[EVDL] Abused Lithium Batteries

795 Views 2 Replies 1 Participant Last post by EVDL List, Dec 13, 2010

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Discussion Starter · Dec 12, 2010

I just a got a car in the shop that has 88 - 100ah( Foxx power bms)
lithium batteries ( they look like thunder sky) and I believe, fairly
new. It appears that the car had sat with the DC to DC converter
pumping the amp hours out of these batteries for a long time. The
voltages ranged from zero to 2.5V. The regulators that bolted on top
of the batteries will let the batteries charge up to 3.65V and then
come ON and drain the batteries down to 3.35V. I charged the pack up
carefully, and much to my surprise, all the batteries came up and sat
at 3.3V. After a discharge, I weeded out 5 of the worst ones and was
able to pull 45 ah out of the pack with a slow discharge over a 10
hour period, at which point Voltage was sitting around 3.0V. My
question is:..... what is the best way to try to get these batteries
back to the best of shape? Cycling them, etc. and if they have lost
1/2 of their capacitance, does this mean that they have lost 1/2 of
their cycle life? Or, is it like a lead acid battery that when you
have lost half of your capacitance, you really don't have any cycle
life at all?
One other note... I have an amp hour gauge that I am using (LinkPro)
and as it is set up for Lead Acid batteries, the meter is not reading
zero amp hours, but more along the line of Neg 4 ah after I completely
charge the batteries from their discharge test. I am assuming because
of the 10% overcharge that is required of lead acid batteries and that
this is figured into the meter set up. I bring this up, only to
illustrate that the batteries don't seem to be "leaking" any ah. As
electron containers, they seem pretty good.

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

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Discussion Starter · #2 · Dec 12, 2010

Steve,

Check out the video I posted about (and AMPhibian kindly found the
link I forgot) at
http://jackrickard.blogspot.com/2010/12/what-he-said-what-i-said.html

I need to watch it again but my take is that you won't get any more Ah
back from cycling the batteries.

--
David D. Nelson
http://evalbum.com/1328

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Discussion Starter · #3 · Dec 13, 2010

Being I work with lithium batteries day in and day out I have to agree with the others, there is nothing you can really do to caress the batteries back in to shape. When you over discharge a lithium cell the lithium ions precipitate out of the electrolyte solution and form lithium metal which coats the plates and takes that bit of the plate out of the party. It's not like sulfation where you might be able to get it to turn back in to sulfuric acid, with lithium you would have to physically open up the cell, clean the plates and essentially reactivate it like it were a new cell.

Now if you have a high quality cell manufacturer (cough GBS does this cough) they will take the new cells and after cycle testing their capacity they let them sit at 2.5 volts for about a week because if there is anything that isn't quite right about the cell then the lithium will precipitate out during this time and will show up in a subsequent capacity test before they release the cells for shipping.

Regards,
Ricky Suiter
Elite Power Solutions LLC
92 Saturn SC Conversion, still limping around on lead.

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