used LiFePo prismatic: what do i check?

[dutchlincoln]

Hello,
I can buy 16 used LiFePo prismatic cells with bms and charger for a reasonable price.
Now my biggest question is, on how to check if they are okay?
How could i check abuse or cycles?
any info welcome, thanks.

 

[Gordo]

The only true way is to load test them over a complete discharge cycle and monitor the Ah supplied before they drop below 3V. You need a graph for that pack and compare your measured Ah to what a new pack does.

 

[dogman dan]

The obvious is any puffed cells, or sweet smelling stink of ruptures. But harder to see that on prismatic boxes than on naked pouches.

Full charge, then watch for an hour would give you some idea of any really bad ones. They'd lose voltage and not seem to stop. Better cells would hold their full charge voltage, or only lose a small bit and then stop. If they don't stop self discharging by 3.5v, I'd say they were toast. but you could have some that only drop to 3.6v overnight, yet have no capacity left.

Lastly, scorchy looking bms would be an indicator of possible damage. I mean scorchy on the bms itself, not just some heat shrink. Heat shrink often melts over good fets that get hot in use.