Note: I am not a Li-ion cell chemist; (all I know if from the research I did
for the "Battery Management Systems
for Large Lithium-Ion Battery Packs"
In general, Li-ion cells suffer irreversible chemical damage if their OCV
drops below a give threshold (1.9 V for LiFePO4). (Note that a cell can be
below that limit under heavy load, as long as it then snaps back to an OCV
above 1.9 V.)
However, A123 M1 (26650) cells are different and have been shown to not only
survive being discharged to 0, but actually have a lower internal resistance
afterward. I have no knowledge on how that affects their lifetime and
Regardless, all cells will be very badly damaged by reverse voltage.
There is a significant difference depending on how cells are discharged:
1) If cells are discharged by a load across them (a balancer with a high
stand-by current), they will be discharged to 0 V and stop.
2) But is the complete battery is discharged by an external load, the first
cells to reach zero volts will then start charging in the reverse direction
(powered by the cells that still have some voltage), and will be very badly
I believe that in your case (ALM 12V7 batteries) it is situation #1.
Again, just because a cell appears to recover, doesn't mean that its life or
its capacity won't have been reduced.
Please ask Bill Dube' for more insights on this.
View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/A123-ALM-12V7-Batteries-now-charging-tp4656170p4656173.html
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