Charging Nimh Battery with the inverter

The series 1 Prius hybrid has an inbuilt inverter that can be used to charge the main nimh battery with a 12 volt battery. This feature was dropped in lter models.

How to charge the nimh battery with the inverter.

1) Connect a 75 ah or larger battery in place of the 12 volt battery. The standard 12 volt battery does noy have enough capacity.
2) Start the vehicle. The nimh 288 volt fault indicator will display.
3) Remove the ignition key
4) Press start on the inverter in the car boot.
5) Charging will start
6) Allow charging to complete
7) Start the vehicle.
8) Let it run to charge the battery completely
9) Reconnect the 12 volt battery

Battery Computer Failure in Series 1 Prius

First indication was when we get a vehicle where the charge monitor went from yellow to half to 3/3 then to full very quickly. It then discharge quickly to yellow with the tortoise low power indicator showing. This quick flickering in charge level is not usual. We always suspected the Nimh battery.
Our recondition process now results in a good working battery - we therefore suspected the computer. Replacing the faulty computer with another fixed the problem. Out of more than 50 batteries reconditioned to date we have encountered about 5.
We think that this could be the result of diode degradation over time. If this is so then all battery computer will have a limited life!! Perhaps someone can shed more light on this.