will either
under or over torque (I am shrugging, but not unsympathetic).  I can't
really worry about all the people who strip out threads - I did a fair
amount of that myself before deciding to do it right.

If a DIY EVr does strip some out we can help them retap or helicoil the
holes.  It does happen.

Here is a reference

http://bit.ly/1dsHSCw

Mike



On Tue, Jan 7, 2014 at 5:01 AM, Martin WINLOW <[hidden email]> wrote:

> I'm slightly concerned that without qualification, inexperienced DIY EVrs
> will start over-torquing there connections.  Obviously, different size bots
> will require different torques.  When I bought my Thundersky cells in 2008,
> I could not get a sensible answer out of them about what torque to use for
> the bots (8mm in that case).  Anyone care to offer a rule of thumb for the
> usual 6mm and 8mm bolts used with most LiFePo4 cells?  MW
>
>
>
> On 6 Jan 2014, at 14:22, Michael Ross wrote:
>
> > I recently took apart a nice little OEM battery pack and every terminal
> on
> > it was barely hand tight.  I reassembled with SS socket head screws
> instead
> > of the Phillips screws, and torqued the 5mm bolts to spec.  All you need
> to
> > do is torque them right and they will not loosen.  Do not use lock
> washers
> > as they compromise the clamping force. If you look at bolted joints on
> high
> > quality equipment you will find properly designed joints with no
> > lubrication or thread-locker - they just torque the right.  I worked for
> > Caterpillar and can vouch for their practices - needed to survive the
> worst
> > vibration environments imaginable.  My Toyota cars over the last 30 years
> > are all produced this way.  I don't use conductive grease, I just go with
> > clean and tight.
> >
> > For reference:
> >
> > 1 N m = 8.8in lb = 0.74bft lb
> >
> > I tightened the 5's to 35 in lb (4 Nm).
> >
> > Unfortunately, there are a lot of units for measuring torque.   Inch
> pounds
> > are best for the small wrenches we have in the US.
> >
> > My joints were the terminals of 32120 cells, SS M5 screws, with nickel
> > plated copper straps, and stainless steel flat washers (lock washers
> thrown
> > away).  I am not sure what the terminal with the tapped threads is made
> > from.  It is s tamped and formed part, maybe SS, but could be a plated
> > brass or copper...
> >
> > On Mon, Jan 6, 2014 at 7:26 AM, Mark Hanson <[hidden email]
> >wrote:
> >
> >> Hi Folk's,
> >> last night a overvoltage battery balancer #22 shut down the charger at
> >> 4.0V.  At first I thought it was a bad OV balancer detector but after
> >> replacing the circuit it still did it so I put a scope across the
> battery
> >> cell and noticed the charging pulsed waveform going from 3.3V to 4.0V
> 60 hz
> >> when adjacent cells were fairly solid (signifying a high impedance
> >> condition).  I thought I had a bad cell but after sanding under the
> copper
> >> strap & adding 3M dielectric grease & torquing back down, it charged
> >> perfectly with no faults, back to low impedance.  I found a few other
> >> battery terminal bolts not tight after 20k miles (even with sealing
> paint
> >> on terminal bolts CALB 130).  So it's best to tighten terminal bolts on
> >> lithiums every 10k miles it seams.  I used to tighten terminal bolts on
> old
> >> lead GC batteries every 500 miles but didn't think it was necessary with
> >> lithiums but apparently they need it as well just less often.
> >> Best Regards,mark
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
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> http://groups.yahoo.com/group/NEDRA)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

tomw
In reply to this post by Mark Hanson-2
I have 4 years and over 30k miles on my pack and have similar experience to David N.  I used noalox on the aluminum terminals like David, very thin coating right after sanding with fine emery and wiping them clean.  I have minibms module terminals over the lugs, then flat washer and lock washer - the hardware that came with the cells.  I used 10 - 12 ft-lb torque on the M8 bolts.  I have checked the terminals about every 6 to 12 months with a torque wrench.  The only time I found a loose connection was when I replaced a cell and forgot to fully tighten the nut, which I first detected with a bit larger than normal pack voltage sag, then with a cell log8 showing large voltage sag on that cell. I was stunned when I found I had not even finger tightened the nut!  Otherwise, none have required tightening.  They don't budge when I apply 10-12 ft-lb.  It is possible that the nut wasn't fully tightened originally - maybe snugged with a wrench, then missed the final torque.

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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Michael Ross
Tom,

You can loosen and re-torque, but you can't measure loss of torque. Some
joints will slip and give, some will give up quick, some may grab, and they
may have both been torqued the same.

If you follow good joint design, fastener selection, and torque to specs -
a joint will not loosen.
For an "unknown design" I would not suggest using the higher grad bolt
specs.  You don't know the class of fit/engagement so you would risk
stripping the tapped holes,  And aluminum is fiddly.  Better to assume 50%
engagement.  That should work just fine.


On Tue, Jan 7, 2014 at 9:59 AM, tomw <[hidden email]> wrote:

> I have 4 years and over 30k miles on my pack and have similar experience to
> David N.  I used noalox on the aluminum terminals like David, very thin
> coating right after sanding with fine emery and wiping them clean.  I have
> minibms module terminals over the lugs, then flat washer and lock washer -
> the hardware that came with the cells.  I used 10 - 12 ft-lb torque on the
> M8 bolts.  I have checked the terminals about every 6 to 12 months with a
> torque wrench.  The only time I found a loose connection was when I
> replaced
> a cell and forgot to fully tighten the nut, which I first detected with a
> bit larger than normal pack voltage sag, then with a cell log8 showing
> large
> voltage sag on that cell. I was stunned when I found I had not even finger
> tightened the nut!  Otherwise, none have required tightening.  They don't
> budge when I apply 10-12 ft-lb.  It is possible that the nut wasn't fully
> tightened originally - maybe snugged with a wrench, then missed the final
> torque.
>
>
>
>
>
> --
> View this message in context:
> http://electric-vehicle-discussion-list.413529.n4.nabble.com/Keeping-LiFePO4-battery-terminals-tight-every-10k-miles-tp4667172p4667221.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
> _______________________________________________
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> http://groups.yahoo.com/group/NEDRA)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
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(919) 513-0418 Desk

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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Evan Tuer
In reply to this post by Bill Dube
Oops, I've not done this once in 50k miles!  I used the Calb-supplied
hardware, which was stainless hex bolts, stainless washers and what looked
like spring steel lock washers.  Can't get NoAlOx here so didn't use it..




On Mon, Jan 6, 2014 at 3:49 PM, Bill Dube <[hidden email]> wrote:

> You have to sand the terminals and immediately apply NoAlOx, just like
> Mark says. A thin layer is best as a thick layer will slowly ooze out and
> the terminal will become loose.
>
> Re torquing is needed, but probably not every 10k miles. Likely just the
> first 5k to 10k and then maybe at 30k or 40k.
>
> Bellville washers help.
> http://en.wikipedia.org/wiki/Belleville_washer
>
> Bill D.
>
>
> On 1/6/2014 7:22 AM, Michael Ross wrote:
>
>> I recently took apart a nice little OEM battery pack and every terminal on
>> it was barely hand tight.  I reassembled with SS socket head screws
>> instead
>> of the Phillips screws, and torqued the 5mm bolts to spec.  All you need
>> to
>> do is torque them right and they will not loosen.  Do not use lock washers
>> as they compromise the clamping force. If you look at bolted joints on
>> high
>> quality equipment you will find properly designed joints with no
>> lubrication or thread-locker - they just torque the right.  I worked for
>> Caterpillar and can vouch for their practices - needed to survive the
>> worst
>> vibration environments imaginable.  My Toyota cars over the last 30 years
>> are all produced this way.  I don't use conductive grease, I just go with
>> clean and tight.
>>
>> For reference:
>>
>> 1 N m = 8.8in lb = 0.74bft lb
>>
>> I tightened the 5's to 35 in lb (4 Nm).
>>
>> Unfortunately, there are a lot of units for measuring torque.   Inch
>> pounds
>> are best for the small wrenches we have in the US.
>>
>> My joints were the terminals of 32120 cells, SS M5 screws, with nickel
>> plated copper straps, and stainless steel flat washers (lock washers
>> thrown
>> away).  I am not sure what the terminal with the tapped threads is made
>> from.  It is s tamped and formed part, maybe SS, but could be a plated
>> brass or copper...
>>
>> On Mon, Jan 6, 2014 at 7:26 AM, Mark Hanson <[hidden email]>
>> wrote:
>>
>>  Hi Folk's,
>>> last night a overvoltage battery balancer #22 shut down the charger at
>>> 4.0V.  At first I thought it was a bad OV balancer detector but after
>>> replacing the circuit it still did it so I put a scope across the battery
>>> cell and noticed the charging pulsed waveform going from 3.3V to 4.0V 60
>>> hz
>>> when adjacent cells were fairly solid (signifying a high impedance
>>> condition).  I thought I had a bad cell but after sanding under the
>>> copper
>>> strap & adding 3M dielectric grease & torquing back down, it charged
>>> perfectly with no faults, back to low impedance.  I found a few other
>>> battery terminal bolts not tight after 20k miles (even with sealing paint
>>> on terminal bolts CALB 130).  So it's best to tighten terminal bolts on
>>> lithiums every 10k miles it seams.  I used to tighten terminal bolts on
>>> old
>>> lead GC batteries every 500 miles but didn't think it was necessary with
>>> lithiums but apparently they need it as well just less often.
>>> Best Regards,mark
>>> -------------- next part --------------
>>> An HTML attachment was scrubbed...
>>> URL: <
>>> http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/
>>> 20140106/46bb23a0/attachment.htm
>>> _______________________________________________
>>> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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>>> For EV drag racing discussion, please use NEDRA (
>>> http://groups.yahoo.com/group/NEDRA)
>>>
>>>
>>>
>>
> _______________________________________________
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Michael Ross
Honestly, I think NoAlOX is Slick 50 all over again until I see some data.
 I would love to see data.

When you torque properly into aluminum you are getting airtight contact
with the pure aluminum of the threads by the sliding nature of the contact.
 It might be interesting to see how much resistance is really there across
the joint of the strap to the terminal.  My guess is it is really low as
there is a lot of area.  I am not convinced that sanding is useful -
especially if it is not dead flat  when you get done.  The contact is only
between asperities of the two surfaces no matter what you do and all that
finish work is unlikely to help.  You do not expose and un-oxidized
aluminum as it instantly reoxidizes when air touches it.  I do mean
instantly.  it is a fools errand and the machined surface if it is
undamaged is better.

I say throw away the lock washers, keep the flat ones and torque them to
spec with what you have.  If the threads are dry when you put it together
there will be no trouble.  You can smear some grease around if you want a
small measure of extra moisture resistance.  If you have to put something
on the threads and between the flat surfaces of contacts conductive grease
should be fine.  If NoAlOx is your preference then go for it. I would
probably go with a high conductivity heat transfer paste (not dielectric).
  But, I think clean and dry is best.


On Tue, Jan 7, 2014 at 12:10 PM, Evan Tuer <[hidden email]> wrote:

> Oops, I've not done this once in 50k miles!  I used the Calb-supplied
> hardware, which was stainless hex bolts, stainless washers and what looked
> like spring steel lock washers.  Can't get NoAlOx here so didn't use it..
>
>
>
>
> On Mon, Jan 6, 2014 at 3:49 PM, Bill Dube <[hidden email]> wrote:
>
> > You have to sand the terminals and immediately apply NoAlOx, just like
> > Mark says. A thin layer is best as a thick layer will slowly ooze out and
> > the terminal will become loose.
> >
> > Re torquing is needed, but probably not every 10k miles. Likely just the
> > first 5k to 10k and then maybe at 30k or 40k.
> >
> > Bellville washers help.
> > http://en.wikipedia.org/wiki/Belleville_washer
> >
> > Bill D.
> >
> >
> > On 1/6/2014 7:22 AM, Michael Ross wrote:
> >
> >> I recently took apart a nice little OEM battery pack and every terminal
> on
> >> it was barely hand tight.  I reassembled with SS socket head screws
> >> instead
> >> of the Phillips screws, and torqued the 5mm bolts to spec.  All you need
> >> to
> >> do is torque them right and they will not loosen.  Do not use lock
> washers
> >> as they compromise the clamping force. If you look at bolted joints on
> >> high
> >> quality equipment you will find properly designed joints with no
> >> lubrication or thread-locker - they just torque the right.  I worked for
> >> Caterpillar and can vouch for their practices - needed to survive the
> >> worst
> >> vibration environments imaginable.  My Toyota cars over the last 30
> years
> >> are all produced this way.  I don't use conductive grease, I just go
> with
> >> clean and tight.
> >>
> >> For reference:
> >>
> >> 1 N m = 8.8in lb = 0.74bft lb
> >>
> >> I tightened the 5's to 35 in lb (4 Nm).
> >>
> >> Unfortunately, there are a lot of units for measuring torque.   Inch
> >> pounds
> >> are best for the small wrenches we have in the US.
> >>
> >> My joints were the terminals of 32120 cells, SS M5 screws, with nickel
> >> plated copper straps, and stainless steel flat washers (lock washers
> >> thrown
> >> away).  I am not sure what the terminal with the tapped threads is made
> >> from.  It is s tamped and formed part, maybe SS, but could be a plated
> >> brass or copper...
> >>
> >> On Mon, Jan 6, 2014 at 7:26 AM, Mark Hanson <[hidden email]>
> >> wrote:
> >>
> >>  Hi Folk's,
> >>> last night a overvoltage battery balancer #22 shut down the charger at
> >>> 4.0V.  At first I thought it was a bad OV balancer detector but after
> >>> replacing the circuit it still did it so I put a scope across the
> battery
> >>> cell and noticed the charging pulsed waveform going from 3.3V to 4.0V
> 60
> >>> hz
> >>> when adjacent cells were fairly solid (signifying a high impedance
> >>> condition).  I thought I had a bad cell but after sanding under the
> >>> copper
> >>> strap & adding 3M dielectric grease & torquing back down, it charged
> >>> perfectly with no faults, back to low impedance.  I found a few other
> >>> battery terminal bolts not tight after 20k miles (even with sealing
> paint
> >>> on terminal bolts CALB 130).  So it's best to tighten terminal bolts on
> >>> lithiums every 10k miles it seams.  I used to tighten terminal bolts on
> >>> old
> >>> lead GC batteries every 500 miles but didn't think it was necessary
> with
> >>> lithiums but apparently they need it as well just less often.
> >>> Best Regards,mark
> >>> -------------- next part --------------
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> >>> http://groups.yahoo.com/group/NEDRA)
> >>>
> >>>
> >>>
> >>
> > _______________________________________________
> > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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> > group/NEDRA)
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>


--
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happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Lee Hart
In reply to this post by Michael Ross
Michael Ross wrote:
> It is necessary to have a properly sized torque wrench, the willingness to
> look up the proper torque setting for the materials involved, and a
> willingness to spend the time getting all of the bolts right.  The
> alternative is you take a chance on shortening the life of an expensive
> pack, or running out of power in transit.  It is a choice one makes not
> torquing well... http://bit.ly/1dsHSCw

Good advice, Michael. Thanks for the reference! (That's a new way to
look it up.)

It should be noted that sometimes the manufacturer's choice of materials
and recommended torque is woefully ignorant. For example, a stainless
steel screw in aluminum is a bad design choice. It's likely to be
electrically bad, and is also likely to gall and seize in time.

--
"Obsolete" means nothing more than "the salesmen would prefer you buy
something else." -- Dave McGuire
--
Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Jukka Järvinen-3
Well.. The whole pole assembly (in these certain prismatic cells) has been
under doubt for a decade now. Some failures but not as much as one would
think.

Many of you know the foils inside the cell are compressed together and
drilled with one or two holes. There are similar holes in the Al or Cu pole
assembly. Foils are tightened with stainless steel bolt and nut against the
pole blocks. Some washers included. And this is inside the cell where they
may be soaked in electrolyte. If the connection gets loose it will fail. On
some I've found just black goo where the bolt was supposed to be.

The idea is that the current goes where it most easiest go. Through tight
copper-copper or Al-Al connection. That steel bolt has no chance of
transferring any significant amount of current.

I would keep all lubricants and pastes away from the cell poles. As long as
they are dry they will work nicely for a decade. Clean and dry makes it
easier to find the loose connections. At every service I test drive the
vehicles and after some driving I measure every pole bolt manually for
heat. If the heating occurs (more than others) on any bolt that is already
tight it indicates internal bolt failure. Cell has to be changed.

Early indication is higher voltage drop with high discharge current but the
capacity seems to be there. BMS detects this failure easily.

As the depth of threads and length of bolts are not exact I tighten the
bolts manually 'tight enough'. After few thousand poles and bolts it's in
the wrist. The big problem is on cells that have been unbolted for a dozen
times. The Al pole looses it's threads. It happens when unbolting. Al
sticks to the stainless steel threads and we have nice hole on the pole
with no threads left. Depending on the case I change the whole cell or just
drill a bit bigger hole and rethread it for a bit larger bolt.

Spring washers and lockable bolts will keep the connection perfect at any
condition.

-Jukka

2014/1/7 Lee Hart <[hidden email]>

> Michael Ross wrote:
>
>> It is necessary to have a properly sized torque wrench, the willingness to
>> look up the proper torque setting for the materials involved, and a
>> willingness to spend the time getting all of the bolts right.  The
>> alternative is you take a chance on shortening the life of an expensive
>> pack, or running out of power in transit.  It is a choice one makes not
>> torquing well... http://bit.ly/1dsHSCw
>>
>
> Good advice, Michael. Thanks for the reference! (That's a new way to look
> it up.)
>
> It should be noted that sometimes the manufacturer's choice of materials
> and recommended torque is woefully ignorant. For example, a stainless steel
> screw in aluminum is a bad design choice. It's likely to be electrically
> bad, and is also likely to gall and seize in time.
>
> --
> "Obsolete" means nothing more than "the salesmen would prefer you buy
> something else." -- Dave McGuire
> --
> Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/
> group/NEDRA)
>
>
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Cor van de Water
Jukka,
The process that you describe for the AL threads sticking to the Stainless steel bolt is called "galling" AKA cold-welding. It can be reduced by lightly lubricating the threads, since it is not the threads that carry the current (the top surface of the terminal where the copper strap is bolted down onto is the current carrying surface, the stainless steel bolt is too high resistance and its only function is to hold the copper tightly clamped to the Alu terminal surface, so lubricating the threads will not alter the electrical behavior but reduce the galling.

NOTE that I have also seen corrosoin on Alu terminals where the case apparently was not completely tight and this or the neighbor cell leaked electrolyte, eating into the smooth Alu surface.
That is my reason to apply cheap Petroleum Jelly to all surfaces that are supposed to make good electrical contact or under mechanical stress, so the corroding fluids can't reach it and they stay clean. Any electrical contact is *not* affected by the grease, because even mild pressure will squeeze it out from between mating surfaces and the electrical connection is made clean and tight.
I have now also used it on my lead-acid terminals, since the brass clamps were eaten away by any leaked acid, forming beautiful (and poisonous) blue "flowers".
Keep your terminals clean & tight!

BTW, the earlier recommendation to look up the recommended torque force of steel bolts might be *very* misleading, because even for small 1/4" bolts the torque is at least 10 Ft-pound. That will very likely destroy your Alu terminal in short order, you need to use torque force for *Alu* if you are torqueing something into an Alu post.
Add the effect of galling which increases with higher force and temp and you are in for disaster if you over-torque your bolts. If the surfaces are clean then it takes wery little force and you probably are best off using strong split washers and applying only as little force as to take the split washer down until it is flat, no more and you are good. That is not much torque at all, but I have measured the resistance of even finger-tightened nuts and there is no difference with heavy torqueing, so keeping them clean is more important in my humble opinion and experience.

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email] Private: http://www.cvandewater.info
Skype: cor_van_de_water Tel: +1 408 383 7626

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Jukka Järvinen
Sent: Tuesday, January 07, 2014 3:02 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Keeping LiFePO4 battery terminals tight every 10k miles

Well.. The whole pole assembly (in these certain prismatic cells) has been
under doubt for a decade now. Some failures but not as much as one would
think.

Many of you know the foils inside the cell are compressed together and
drilled with one or two holes. There are similar holes in the Al or Cu pole
assembly. Foils are tightened with stainless steel bolt and nut against the
pole blocks. Some washers included. And this is inside the cell where they
may be soaked in electrolyte. If the connection gets loose it will fail. On
some I've found just black goo where the bolt was supposed to be.

The idea is that the current goes where it most easiest go. Through tight
copper-copper or Al-Al connection. That steel bolt has no chance of
transferring any significant amount of current.

I would keep all lubricants and pastes away from the cell poles. As long as
they are dry they will work nicely for a decade. Clean and dry makes it
easier to find the loose connections. At every service I test drive the
vehicles and after some driving I measure every pole bolt manually for
heat. If the heating occurs (more than others) on any bolt that is already
tight it indicates internal bolt failure. Cell has to be changed.

Early indication is higher voltage drop with high discharge current but the
capacity seems to be there. BMS detects this failure easily.

As the depth of threads and length of bolts are not exact I tighten the
bolts manually 'tight enough'. After few thousand poles and bolts it's in
the wrist. The big problem is on cells that have been unbolted for a dozen
times. The Al pole looses it's threads. It happens when unbolting. Al
sticks to the stainless steel threads and we have nice hole on the pole
with no threads left. Depending on the case I change the whole cell or just
drill a bit bigger hole and rethread it for a bit larger bolt.

Spring washers and lockable bolts will keep the connection perfect at any
condition.

-Jukka

2014/1/7 Lee Hart <[hidden email]>

> Michael Ross wrote:
>
>> It is necessary to have a properly sized torque wrench, the willingness to
>> look up the proper torque setting for the materials involved, and a
>> willingness to spend the time getting all of the bolts right.  The
>> alternative is you take a chance on shortening the life of an expensive
>> pack, or running out of power in transit.  It is a choice one makes not
>> torquing well... http://bit.ly/1dsHSCw
>>
>
> Good advice, Michael. Thanks for the reference! (That's a new way to look
> it up.)
>
> It should be noted that sometimes the manufacturer's choice of materials
> and recommended torque is woefully ignorant. For example, a stainless steel
> screw in aluminum is a bad design choice. It's likely to be electrically
> bad, and is also likely to gall and seize in time.
>
> --
> "Obsolete" means nothing more than "the salesmen would prefer you buy
> something else." -- Dave McGuire
> --
> Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/
> group/NEDRA)
>
>
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Re: Keeping LiFePO4 battery terminals tight every 10k miles

Michael Ross
In reply to this post by Jukka Järvinen-3
Hi Jukka,

Is that "tight enough" ± a smidge?  I am going with the torque wrench.

I watched a class once where people tried to control applied torque by feel
with the max hold set, but hidden, then check the max after to see how well
that worked.  It was just terrible.  A person might get it right once, but
they were unable to do very well repeatedly.

Then a set of seemingly identical joints were torqued, and the un-torquing
checked.  Again, no correlation to the applied torque.

I don't really doubt that you are able to do this and have no trouble -
this doesn't look like a very demanding application to me.  But some people
think that these joints will loosen over time.

My contention is this loosening is not because the joints are prone to
loosening, but that they were not torqued correctly to begin with, and
maybe sometimes not enough.  If you torque them right, they won't loosen -
ever.

Mike


On Tue, Jan 7, 2014 at 6:01 PM, Jukka Järvinen <[hidden email]>wrote:

> Well.. The whole pole assembly (in these certain prismatic cells) has been
> under doubt for a decade now. Some failures but not as much as one would
> think.
>
> Many of you know the foils inside the cell are compressed together and
> drilled with one or two holes. There are similar holes in the Al or Cu pole
> assembly. Foils are tightened with stainless steel bolt and nut against the
> pole blocks. Some washers included. And this is inside the cell where they
> may be soaked in electrolyte. If the connection gets loose it will fail. On
> some I've found just black goo where the bolt was supposed to be.
>
> The idea is that the current goes where it most easiest go. Through tight
> copper-copper or Al-Al connection. That steel bolt has no chance of
> transferring any significant amount of current.
>
> I would keep all lubricants and pastes away from the cell poles. As long as
> they are dry they will work nicely for a decade. Clean and dry makes it
> easier to find the loose connections. At every service I test drive the
> vehicles and after some driving I measure every pole bolt manually for
> heat. If the heating occurs (more than others) on any bolt that is already
> tight it indicates internal bolt failure. Cell has to be changed.
>
> Early indication is higher voltage drop with high discharge current but the
> capacity seems to be there. BMS detects this failure easily.
>
> As the depth of threads and length of bolts are not exact I tighten the
> bolts manually 'tight enough'. After few thousand poles and bolts it's in
> the wrist. The big problem is on cells that have been unbolted for a dozen
> times. The Al pole looses it's threads. It happens when unbolting. Al
> sticks to the stainless steel threads and we have nice hole on the pole
> with no threads left. Depending on the case I change the whole cell or just
> drill a bit bigger hole and rethread it for a bit larger bolt.
>
> Spring washers and lockable bolts will keep the connection perfect at any
> condition.
>
> -Jukka
>
> 2014/1/7 Lee Hart <[hidden email]>
>
> > Michael Ross wrote:
> >
> >> It is necessary to have a properly sized torque wrench, the willingness
> to
> >> look up the proper torque setting for the materials involved, and a
> >> willingness to spend the time getting all of the bolts right.  The
> >> alternative is you take a chance on shortening the life of an expensive
> >> pack, or running out of power in transit.  It is a choice one makes not
> >> torquing well... http://bit.ly/1dsHSCw
> >>
> >
> > Good advice, Michael. Thanks for the reference! (That's a new way to look
> > it up.)
> >
> > It should be noted that sometimes the manufacturer's choice of materials
> > and recommended torque is woefully ignorant. For example, a stainless
> steel
> > screw in aluminum is a bad design choice. It's likely to be electrically
> > bad, and is also likely to gall and seize in time.
> >
> > --
> > "Obsolete" means nothing more than "the salesmen would prefer you buy
> > something else." -- Dave McGuire
> > --
> > Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm
> > _______________________________________________
> > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> > http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> > For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/
> > group/NEDRA)
> >
> >
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>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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