# [EVDL] Battery health and charging question



## EVDL List (Jul 27, 2007)

Hello All,

I think I need some help. Here is my setup.

24 6v flooded lead acid (Interstate workaholic back when they were 
made by US Battery)
251 ah at 20 hr rating
Manzanita PFC-30
Zilla 1k controller


Since insulating the box holding 19 batteries, my PFC will on 
occasion continue to put out amps but pack voltage does not rise to 
setpoint, therefor does not shut off. I believe this is called 
thermal runaway. The first time it happened I had the amps set at 25, 
and the batteries were COOKING when I shut the charger off in the 
morning. Since then I have made a number of trips, followed by 
charges. Most of the time voltage rises to setpoint and amps go to 
zero after timer finishes.

However the situation where the charger stays on without reaching the 
setpoint has happened my last few charges (no longer charging at high 
amps).

An additional point is that the battery temperatures vary alot 
(almost 20 deg F) between the large insulated sub-pack and the two 
smaller uninsulated subpacks under the hood.

Does this indicate a bad battery/cell?
Is this normal when battery temperatures vary greatly?
Is 5,200 miles about what I should expect out of this pack of floodies?
Have I murdered my pack?

I have had the entire pack gassing for a few hours, but I am still 
seeing voltage differences. Just now I took 2 specific gravity 
reading. Cells from two batteries in the insulated back had s.g. of 
1.152 and 1.157. The s.g. from a cell from 1.179. This was about 3 
hours after a trip that I thinks consumes about half the useable pack 
capacity.

Any ides appreciated.



Below is a description of the truck history and recent changes made.

I have about 5,200 miles on the pack. For most of these miles I had 
the batteries in two uninsulated plywood boxes, one subpack of 21 in 
the bed of my truck and 3 in a box under the hood.

I had been charging to US Battery specs (2.58 temp adjusted volts) 
and things were good until it started getting cold and performance 
took a nosedive.

Last Sept I took the truck out of service for some upgrades/ 
revisions. I finally got it back on the road early september of this 
year.

One of my revisions was to move two batteries from the truck bed to 
under the hood.
Included in the plan was to insulate each of the now three plywood 
boxes.

I was only able to insulate the box in the bed (now 19 batteries) 
with 2 inch pink board insulation (plus additional lower quality 
insulation to fill space )


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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

I have almost the exact use pattern you described, to the mileage, and range of battery voltage differences.

Since I am unable to get to the Trojan recommended daily setpoints, I have been charging at lower currents and my batteries are not getting as hot, not gassing as much and the end voltage is climbing higher. 

Will an un-balanced pack lead to excessive heat build up?

John



> Wayne Krauth <[email protected]> wrote:
> 
> >
> > I am also wondering about my battery health.
> ...


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## EVDL List (Jul 27, 2007)

When your batts were out of service, did you keep them charged and
desulfated?


Last Sept I took the truck out of service for some upgrades/ 
revisions. I finally got it back on the road early september of this 
year.


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## EVDL List (Jul 27, 2007)

The EV was off the road for only 2 weeks last summer, and had less usage
during dec-feb (not enough cabin heat!), but the battery pack has always
been kept charged and watered. 

I was expecting that as the batteries declined, it would be seen as a
gradual reduction in range. I was not expecting them to run so hot. 
The last drive was only 5-6 miles and the pack temp went up by 10F, to 84. 
Then after recharging for 2-3 hours, the battery temp was down a bit to 82,
but when I next checked it it was over 130F so I unplugged it.

The individual battery voltages are all 8.46v - 8.51v, with one at 8.40v and
one at 8.55v

Is battery overtemp an expected failure mode? or is there any possible
remediation? 

Or could my battery charger be failing and causing the batteries to
overtemp?

Wayne





> EV Convert wrote:
> >
> > When your batts were out of service, did you keep them charged and
> > desulfated?
> ...


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## EVDL List (Jul 27, 2007)

Well they got a regular charge before taking the truck apart, then one charge in the spring. Living in Massachusetts temps were low over the winter.

It could well be they needed a long low amp charge. That seems to have helped.

John



> EV Convert <[email protected]> wrote:
> 
> >
> > When your batts were out of service, did you keep them charged and
> ...


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## EVDL List (Jul 27, 2007)

Hi,
Finally someone who has the same problem I have had. As far as I can find
out it is a problem will all of the new "high tech" chargers and older
batteries. As the batteries age they cannot achieve a maximum voltage
specified and their internal resistance increases. The chargers think the
batteries are not charged and will continue the high (equilization voltages)
indefinitely (or in my case until the water boils off!!). 

I have had both a Zivan NG3 and the Elcon do this when my Trojan 105's
reached about 2/3 of their rated capacity. I replaced the Zivan thinking it
was a problem with the charger. But, when I bought new batteries the
problems disappeared. 

I wish manufactures would include this type of information in the manuals so
won't destroy our batteries.

If you want to run your batteries longer about the only solution for
chargers you cannot program is to put them on a time. 
tom H. 
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## EVDL List (Jul 27, 2007)

> On 22 Oct 2010 at 10:32, Tom H wrote:
> 
> > As far as I can find out it is a problem will all of the new "high
> > tech" chargers and older batteries.
> ...


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## EVDL List (Jul 27, 2007)

> EVDL Administrator wrote:
> > A charger which uses a dv/dt algorithm won't behave this way. Instead of
> > charging until the battery reaches some target voltage (or doesn't), it
> > stops charging when the on-charge voltage is no longer rising.
> ...


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## EVDL List (Jul 27, 2007)

From: Tom H
> As far as I can find
out it is a problem will all of the new "high tech" chargers and older
batteries. As the batteries age they cannot achieve a maximum voltage
specified and their internal resistance increases. The chargers think the
batteries are not charged and will continue the high (equilization voltages)
indefinitely (or in my case until the water boils off!!).<

I think this has been the sad end for many packs . Its seem to happen
without warning , if you catch it you can still get some years on you
pack.


>I have had both a Zivan NG3 and the Elcon do this when my Trojan 105's,,,,,,,
If you want to run your batteries longer about the only solution for
chargers you cannot program is to put them on a time.
tom H.<

One simple fix for chargers you can't adjust might be to put some
diodes in series with the chargers out put . One full wave bridge
would drop 1.4 volts and make the charger think the pack is 1.4 volts
higher that it is, it might take a few to get the end voltage where
you like it . You could even have a relay on a timer to short out the
rectifiers at the first part of the charge then open up and let the
diodes do there voltage dropping . Would need a heat sink and fan ,
but with a timer shorting out the diodes when the amps are high this
might not be such a problem.
Steve Clunn----------------------------


Tomorrows Ride TODAY !
Visit our shop web page at: www.Greenshedconversions.com

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## EVDL List (Jul 27, 2007)

Tom,

Your description seems to summarize my situation well. Although the
batteries are in decline; they seem like they still have about 80% of
original range, so to me, should quite usable for a while longer, for local
driving.

If the charger set points could be reduced to whatever the pack is capable
of now, it seems that the pack life can be stretched out for a while, and
charge and equalize without having it get so hot it. Or is the heating
from internal battery resistance that will occur regardless of a charger
tweak?

I know the Zivan NG3 is factory programmed for a specific pack and charging
curve, but I think there are some trim pots in it that can tweak the voltage
and current set points. On the NG1 it looks like it is 0.8V per turn. 
Can this be done on an NG3? Or is it simply new pack time.

Wayne





> Tom H wrote:
> >
> > Hi,
> > Finally someone who has the same problem I have had. As far as I can find
> ...


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