Originally Posted by
Lemain
It's bollocks, actually, as everyone with a car knows. Where the battery technology is very sensitive to reverse polarity a shunt diode is placed across the cell. Anyway none of this is an acceptable reason for fires and fumes.
You can't compare these battery technologies so easily. They are very different.
While NiCd or lead acid batteries simply terminated service when severely mistreated in the way described, LiIon batteries really take it personal.
And respond by throwing flames.
Edit: The Problem is not reverse polarity but overcharging. At about 10% Over -Voltage (corresponds to ~30 - 50% in capacity) it tends to become critical but that varies quite significantly between different cell types..
This is why you normally use balancers for each individual cell.
Overcharging beyond a certain threshold damages the chemistry (the separator becomes electrically conducting) leading to an internal short circuit. Since the separator between the layers is (highly) flammable this will cause ignition of the cell if sufficient energy is stored in the cell, which is the case when fully charged. Self ignition is possible when charged > 40-50% with most Lithium cells (except Lithium Iron Phosphate).
Is it a known fact that they Charge 8 cells in a row without balancer and cut-off?