Hi,
I need to point out that a PHEV-lite it not a trivial problem. Done without a safety shutoff system:
What happens is when the battery is overcharged, it begins to generate gas inside the sealed battery modules. As the batteries generate more gas they also get hot and the vent tries to relieve the pressure. But if (when) the pressure relief vent can't keep up, the cells can expand and bad things happen. In this case, manual monitoring led to the problem.
Understand that the 12 VDC battery in our cars is there to power the control computers. Overcharging the 12 VDC battery does nothing for improving mileage. A plug-in lite puts a small charge on the traction battery, bringing it
SAFELY to a full charge and it must be engineered carefully.
There are at least two protection methods that need to be implemented:
- temperature increase - when any battery module begins to heat, charging must stop, ASAP
- dV drop - during the charging, the battery will reach a peak voltage and then drop by a small amount, ~5mV per cell (See any NiMH datasheet.) Given the large number of cells in a traction battery, hundreds, it is important to find the first one or small group that shows the dV drop to stop charging, ASAP.
These are not trivial
NOR impossible protection systems but they must be part of a properly engineered solution. I don't want to scare anyone, just make sure you understand what must be in a properly engineered system.
Questions?
Bob Wilson