For the past few days I have brought up the posibility that the charging of these batteries may be the cause.
It doesn't matter what type of battery is being used. If a battery is depleted of power and a fast charge is implemented there will be problems.
I've had a thermal runaway with NI Cad batteries 3 times.
They can explode if not isolated from the electrical system. In one case we landed and the battery continued to overheat after we isolated the battery in flight.
It may be a simple fix by controlling the output of the charging system.
As I have pointed out before, all these battery problems have been during ground operations from the APU charging system.
Some aircraft took off and quickly noticed the problem.
If after takeoff there is no battery problem then not to worry.