[Oeva-list] over discharged lithium pack

Gary Graunke gary at whitecape.org
Fri May 6 11:25:20 PDT 2011


On Friday, May 06, 2011 11:15:03 AM Ron Jayasuriya wrote:
> I have a customer who accidentally left his car on and ran his 400V Kokum
> battery pack too low, and his charger won't try to charge them now.
> 
> AC Propulsion kit, probably proprietary charger, do not have any specs.
> Car has BMS and balancing, so we will probably be ok once we get them
> charged up somehow.
> 
> Ideas?
> 
> I was thinking that if there were a Rudman PFC 20 out there somewhere I
> might be able to use it to give the pack little boost using the adjustable
> voltage/current feature of that charger.  Not sure for certain, but I
> think I should be able to monitor the batteries for voltage AND heat
> during the process.
> 
> Does this sound reasonable?  Dangerous in any way?  I don't think so, but
> it's worth asking. Anyone with some experience with over-discharged
> lithium batteries, or a PFC-20 they'd let me use, feel free to chime in.
> 
> Thanks!
> 
> Ron
It could be a bit dangerous--be prepared for a dead short. The A123 cells 
become a short circuit if they are allowed to drop below 2 volts for long. No 
idea about the Kokum pack. 

Definitely use a fuse or current limit. You already mentioned monitoring heat, 
but watch out for an explosion as well.

I doubt that the lithium batteries can be brought back as easily as lead acid 
ones. 

Gary



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