Range dropping like a lead balloon: Pack Dying or ??

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Range dropping like a lead balloon: Pack Dying or ??

Danpatgal
This post was updated on .
I have 15 x 8v PbA flooded Interstate batteries in series on my Lectric Leopard (curb weight 2660 lbs) and have been noticing a bit of range reduction over the past few weeks.  My range had been 35-40 miles, but is now only about 20-25.  Here are changes in the past few months that I suspect as causes:

#1: New front tires (not LRR, but I have them at 42psi)
#2: Colder weather (average in the 30-40F for a high, but I do garage my car at night)
#3: Sagging pack / dead battery (Curtis fuel gague at 80% down, voltmeter read 60% SOC: most batts at 7.7v, one at 7.4v.  The pack has no more than 350 cycles on it, but is roughly a year and a half old.)
#4: Problem in transmission / drive train adding friction
#5: Charging with an Elcon at 240v instead of 120v

I realize these all have could have an effect (not sure why #5 would, but I don't know chargers that well), but is there a cause I should be investigating first?  My inclination is the pack, in particular the one battery at 7.4v, which would drag the others down.  

I realize I should be keeping my SOC higher (DOD lower), but with the range dropping kind of fast recently, I've not been able to adjust quickly enough.
 
Any thoughts - and remedies?  I hear I should take the low battery out and slowly charge to try and get it better.  (Though, when charging the pack and at lower DODs, I've checked the voltage and it doesn't read much lower than the others or the same when fully charged).

Going into winter I've wondered if I'd be so disappointed with lead acids that I'd dump the pack and spend the bigger bucks to go for lithium batteries ... but I'm not quite there yet (didn't get my tax refund yet ;) and I'm not sure it's just the colder weather.

Thanks - Dan


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Re: Range dropping like a lead balloon: Pack Dying or ??

Voltswagon
The cold is killer, that's when my pack started to tank.  Lead likes to be toasty, so even temps below 70 reduce your range, and 50 will make a big difference.

You'll drop extra fast because your effective range is reduced with the cold, but your commute is the same, so your DOD goes up lots which weakens the pack, and it goes into a death cycle where every time you're out your DOD will be higher.
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Re: Range dropping like a lead ballon: Pack Dying or ??

Cor van de Water
In reply to this post by Danpatgal
Dan,
The voltages on your batteries make no sense, unless
you are talking about under load.
When sitting idle, every cell should have more than 2V
or it is already empty. 8V batteries that read 7.7V
tells me that most likely your voltmeter is not reading
correct, or you are quoting from a certain load, so please
specify which load that the batts are under for 7.7V reading.

Another issue is if that one laggart was always lower or that
it started with the new charger?
Maybe you are under-charging, so the lower one never can catch
up as equalization is not happening? Just guessing here.

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
Skype: cor_van_de_water     XoIP: +31877841130
Tel: +1 408 383 7626        Tel: +91 (040)23117400 x203

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf Of Danpatgal
Sent: Thursday, February 09, 2012 12:14 PM
To: [hidden email]
Subject: [EVDL] Range dropping like a lead ballon: Pack Dying or ??

I have 15 x 8v PbA flooded Interstate batteries in series on my Lectric
Leopard (curb weight 2660 lbs) and have been noticing a bit of range
reduction over the past few weeks.  My range had been 35-40 miles, but
is now only about 20-25.  Here are changes in the past few months that I
suspect as causes:

#1: New front tires (not LRR, but I have them at 42psi)
#2: Colder weather (average in the 30-40F for a high, but I do garage my
car at night)
#3: Sagging pack / dead battery (Curtis fuel gague at 80% down,
voltmeter read 60% SOC: most batts at 7.7v, one at 7.4v.  The pack has
no more than 350 cycles on it, but is roughly a year and a half old.)
#4: Problem in transmission / drive train adding friction
#5: Charging with an Elcon at 240v instead of 120v

I realize these all have could have an effect (not sure why #5 would,
but I don't know chargers that well), but is there a cause I should be
investigating first?  My inclination is the pack, in particular the one
battery at 7.4v, which would drag the others down.  

I realize I should be keeping my SOC higher (DOD lower), but with the
range dropping kind of fast recently, I've not been able to adjust
quickly enough.
 
Any thoughts - and remedies?  I hear I should take the low battery out
and slowly charge to try and get it better.  (Though, when charging the
pack and at lower DODs, I've checked the voltage and it doesn't read
much lower than the others or the same when fully charged).

Going into winter I've wondered if I'd be so disappointed with lead
acids that I'd dump the pack and spend the bigger bucks to go for
lithium batteries ... but I'm not quite there yet (didn't get my tax
refund yet ;) and I'm not sure it's just the colder weather.

Thanks - Dan




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Dan Gallagher
http://www.evalbum.com/3854

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Re: Range dropping like a lead ballon: Pack Dying or ??

EVDL Administrator
In reply to this post by Danpatgal
On 9 Feb 2012 at 12:13, Danpatgal wrote:

> #1: New front tires (not LRR, but I have them at 42psi)

Maybe.  I'd suggest Inflating to the max pressure stated on the sidewall.

If your conversion still has stock fore/aft weight distribution (admittedly
unlikely), maintain the factory recommended front/rear differential at the
higher pressures.

Since most EVs don't run for hours on the highway, building up heat, you can
even run 10% over the sidewall max with very little risk.  

> #2: Colder weather (average in the 30-40F for a high, but I do garage
> my car at night)

This is the big one.  See if you can get a thermometer or temp probe down
into a few different cells and find out what the electrolyte temperature is.

> #3: Sagging pack / dead battery (Curtis fuel gague at 80% down, voltmeter
> read 60% SOC: most batts at 7.7v, one at 7.4v.  The pack has no more than
> 350 cycles on it, but is roughly a year and a half old.)

I'm assuming this is under load (acceleration?  cruise?) and they didn't sag
as much before.  Low temperature increases a battery's internal resistance,
so that again could be the culprit.  

The one outlier might be a bit weaker than the rest, or it might be colder.  

Where you have to really worry is when one battery is ~2v less than the
others - that usually means it has a bum cell.

> #4: Problem in transmission / drive train adding friction  

Another possible culprit.  Can you be more specific?

> #5: Charging with an Elcon at 240v instead of 120v

I doubt that this would have a negative effect, but I might be missing
something.

David Roden
EVDL Administrator
http://www.evdl.org/


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Re: Range dropping like a lead ballon: Pack Dying or ??

Danpatgal
In reply to this post by Cor van de Water
Thanks for the comments so far.  The 7.7v and 7.4v readings are back at home using my handheld multi-meter.  I don't have a PakTrakr, so I only check periodically - before these recent range drops I didn't read anything less than 8.0.  So, I was shocked to have read such low values the first time (and kicking myself for letting it go so low a second).  Today when I came home (it was sunnier, so the batts in the car [10 of the 15], were probably nice and warm) I got values more around 8.0v and 7.9 for my weak one.  In fact, as David mentioned, it is perhaps the "cold" one since it sits out front of the rest and more fully exposed.

I also suspect the Elcon doesn't do the gassing on 240v as it did on 120v ... not sure why that would be.  Just for a change I charged it yesterday at 120v, and got a bit more of the sulfur smell then I'd been getting recently with charging at 240 ... so it certainly could be that I was undercharging and/or not getting an equalization charge.

 
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Re: Range dropping like a lead ballon: Pack Dying or ??

Mark Grasser
I don't remember if you said they were flooded batteries. If they are
absorption charge voltage per battery should be 9.8 to 9.9 volts, a periodic
equalization voltage to blow off some sulfur would be 10.0 to 10.3 volts.

Resting voltage, which means after charging but no charger on and maybe a
drive around the block, a city block, to take off the surface charge, should
be 8.4 volts

Sincerely,
Mark Grasser
 


-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of Danpatgal
Sent: Thursday, February 09, 2012 6:57 PM
To: [hidden email]
Subject: Re: [EVDL] Range dropping like a lead ballon: Pack Dying or ??

Thanks for the comments so far.  The 7.7v and 7.4v readings are back at home
using my handheld multi-meter.  I don't have a PakTrakr, so I only check
periodically - before these recent range drops I didn't read anything less
than 8.0.  So, I was shocked to have read such low values the first time
(and kicking myself for letting it go so low a second).  Today when I came
home (it was sunnier, so the batts in the car [10 of the 15], were probably
nice and warm) I got values more around 8.0v and 7.9 for my weak one.  In
fact, as David mentioned, it is perhaps the "cold" one since it sits out
front of the rest and more fully exposed.

I also suspect the Elcon doesn't do the gassing on 240v as it did on 120v
... not sure why that would be.  Just for a change I charged it yesterday at
120v, and got a bit more of the sulfur smell then I'd been getting recently
with charging at 240 ... so it certainly could be that I was undercharging
and/or not getting an equalization charge.

 

-----
Dan Gallagher
http://www.evalbum.com/3854

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like-a-lead-balloon-Pack-Dying-or-tp4374229p4374866.html
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Re: Range dropping like a lead ballon: Pack Dying or ??

Roger Stockton
In reply to this post by Danpatgal
Danpatgal wrote:

> I also suspect the Elcon doesn't do the gassing on 240v as it did on 120v
> ... not sure why that would be.  Just for a change I charged it yesterday
> at 120v, and got a bit more of the sulfur smell then I'd been getting
> recently with charging at 240 ... so it certainly could be that I was
> undercharging and/or not getting an equalization charge.

When the battery is cold, it will have more internal resistance, and when you charge from 240VAC the charger delivers higher current to the battery.

The combination of higher resistance and higher current means that the battery voltage seen by the charger will be higher at a given state of charge (SOC) than when charging at lower current from 120VAC, or when the battery is warmer.  This could fool the charger into thinking the battery is more charged than that it really is, and result in the charger stopping before the battery is full.

If the charger isn't temperature-compensated, then it might undercharge the battery just because it is cold; if, or to what degree this happens depends on just how the charger decides when to stop charging.

Cheers,

Roger.
 

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Re: Range dropping like a lead ballon: Pack Dying or ??

EVDL Administrator
In reply to this post by Danpatgal
On 9 Feb 2012 at 15:56, Danpatgal wrote:

> Just for a change I charged it yesterday at 120v, and got a bit more of
> the sulfur smell then I'd been getting recently with charging at 240 ...

Gassing batteries will usually emit a notable tang from the acid vapor.  If
you're actually getting a sulfur odor, you're almost certainly overcharging,
and may be in danger of driving one or more batteries into thermal runaway.

David Roden
EVDL Administrator
http://www.evdl.org/


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Re: Range dropping like a lead ballon: Pack Dying or ??

Danpatgal
In reply to this post by Mark Grasser
Mark Grasser wrote
I don't remember if you said they were flooded batteries.
Yes they are flooded (I hate watering them).  I hope I'm not death spiraling them in the cold (I'm going to bicycle to work tomorrow).

Dan
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Re: Range dropping like a lead ballon: Pack Dying or ??

Danpatgal
In reply to this post by EVDL Administrator
EVDL Administrator wrote
Gassing batteries will usually emit a notable tang from the acid vapor.  If
you're actually getting a sulfur odor ...
I didn't quite know how to describe the smell - it wasn't really strong sulfur, maybe more the tang you're speaking of ...

Thanks - Dan.
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Re: Range dropping like a lead ballon: Pack Dying or ??

Mark Grasser
Then there is temp compensation. 0.028 volts per cell per 10degF is the
formula, I think. It starts at about 75degF. This equates to an extra 0.45
volts per battery at 35degF. This is battery temp though so be careful.
Roger could probably help here. He's one of those guys I talk about that's
smarter than me!


Sincerely,
Mark Grasser
 

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of Danpatgal
Sent: Thursday, February 09, 2012 8:35 PM
To: [hidden email]
Subject: Re: [EVDL] Range dropping like a lead ballon: Pack Dying or ??


EVDL Administrator wrote
>
> Gassing batteries will usually emit a notable tang from the acid vapor.
> If
> you're actually getting a sulfur odor ...

I didn't quite know how to describe the smell - it wasn't really strong
sulfur, maybe more the tang you're speaking of ...

Thanks - Dan.


-----
Dan Gallagher
http://www.evalbum.com/3854

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Re: Range dropping like a lead ballon: Pack Dying or ??

Roger Stockton
Mark Grasser wrote:

> Then there is temp compensation. 0.028 volts per cell per 10degF is the
> formula, I think. It starts at about 75degF. This equates to an extra 0.45
> volts per battery at 35degF. This is battery temp though so be careful.
> Roger could probably help here. He's one of those guys I talk about that's
> smarter than me!

If you're referring to this Roger, you didn't leave much for me to help with ;^>

As you say, it is battery temperature that matters, so the first question is probably does the charger have a sensor to measure the battery temperature, and if not, is one available for purchase as an optional accessory?

If there is one, or if one can be added, then the question is if the charger will automatically detect and use the sensor, or does the charger need to be reprogrammed or reconfigured in some way (move an internal jumper or switch)?

Roger.


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Re: Range dropping like a lead ballon: Pack Dying or ??

Danpatgal
Roger Stockton wrote
Mark Grasser wrote:

> Then there is temp compensation. 0.028 volts per cell per 10degF is the
> formula, I think. It starts at about 75degF. This equates to an extra 0.45
> volts per battery at 35degF. This is battery temp though so be careful.
> Roger could probably help here. He's one of those guys I talk about that's
> smarter than me!

If you're referring to this Roger, you didn't leave much for me to help with ;^>

As you say, it is battery temperature that matters, so the first question is probably does the charger have a sensor to measure the battery temperature, and if not, is one available for purchase as an optional accessory?

If there is one, or if one can be added, then the question is if the charger will automatically detect and use the sensor, or does the charger need to be reprogrammed or reconfigured in some way (move an internal jumper or switch)?

Roger.
Thanks Roger/Mark - that makes a lot of sense that charging at 240vac might undercharge as resistance and current go up.  There is a temperature probe on my Elcon, but maybe it ceased working or only "cares" about high temperatures, not low, the website states:

4. Intelligent temperature compensation function in the charging process, preventing damage to the battery caused by charge-off or charge due, greatly extending the lifespan of the battery.

7.The thermal compensation probe for the battery voltage must be placed in the area of the highest battery temperature, such as between 2 batteries near the center of the pack.


Since they mention putting the probe on the battery of highest temp (not lowest or average or something else), makes me suspect that it compensates only if it goes above a certain temperature, not if it goes below.  But I'll have to contact them and see what they say.

Thanks again for all the comments - it has really eased some of my stress about my range dropping!

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Re: Range dropping like a lead ballon: Pack Dying or ??

Roger Stockton
Danpatgal wrote:

> There is a temperature probe
> on my Elcon, but maybe it ceased working or only "cares" about high
> temperatures, not low, the website states:
>
> /4. Intelligent temperature compensation function in the charging process,
> preventing damage to the battery caused by charge-off or charge due,
> greatly
> extending the lifespan of the battery.
>
> 7.The thermal compensation probe for the battery voltage must be placed in
> the area of the highest battery temperature, such as between 2 batteries
> near the center of the pack./
>
> Since they mention putting the probe on the battery of *highest *temp (not
> lowest or average or something else), makes me suspect that it compensates
> only if it goes *above *a certain temperature, not if it goes below.  But
> I'll have to contact them and see what they say.

Most likely, the positioning recommendation is just based on the assumption that most often people will need the charger to protect the batteries from overcharge in warm/hot environments.

In your case, moving the sensor to the coldest location (e.g. an outward facing side of a battery that is on the outside of the pack.

This "do I measure the hottest or coldest point" issue is precisely why it is very desirable to install the pack in a single box, or to use thermal management to ensure that all cells are near to the same temperature.  The worst case is a fairly typical configuration of having some batteries under the hood in open racks and the rest in a box in the rear of the vehicle (especially when the vehicle happens to be a hatchback with a nice big window letting the sun beat down on the rear batteries ;^).

I would be very surprised if the charger did not use the battery temperature measurement to continuously adjust the charging voltage over the entire operating range.  It might additionally use the measurement to prevent charging above or below certain temperature limits, though this is less common.

Cheers,

Roger.


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