Frazzybell

Mark, Gen1 cells should not be used. They are known for not holding capacity well and in general are very aged. The Alphard has Gen2 cells as standard within. You can replace cells with other gen2 cells however please note the ECU tolerances for each of the 15No. blocks is very tight. Swapping out cells is bad engineering practice, you will just make the next set of cells the weakest. Furthermore you overcharge the better cells to charge up weaker cells, making them expand and dissipate excess energy as heat. Heating up the whole pack and getting caught in a cycle.. killing itself faster.

The issue you are most likely having is some of the cells within the HV battery becoming much weaker and having less capacity as the others. They are all connected in series like a chain, and therefore only as strong as it's weakest link. When put under load the whole pack voltage will drop and the weaker cells will drop quicker. Due to this the overall voltage of the pack drops too low and the sensor wire on each of the 2 cells ( 15 blocks ) detects this. Resetting via the 12V battery taken off for 5 mins will help get the car started again but when the closes circuit voltage is to low the inverter will not take the HVDC and convert to 3P AC to power the motor.