Bringing LiFePO4 cells back from the dead?

A neighbor ran his 16S LiFePO4 EVE 280 battery bank down to zero while he was gone for an extended period. I am trying to see if it can be brought back to life. I have charged up some of the cells and then tested capacity, and measuring 250-280AH on various cells.

Based on a single test it appears the cells retain significant capacity, although I have no idea of what type of cycle life they will have moving forward (they are 2 years old).

Curious to hear from others that have attempted to revive LiFePO4 batteries that have been totally discharged and what happened when put back into use?

Their internal resistance is likely notably higher than spec. If you have a YR1030 or YR1035+ you can measure the impedance of the individual cells. They are likely over-spec. If not, your neighbor is quite lucky!

Did he discharge them to 0 or did the BMS protect them?

Edit to add I salvaged some cells a while back that were down around 1v, I charged them low and slow and in a few voltage steps. They seem to be working fine though I never capacity tested them.

apctjb said:

Curious to hear from others that have attempted to revive LiFePO4 batteries that have been totally discharged and what happened when put back into use?

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I revive some LFP cells in 2015 who was drop at 0.1V (154V nominal drop at 4V).
Over 384 cells, around 100 was recover and many are still in use today.
Still amazing considering we are talking here about cells build in 2009 and used in a EV for around 50 000km.

yabert said:

I revive some LFP cells in 2015 who was drop at 0.1V (154V nominal drop at 4V).
Over 384 cells, around 100 was recover and many are still in use today.
Still amazing considering we are talking here about cells build in 2009 and used in a EV for around 50 000km.

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I just went through 73 CALB 40Ah cells that I've had for a few years. They had been in an aftermarket plug-in-Prius application - about 10kWh rated total.

Unfortunately, the owner removed the pack when he sold the car. Rather than a BMS, each cell had a balance board on it. Any individual balance board could open a circuit if min/max voltage was exceeded thus signalling the controller to isolate the battery. Unfortunately, those balance boards drained the cells down to about 0.6V. 100% of them recovered to at least 50% capacity. I've had them in storage for a few years since then.

Unfortunately, this round of re-testing yielded disappointing results. I evaluated capacity, internal resistance and self-discharge. I was only comfortable using 48 of them for a ~129Ah 25.6V battery in what amounts to a very low C rate application (0.1C typical). What was truly telling was the internal resistance. Spec was 0.8mΩ and NONE were below 1.2. Since it's low C rate and 6 cells will be in parallel, I'm using cell that are up to 3mΩ. 6P resistance is .21-.30mΩ

This is also a "run whatcha brung" situation... trying to use what I've already purchased.

I was able to recover 48 of the 64 cells. I first charged them slowly at 5A until voltage came up from 0 to 3, then charged them fully at 30A to 3.65V. I did a capacity test then recharged. Capacity of the cells I tested was > 260AH . They are now back in service and working okay. Will be interesting to see how long they last...

How was their IR?

How was their IR?

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Unfortunately don't have a meter to test IR..

apctjb said:

Unfortunately don't have a meter to test IR..

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$50 cheap peace of mind.