Testing installed batteries

[todd.martin]

I thought I would share some tips I learned while working on my Force.

Recently, my Force would no longer take a charge.  The old charger (Brusa NLG4), would slowly pump up the pack to about 175 volts (a nominal 156V pack), but when trying to drive anywhere, the volt meter would drop to about 145 volts under load.  The car was then almost immediately in "limp home" mode.

At first, I thought this was a charger related issue.  After all, the batteries are supposed to be charged up to 190+ volts.  The new charger (Brusa NLG5) quickly charged the pack to 190+ volts.  But again, when trying to drive anywhere, the volt meter would drop to 145 volts under load and the car again was in "limp home" mode.  Curiously, the regen wasn't able to put much charge back into the batteries (they acted as if they were full).

Suspecting a bad battery or two, I opened the battery boxes and attempted to diagnose.

With a full charge, all of the batteries showed a good voltage reading.  This is known as the "OCV" or open circuit voltage.

I then turned on the electric heater and the headlights, letting them run for 20 minutes.  With an electric load running, I then re-tested each battery and found one which was at 0 volts on my meter.

When testing the batteries, it was not necessary to take the batteries out of the car or to disconnect them from the string.  You simply place your multi-meter's leads to the positive and negative terminals of each individual battery.

I have now ordered a replacement battery.  Over the winter, I twice drove the car down to its "limp home mode" from silly decisions or mistakes on my part.  This likely caused the battery issue.

Best regards,

Todd Martin

[rich.rezny]

We have at work an interesting electronic battery and charging system checker.  It measures resistance of the battery and has a internal database that computes the battery capacity.  It only works on 12 volt batteries or 2-6volt batteries in series. I wonder how accurate it would be testing a battery in string such as the one in EV's.  If you're ever by the shop, stop in so we can try it out.  Rich

[rick.mouche]

Thanks for the suggestions.  I think I will try running the car a few miles and then check the voltage across each battery.  I did purchase a battery load tester and tested each battery individually.  They all showed a slightly "weak" condition, but none were "bad".  Good news is that my company - Nalco Company, is letting me plug into the 110v stations used for block heaters for the winter snow removal equipment, so no problem with getting a recharge while at work.  As part of our companies "Sustainabilty" effort, there are plans in the works to install high level EV charging stations in reserved spots very close to the building.  I guess I am just a little bit ahead of the time.

I have flooded batteries.  I think I may have overcharged them during the winter (car in storage but I had a little charge on the batteries every few days).  They may have sulfonated.  I read that one can desulfonate these flooded batteries by exchanging the acid for DI and charging them for a while then replacing with new acid.  Anyone tried this or other means.  May give my battery life back. 

[ricky.hazen]

"Back in the day" (it's been 'a few' yrs) - when I used to service battery powered 'portable X-Ray' machines which used 'flooded' lead acid batteries . . . . . (3 packs, each with 30 - 1.25V batts in series {apx 110VDC})
If you let them set for 'X' period of time with out being used, the batteries would develope a thing called a "memory window" (brief explaination is kinda like - if batt holds 100V but has not been used enough to get lower then 85V, the batt thinks it is empty at 85V = "memory window".)
How to cure memory? - Deep cycle discharge the batts to 'EMPTY'.
We used to put something like a '1.2Kw load' (8 - 150W flood lamps in series) on them - then put 'shorting straps' on over night. - then remove shorting straps and recharge to full. As I recall we used to put something like a (1K ohm 150W? - it was big -) load resister (current limiter) on the 'B+' side of the batt pack prior to starting the recharge cycle for maybe about a half to an hour to prevent the 'surge current' form tripping the safety breaker.
This might be effective on the 1st cycle *or* it may require several cycles to 'erase the memory', after which batts 'should' function 'normally' again - barring any other issues (ie - open/shorted cells, loose connections or . . . ).
~Joyfull EVing~

[michael.henry]

Hi all,
 Now that I'm charging my EV on a regular basis, I thought I would read through the forum posts on batteries again. I also have a 156v pack, 13 Trojan t1275's. Charger is a Zivan NG3.
 Full charge for the pack is around 167v. Individual batteries reading from 12.75 to 12.9. Only been through about 10 cycles or so.
 Question :  Is it your contention that full charge should read 175v or even 190v? I did get a value of 192v once, but the battery in my DMM was run down, and I just figured it was an anomaly.
 Water level in the batteries is good. Should I recheck my battery connections?
 Oh, and what's that smell? It's not very strong, but there is a slight odor during the recharge. Normal?

                                                            Thanks, Mike