Storage of LifePO4 cells empty

[squowse]

I've accidentally/negligently done this for a few Lishen cells.

Charging them up now the voltage seems to be rising really quickly on one or two of them. Like up to 3.5-3.6 with only a few 5-10 Ah in there (as far as I can tell at the moment).

Obviously I'll persist and see what charge I can get in to them and do a discharge test.

Any advice on this scenario - slow charge, fast charge, over voltage undervoltage etc?

I don't need telling how stupid I've been - I have learnt my lesson and will take the financial hit. But I suppose I'm going to be told anyway.

More information - they were stored for almost 6 months unconnected and the voltage when I got them out again was just under 3V.

Thanks

 

[Steve_S]

You can charge each cell or in a SET (top balance mode). You did not mention the capacity of the cells but in any case you can charge them to 3.200 FIRST and allow the Amperage to decrease to <1.5A taken, then let them sit for 12 hours and do a voltage & IR test on each cell to see where they are at... They will most likely have settled a bit lower which is normal.

IF they are close together then you can continue to charge Higher to 3.600 (no need to goto 3.650) and allow charge to decrease again to below 2A ad let sit and retest voltage & IR.

IF NOT Close together, then reapply 3.200 Volts and again charge to <1.5A taken and let sit 2 hours without charge and retest (they should show improvement) IF NOT, isolate cells that do not improve... They will need a cycle - discharge to 2.500-2.600 and then Charge again to 3.200 <1A and retest as noted above.

Do NOT exceed 0.25C charging from dead empty AND ensure cells are at Room Temperature (above 20C but below 30C) before starting.
A Good Quality Bench Powersupply capable of CC (Constant Current) which charges to 90% and CV (Constant Voltage) which finishes off with decreasing current to 100% Full at Set Target Voltage.

Hope it helps, Good Luck

 

[meetyg]

If I understand your question correctly, your cells are in very low voltage.
In order to safely charge them up, you should slowly charge them up to a low voltage (say 2.5-2.8v) with very little amperage (lets say up to 1 amp).
Then, when they reach this voltage, with no more current flowing to them, you can charge up to a higher voltage.
I have seen this recommendation before, but can't recall currently where I saw/read this...

 

[squowse]

You can charge each cell or in a SET (top balance mode). You did not mention the capacity of the cells but in any case you can charge them to 3.200 FIRST and allow the Amperage to decrease to <1.5A taken, then let them sit for 12 hours and do a voltage & IR test on each cell to see where they are at... They will most likely have settled a bit lower which is normal.

IF they are close together then you can continue to charge Higher to 3.600 (no need to goto 3.650) and allow charge to decrease again to below 2A ad let sit and retest voltage & IR.

IF NOT Close together, then reapply 3.200 Volts and again charge to <1.5A taken and let sit 2 hours without charge and retest (they should show improvement) IF NOT, isolate cells that do not improve... They will need a cycle - discharge to 2.500-2.600 and then Charge again to 3.200 <1A and retest as noted above.

Do NOT exceed 0.25C charging from dead empty AND ensure cells are at Room Temperature (above 20C but below 30C) before starting.
A Good Quality Bench Powersupply capable of CC (Constant Current) which charges to 90% and CV (Constant Voltage) which finishes off with decreasing current to 100% Full at Set Target Voltage.

Hope it helps, Good Luck

thanks i'll try that

 

[squowse]

If I understand your question correctly, your cells are in very low voltage.
In order to safely charge them up, you should slowly charge them up to a low voltage (say 2.5-2.8v) with very little amperage (lets say up to 1 amp).
Then, when they reach this voltage, with no more current flowing to them, you can charge up to a higher voltage.
I have seen this recommendation before, but can't recall currently where I saw/read this...

They're just under 3V. They would have been discharged to 2.5V but voltage springs back.

 

[Steve_S]

If the cells are all hovering around 3 Volts then just charge the pack up. I'm sorry I was thinking you had them down to 2 Volts... Hadn't gotten to Coffee 1 yet...

 

[squowse]

If the cells are all hovering around 3 Volts then just charge the pack up. I'm sorry I was thinking you had them down to 2 Volts... Hadn't gotten to Coffee 1 yet...

Seem to be ok ish. Just 1 cell giving me problems now