suspicious of a bad calb cell?

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suspicious of a bad calb cell?

Electric Vehicle Discussion List mailing list
Hello, I recently upgraded my lead-acid EV conversion to lithium,
specifically 46 CALB 72Ah cells. I've been conservative in my bms settings,
not allowing any cell to go above 3.55V or below 2.6V (hopefully
"conservative" limits with calb-published limits of 3.65 and 2.5
respectively). I took care when I got the batteries to balance them; I've
also been careful to not charge when the temp is below 0C. I've been driving
with them for about a month now and have been really happy with the results
so far (especially after shedding over a kilopound of battery weight!) But
just this week I've become suspicious of one particular cell: now during
charging its voltage rises significantly faster than the other cells, and of
course once it reaches 3.55V, my charger pauses/ turns off, meaning the
other cells don't get as much charge as intended. Then all the cells find a
"resting voltage" nearly equal to each other (including the suspect cell).
But of course once charging resumes, the one cell still rises faster than
the rest.

Today I've had some luck turning down the current on the charger enough so
that the shunting in the BMS can (mostly) keep up, allowing the remaining
cells to charge. (Though this means of course that charging is taking much
longer.) Is this a sign I got a bad cell? I also have a PowerLab8 (that I
haven't used in a long time), so I may experiment with it when I get some
time later in the week... These cells should still be under warranty, so I
can explore that route, but thought I'd get some feedback here first;
thanks!

Philip Rash
http://www.evalbum.com/3381

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Re: suspicious of a bad calb cell?

Electric Vehicle Discussion List mailing list
Philip,

Another problem may be a bad connection between the cells, so that a
cell voltage is seen including the drop in the wire.
But yeah, you can have a bad cell as well, a quick way to check is to
watch what the BMS says during driving - does the bad cell
also drop quickly?
Another way to check if the BMS or the cell is a problem is to swap two
cells and re-connect the wires and BMS in the same way
so the cell is in a different spot according the BMS.
Success!
Cor.

-----Original Message-----
From: EV [mailto:[hidden email]] On Behalf Of rash via EV
Sent: Monday, February 05, 2018 7:21 PM
To: [hidden email]
Cc: rash
Subject: [EVDL] suspicious of a bad calb cell?

Hello, I recently upgraded my lead-acid EV conversion to lithium,
specifically 46 CALB 72Ah cells. I've been conservative in my bms
settings, not allowing any cell to go above 3.55V or below 2.6V
(hopefully "conservative" limits with calb-published limits of 3.65 and
2.5 respectively). I took care when I got the batteries to balance them;
I've also been careful to not charge when the temp is below 0C. I've
been driving with them for about a month now and have been really happy
with the results so far (especially after shedding over a kilopound of
battery weight!) But just this week I've become suspicious of one
particular cell: now during charging its voltage rises significantly
faster than the other cells, and of course once it reaches 3.55V, my
charger pauses/ turns off, meaning the other cells don't get as much
charge as intended. Then all the cells find a "resting voltage" nearly
equal to each other (including the suspect cell).
But of course once charging resumes, the one cell still rises faster
than the rest.

Today I've had some luck turning down the current on the charger enough
so that the shunting in the BMS can (mostly) keep up, allowing the
remaining cells to charge. (Though this means of course that charging is
taking much
longer.) Is this a sign I got a bad cell? I also have a PowerLab8 (that
I haven't used in a long time), so I may experiment with it when I get
some time later in the week... These cells should still be under
warranty, so I can explore that route, but thought I'd get some feedback
here first; thanks!

Philip Rash
http://www.evalbum.com/3381

--
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Re: suspicious of a bad calb cell?

Electric Vehicle Discussion List mailing list
I would individually test the suspect cell's actual amp-hour capacity, and
compare it with factory specs, AND also compare it witth with the actual
capacity of one or more other cells in your battery.  If it's substantially
lower than either, I'd say a warranty claim is justified.

Good luck!

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: suspicious of a bad calb cell?

Electric Vehicle Discussion List mailing list
In reply to this post by Electric Vehicle Discussion List mailing list
Did you lightly sand (or Scotchbite) each terminal and apply a thin
coating of NoAlOx before connecting? No? Then you have to redo all the
connections. They will give you no end of grief. (Ask me how I know. :-) )

If you don't do this connection treatment, the dissimilar metals will
corrode, over heat, and behave badly in general. Often, the cell
terminals arrive with a lot of corrosion formed during shipping.

Bill D.

On 2/5/2018 8:34 PM, Cor van de Water via EV wrote:

> Philip,
>
> Another problem may be a bad connection between the cells, so that a
> cell voltage is seen including the drop in the wire.
> But yeah, you can have a bad cell as well, a quick way to check is to
> watch what the BMS says during driving - does the bad cell
> also drop quickly?
> Another way to check if the BMS or the cell is a problem is to swap two
> cells and re-connect the wires and BMS in the same way
> so the cell is in a different spot according the BMS.
> Success!
> Cor.
>
> -----Original Message-----
> From: EV [mailto:[hidden email]] On Behalf Of rash via EV
> Sent: Monday, February 05, 2018 7:21 PM
> To: [hidden email]
> Cc: rash
> Subject: [EVDL] suspicious of a bad calb cell?
>
> Hello, I recently upgraded my lead-acid EV conversion to lithium,
> specifically 46 CALB 72Ah cells. I've been conservative in my bms
> settings, not allowing any cell to go above 3.55V or below 2.6V
> (hopefully "conservative" limits with calb-published limits of 3.65 and
> 2.5 respectively). I took care when I got the batteries to balance them;
> I've also been careful to not charge when the temp is below 0C. I've
> been driving with them for about a month now and have been really happy
> with the results so far (especially after shedding over a kilopound of
> battery weight!) But just this week I've become suspicious of one
> particular cell: now during charging its voltage rises significantly
> faster than the other cells, and of course once it reaches 3.55V, my
> charger pauses/ turns off, meaning the other cells don't get as much
> charge as intended. Then all the cells find a "resting voltage" nearly
> equal to each other (including the suspect cell).
> But of course once charging resumes, the one cell still rises faster
> than the rest.
>
> Today I've had some luck turning down the current on the charger enough
> so that the shunting in the BMS can (mostly) keep up, allowing the
> remaining cells to charge. (Though this means of course that charging is
> taking much
> longer.) Is this a sign I got a bad cell? I also have a PowerLab8 (that
> I haven't used in a long time), so I may experiment with it when I get
> some time later in the week... These cells should still be under
> warranty, so I can explore that route, but thought I'd get some feedback
> here first; thanks!
>
> Philip Rash
> http://www.evalbum.com/3381
>
> --
> Sent from: http://electric-vehicle-discussion-list.413529.n4.nabble.com/
> _______________________________________________
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> Please discuss EV drag racing at NEDRA
> (http://groups.yahoo.com/group/NEDRA)
>
> _______________________________________________
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>
>

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Re: suspicious of a bad calb cell?

Electric Vehicle Discussion List mailing list
Bill Dube via EV wrote:
> Did you lightly sand (or Scotchbite) each terminal and apply a thin
> coating of NoAlOx before connecting? No? Then you have to redo all the
> connections. They will give you no end of grief. (Ask me how I know. :-) )
>
> If you don't do this connection treatment, the dissimilar metals will
> corrode, over heat, and behave badly in general. Often, the cell
> terminals arrive with a lot of corrosion formed during shipping.

Bill has it right! I've had Thundersky, CALB, and GBS cells, and *all of
them have at least one aluminum terminal. It is devilishly difficult to
make reliable low-resistance connections to aluminum.

I've even wondered if there is some way to plate them with copper or
nickel; or spot-weld some easier-to-connect metal tab to the terminals.

--
It is vanity to do with more that which can be done with less.
         -- William of Ockham
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: suspicious of a bad calb cell?

Electric Vehicle Discussion List mailing list
In reply to this post by Electric Vehicle Discussion List mailing list
Thanks for the suggestions - I've definitely got some things to try - I'm
running a cycle on the suspect cell on the PowerLab8 tonight; will do a
"good" cell after that. I also need to redo the connections, as Bill
suggested. I'll report back in a while after I know more; thanks again!


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Re: suspicious of a bad calb cell?

Electric Vehicle Discussion List mailing list
In reply to this post by Electric Vehicle Discussion List mailing list
You are aware that 3.00V resting is considered dead right?

Also, the 3C current rating is very optimistic. Drawing 216A for more
than a few seconds is not good for life.

Even drawing 1C (72A) on a continuous basis will lead to a short life.

Since you are running a low voltage pack, I'm guessing you are drawing
relatively high current.

Low voltage packs should use at least 100Ah cells and preferably 180Ah
cells or higher.

Al


On 2/5/2018 10:20 PM, rash via EV wrote:
> Hello, I recently upgraded my lead-acid EV conversion to lithium,
> specifically 46 CALB 72Ah cells. I've been conservative in my bms settings,
> not allowing any cell to go above 3.55V or below 2.6V (hopefully
> "conservative" limits with calb-published limits of 3.65 and 2.5
>

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Re: suspicious of a bad calb cell?

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In reply to this post by Electric Vehicle Discussion List mailing list
Probably the best plating to use would be Alodine (AKA Bonderite). Not
terribly difficult to do. A bit pricey, but you would only have to coat
a tiny area.
Alodine is the conductive, gold/brown plating used on aluminum aircraft
parts. Great for corrosion prevention. Conducts very well (unlike
anodizing.)
Abrasively clean the aluminum surface, slightly etch with AlumiPrep,
rinse with distilled water, dip in Alondine, (or brush on,) rinse with
distilled water. You could do it yourself, actually. I have done it
myself with aircraft parts.
Unfortunately, Alodine is a chromate solution, which must be carefully
contained. (Erin Brokovich became famous for suing on behalf of chromate
pollution victims.)
As I understand it, they make non-chromate Alodine-like plating
solutions. Might be worth looking into.
You buy Bonderite from Aircraft Spruce:
http://www.aircraftspruce.com/categories/building_materials/bm/menus/cs/metalprepsupplies.html
https://en.wikipedia.org/wiki/Chromate_conversion_coating

Bill D.

On 2/6/2018 11:44 AM, Lee Hart via EV wrote:

> Bill Dube via EV wrote:
>> Did you lightly sand (or Scotchbite) each terminal and apply a thin
>> coating of NoAlOx before connecting? No? Then you have to redo all the
>> connections. They will give you no end of grief. (Ask me how I know.
>> :-) )
>>
>> If you don't do this connection treatment, the dissimilar metals will
>> corrode, over heat, and behave badly in general. Often, the cell
>> terminals arrive with a lot of corrosion formed during shipping.
>
> Bill has it right! I've had Thundersky, CALB, and GBS cells, and *all
> of them have at least one aluminum terminal. It is devilishly
> difficult to make reliable low-resistance connections to aluminum.
>
> I've even wondered if there is some way to plate them with copper or
> nickel; or spot-weld some easier-to-connect metal tab to the terminals.
>

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Re: suspicious of a bad calb cell?

Electric Vehicle Discussion List mailing list
Bill Dube via EV wrote:

> Probably the best plating to use would be Alodine (AKA Bonderite). Not
> terribly difficult to do. A bit pricey, but you would only have to coat
> a tiny area.
> Alodine is the conductive, gold/brown plating used on aluminum aircraft
> parts. Great for corrosion prevention. Conducts very well (unlike
> anodizing.)
> Abrasively clean the aluminum surface, slightly etch with AlumiPrep,
> rinse with distilled water, dip in Alondine, (or brush on,) rinse with
> distilled water. You could do it yourself, actually. I have done it
> myself with aircraft parts.
> Unfortunately, Alodine is a chromate solution, which must be carefully
> contained. (Erin Brokovich became famous for suing on behalf of chromate
> pollution victims.)
> As I understand it, they make non-chromate Alodine-like plating
> solutions. Might be worth looking into.
> You buy Bonderite from Aircraft Spruce:
> http://www.aircraftspruce.com/categories/building_materials/bm/menus/cs/metalprepsupplies.html
>
> https://en.wikipedia.org/wiki/Chromate_conversion_coating

Thanks, Bill! I've seen alodyne coatings, but never checked its
electrical conductivity. I'll dig around in my midden heap, and if I can
find an aluminum part with Alodyne, I'll try a connection and see what
kind of resistivity I get.

As it happens, I just got a set of used CALB cells to put in my LeCar,
so the timing is excellent. :-)

--
It is vanity to do with more that which can be done with less.
         -- William of Ockham
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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