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Recovering large LiFePO4 pack?

963 Views 5 Replies 3 Participants Last post by  john61ct, 
Electric A1
Hey there folks, I just picked up a Ford Ranger EV that was swapped with LiFePO4 about 5-6 years ago, and was parked shortly afterwards and never used again.
I just got a 12v battery in the truck and plugged in the diagnostic tester and got a SOC reading that shows as about 15%. Based on some guesstimation, depending on whether the truck is "set up" as a Lead acid or NiMH that would put the voltage around 290v or 250v respectively.
The LiFePO4 pack in the truck is most likely 105s, though I haven't gotten the chance to open it up yet to see. But taking that into consideration, that would put the average cell voltages around 2.8-2.4v. Based on what I've seen from other people's experiences, they will probably be all over the place with some in the 3v range, and maybe some as low as <1v...
My question is, what do you think the viability of reviving this pack might be, and what method would you go about doing it? I know each cell should be recharged individually, but what should I charge them to, and at what rate should they be charged? Should I capacity test them when I'm done getting them up to voltage?
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J
Might be fine.

Very slowly charge each cell - below .1C up to 3.45.

Goal should be each is just below 3.3V after resting at least an hour, get them all within .01V before putting together all on parallel

Now push them up together to 3.5V let them sit at rest in parallel, say overnight, disconnect and check each one, should be identically charged.

Use that as your baseline for load testing, down to 3V as your zero % SoC.

If they check out, balance again and then rebuild the bank.
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Duncan
I will add some caution to John's answer
Those cells are designed to be supported on both sides
So leave them in the battery box and do the charging/discharging with each cell still being supported on both sides

If you have the cells "naked" then they may swell
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J
Should not be an issue with the very gentle C rate and those conservative voltages.

A little swelling is normal does not necessarily mean damage or mistreatment.

Are these soft pouch type or hard cased?

None of this applies if cylindricals
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Electric A1
john61ct said:
Should not be an issue with the very gentle C rate and those conservative voltages.

A little swelling is normal does not necessarily mean damage or mistreatment.

Are these soft pouch type or hard cased?

None of this applies if cylindricals
Click to expand...
Pretty sure they are hard cased, some sort of "knockoff" Chinese cells. According to the guy I got the truck from, they are not super great cells, but do the job "OK". I'll probably just end up swapping in something a bit more up to date anyways...
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J
I'll take 'em off your hands
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