# [EVDL] Possible Yellow Top Damage



## EVDL List (Jul 27, 2007)

I completed reverse capacity testing my 12 D31 Yellow Tops today, by
measuring the time to discharge down to 10.6V using a load of 60A.
Results overall were not too good:

49,51,45,41,19,41,40,37,20,47,45. 

Two clear duds, and all the others less than the 60 minutes (i.e. 60AH @
60A load) that I had thought the D31's were capable of. However perhaps
they will improve with age/commissioning charge etc.

So I took them back to the battery company I bought them from so they
could test them properly. By feeling across the top of each battery
they noticed some slight bulging across the top of each cell, and
suggested my charger may have damaged them. They showed me a brand new
D31 on their shelf - and sure enough - no bulging when I felt along the
top. The bulging is very slight - not visible by eye, but you can feel
it, a slight rise along the top of each cell. I don't know if these
bumps were present when I purchased the batteries.

They are going to carefully test each battery (and check my charger)
over the next few days which is nice of them.

Now in the 9 months since I bought them in November, these batteries
were charged twice using a Projecta 121045 smart charger. Then just
before the load tests I topped them up with a Powertech MB3612
dual-stage charger. I just checked both chargers and I never saw the
voltage exceed 14.1V (for example just before bulk charge to float
transition). Float is around 13.5V. So I suspect they might be
undercharging but not sure about damage from over-charging. No sign of
extended 15V periods for example.

The load tests for each D31 were 30 sec @ 200A, a recharge, then a
discharge down to 10.6V @ 60A. That's all these batteries have been
used for so far.

One other possibility is that while in storage they experienced a rather
hot summer, e.g. up to 45C/110F.

So I have a couple of questions:

1/ Are these slight bulges a sign of damage? 

2/ Am I naive to expect 60AH @ 60A out of these batteries, or is 40-50AH
@ 60A reasonable? The Peukert numbers using the D31 data (C=75AH at
C/20 discharge, and a capacity of 155 minutes at 25AH) suggests 60AH
however I am not sure if the Peukert model is a real world model.

Thank you very much for you help,

David

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## EVDL List (Jul 27, 2007)

The electrochemist I know that use to work for Optima (he doesn't want me to mention his name, because he doesn't have time to answer a lot of questions from the public) said that the bulging I saw (much more dramatic than "slight") on my used/abused yellowtops were an indication that they got overheated at some time, and softened up the plastic. I'm sure that some of mine did get very hot, but I can't imagine that 45C/110F is "too hot"; it's gotta get hotter than that under the hood of an ICE car.

It sounds like you have a very helpful battery dealer that's willing to talk with you and take you seriously.

Steven Ciciora

<snip>
> 
> One other possibility is that while in storage they
> experienced a rather
> hot summer, e.g. up to 45C/110F.
> 
<snip>




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## EVDL List (Jul 27, 2007)

> David Rowe wrote:
> > I completed reverse capacity testing my 12 D31 Yellow Tops today, by
> > measuring the time to discharge down to 10.6V using a load of 60A.
> > Results overall were not too good:
> ...


----------



## EVDL List (Jul 27, 2007)

Hello David,

The ampere draw out will not match the ampere-hour rating of the battery 
unless you test it at the 20 AH rating.

For example, a battery rated for 100 ampere-hour can deliver 5 amperes for 
20 hours (5 amperes x 20 hours = 100 amp-hrs)

Actual battery capacity decreases as discharge current increase. A battery 
rated at 100-hours which can deliver 5 amperes for 20 hours, may deliver 20 
amperes for only 4 hours, resulting in an actual capacity of 80 
ampere-hours.

To determine the battery capacity, calculate the actual ampere-hour by using 
the reserve capacity minutes that are listed for that battery. Lets say the 
reserve capacity of a 100 AH battery at 25 amps is 180 minutes and at 75 
amps is 40 minutes, then at:

25 amp load -

180 min / 60 = 3 hrs

3 hrs x 25 amps = 75 amp-hrs

75 amp load -

40 min / 60 = 0.66 hrs

0.66 hrs x 75 amps = 49.6 amp-hrs


As the ampere goes above the 20 hour rating of 5 amps for 100 AH, this 
battery will decrease in capacity as the ampere goes up. You have to input 
the reserve capacity for this battery as listed and see what the actual 
battery capacity is.

The above data is from my DC-AC power inverter manual by Statpower.

At a 60 amp load on a 75 AH battery the reserved capacity may between 30 and 
40 minutes.

To determine the size of a new replacement pack for my EV, I knew that I can 
run at 30 mph at 50 battery amperes at 150 motor amps on smooth level grade, 
or 75 battery amperes at 200 motor amps on rough grades.

I wanted at least a range of 60 minutes at the 75 battery ampere rate with a 
battery DOD or 50%, then I need a battery at 60 min x 2 = 120 minutes 
reserved at 75 amperes.

Looking at the battery chart, the closes one is a T-125 rated at 235 
ampere-hour and 132 reserved minutes at 75 amperes. So I now can draw 75 
amps for one hour and still have 50 percent capacity.

Roland





----- Original Message ----- 
From: "David Rowe" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Tuesday, August 05, 2008 3:25 AM
Subject: [EVDL] Possible Yellow Top Damage


> I completed reverse capacity testing my 12 D31 Yellow Tops today, by
> measuring the time to discharge down to 10.6V using a load of 60A.
> Results overall were not too good:
>
> 49,51,45,41,19,41,40,37,20,47,45.
>
> Two clear duds, and all the others less than the 60 minutes (i.e. 60AH @
> 60A load) that I had thought the D31's were capable of. However perhaps
> they will improve with age/commissioning charge etc.
>
> So I took them back to the battery company I bought them from so they
> could test them properly. By feeling across the top of each battery
> they noticed some slight bulging across the top of each cell, and
> suggested my charger may have damaged them. They showed me a brand new
> D31 on their shelf - and sure enough - no bulging when I felt along the
> top. The bulging is very slight - not visible by eye, but you can feel
> it, a slight rise along the top of each cell. I don't know if these
> bumps were present when I purchased the batteries.
>
> They are going to carefully test each battery (and check my charger)
> over the next few days which is nice of them.
>
> Now in the 9 months since I bought them in November, these batteries
> were charged twice using a Projecta 121045 smart charger. Then just
> before the load tests I topped them up with a Powertech MB3612
> dual-stage charger. I just checked both chargers and I never saw the
> voltage exceed 14.1V (for example just before bulk charge to float
> transition). Float is around 13.5V. So I suspect they might be
> undercharging but not sure about damage from over-charging. No sign of
> extended 15V periods for example.
>
> The load tests for each D31 were 30 sec @ 200A, a recharge, then a
> discharge down to 10.6V @ 60A. That's all these batteries have been
> used for so far.
>
> One other possibility is that while in storage they experienced a rather
> hot summer, e.g. up to 45C/110F.
>
> So I have a couple of questions:
>
> 1/ Are these slight bulges a sign of damage?
>
> 2/ Am I naive to expect 60AH @ 60A out of these batteries, or is 40-50AH
> @ 60A reasonable? The Peukert numbers using the D31 data (C=75AH at
> C/20 discharge, and a capacity of 155 minutes at 25AH) suggests 60AH
> however I am not sure if the Peukert model is a real world model.
>
> Thank you very much for you help,
>
> David
>
> _______________________________________________
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> Usage guidelines: http://evdl.org/help/index.html#conv
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>
> 

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## EVDL List (Jul 27, 2007)

Hi Roland,

Thank you for those examples. I used the D31 data to try and determine
the Peukert model for the battery:

1/ C=75AH at a discharge rate of C/20 = 75/20 = 3.75A

2/ 25A reserved capacity of 155 minutes which gives C=(155/60)(25)=65AH

When I plugged these numbers into the Peukert equations I got a Puerkert
Capacity of 83.3AH, a value of k=1.079 and a capacity C=60AH at a 60A
discharge rate. These numbers match the table for D31's at:

http://www.evconvert.com/tools/evcalc/?s=b

However I am not sure if the Peukert model holds up in practice?

I did actually get 40 minutes plus at 60A from 3/4 of the batteries, so
as Lee suggests it might just be a matter of running them in, and/or
charging them at a higher voltage.

I will get the battery supplier to test that the batteries are
approaching the 25AH capacity with their charger.

Thanks Roland, Lee, & Steve for your kind advice. I also emailed Optima
re the slight swelling and they gave me this reply:

David, 

All sealed lead acid batteries will see a pressure build up
inside the battery when subject to the conditions you describe.
It is normal to a point. If the battery is getting hot (warm
is OK, hot is not) to the touch or if the safety release valves
are opening, then you have an overcharge condition that is
damaging to the battery. 

Thanks, 
Cam 

None of my batteries have ever been warm of shown any sign of venting,
either during charging or during the 200A or the 60A tests, so this
makes me feel a little better.

Cheers,

David



> Roland Wiench wrote:
> > Hello David,
> >
> > The ampere draw out will not match the ampere-hour rating of the battery
> ...


----------



## EVDL List (Jul 27, 2007)

On Tue, 05 Aug 2008 18:55:30 +0930, David Rowe <[email protected]> wrote:


>So I have a couple of questions:
>
>1/ Are these slight bulges a sign of damage? 

Probably not. That's probably just a sign of gas pressure in the cell. If
the bulges become smaller after sitting for a few days, you'll know for sure.

My large rectangular AGMs bulge a tiny bit on the sides after a charge. More
interestingly, after they sit for several weeks without use, the sides and the
top actually suck in from the partial vacuum left as the recombination process
does its thing.

The thing to be cautious of, and something you need to check on is that if
you're building pressure in the battery during charging then you could be
close to venting. Venting IS a life-shortening event. You need to check your
charger to make sure its peak absorption voltage isn't too high. One of the
rather inexpensive DVMs with RS-232 output is handy for that.
>
>2/ Am I naive to expect 60AH @ 60A out of these batteries, or is 40-50AH
>@ 60A reasonable? The Peukert numbers using the D31 data (C=75AH at
>C/20 discharge, and a capacity of 155 minutes at 25AH) suggests 60AH
>however I am not sure if the Peukert model is a real world model.

Yes. As we've discussed fairly frequently, Peukert can't be used to
extrapolate that far. Many high performance AGMs (Hawker Genesis for example)
don't fit Peukert very well. Hawker/Enersys publishes a table of discharge
rate vs duration instead.

I don't like the more than 20% variation between the batteries that aren't
obvious duds. If you've posted it, I don't recall the history of these
batteries. Have they been in storage for awhile? How many cycles? If
they're new but have been in storage for awhile then they may come together
after a few cycles.

Also, I would NOT routinely discharge them to 10.5 volts. That's very hard on
them. I'd go no lower than 11 volts. I have my discharge tester set to stop
at 11.5. That makes the capacity appear to be a bit short but if you look at
the voltage during discharge, by the time it gets to there, it's dropping
pretty fast so there's not much charge left.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
If stupidity hurt then there'd be Aspirin in the salt shakers.

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## EVDL List (Jul 27, 2007)

Hi John,

Thanks for your comments.

> The thing to be cautious of, and something you need to check on is that if
> you're building pressure in the battery during charging then you could be
> close to venting. Venting IS a life-shortening event. You need to check your
> charger to make sure its peak absorption voltage isn't too high. One of the
> rather inexpensive DVMs with RS-232 output is handy for that.

I monitored the charger(s) that I have used around the bulk
current/float switching point and the peak is just 14.1V, probably on
the low side to fully charge these batteries. Don't think this could
damage them as the dealer has suggested. Hopefully he will test the
charger today and agree.

> I don't like the more than 20% variation between the batteries that aren't
> obvious duds. If you've posted it, I don't recall the history of these
> batteries. Have they been in storage for awhile? How many cycles?

The batteries have been in storage for 9 months since purchase. During
that time they had 2 charges using a smart car charger (which peaks at
14.1V) to maintain them. They have then had (i) 250A for 30 sec each, a
charge, then (ii) a full discharge own to 10.6V @ 60A. That's the
entire history.........

> Also, I would NOT routinely discharge them to 10.5 volts. That's very hard on
> them. I'd go no lower than 11 volts.

Agreed - I just wanted a first up characterisation. Between 11.0 and
10.6 was really only the last 10% of capacity anyway.

Thanks again,

David


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## EVDL List (Jul 27, 2007)

>
> The electrochemist I know that use to work for Optima (he doesn't want me to mention his name, because he doesn't have time to answer a lot of questions from the public) said that the bulging I saw (much more dramatic than "slight") on my used/abused yellowtops were an indication that they got overheated at some time, and softened up the plastic. I'm sure that some of mine did get very hot, but I can't imagine that 45C/110F is "too hot"; it's gotta get hotter than that under the hood of an ICE car.
>
> It sounds like you have a very helpful battery dealer that's willing to talk with you and take you seriously.
>
> Steven Ciciora
>
> <snip>
> 
>> > 
>> > One other possibility is that while in storage they
>> > experienced a rather
>> > hot summer, e.g. up to 45C/110F.
>> > 
>> 
> <snip>
>
>
> 
>
> 

Funny, I was gonna say the same thing. Gotta love Polyethylene for it's
chemical and impact resistance but there is a reason we called it
poly-candle-wax.

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## EVDL List (Jul 27, 2007)

Hello,

Just an update on my Optima testing adventures:

Some emails to Optima HQ and a phone call to the Optima distributor for
Australia confirmed that some slight swelling at the top of each cell is
a known characteristic of current D31s - apparently the plastic is a
little weaker at the top of the battery than it has been in the past.
Once my Optima dealer was brought up to speed on this they were happy to
honor the warranty (initially they were concerned I had over-charged and
damaged them). 

The Optima dealer tested my 12 D31 Yellow Tops and found similar results
to me - 3 duds. They were quite surprised as they have had maybe a 1%
failure rate for Optima's over a 10 year sales history. In fact their
returns are so low that I had to explain the warranty conditions to
them!

They apologised for the confusion and cheerfully replaced the 3 duds -
the 3 new batteries check out OK, in fact remarkably consistent at 38AH
each @ 60A. This is at the low end of the other batteries (40-45AH @
60A) but hopefully this will improve with time.

My original batch of Optima's were bought in November 2007, which
matches with a bunch of other bad quality reports on this list.
Hopefully the bad patch is behind them, time will tell.

Thanks again to everyone on this list for their kind help. It has been
a stressful week - especially those few days when the dealer thought I
had destroyed the entire pack due to the swelling issue! This list
really helped me straighten the problem out.

Anyway, back to crimping cables and finishing of this EV 

Cheers,

David



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