I have an RX450h 2010 model.
My dealer says that it is the 12V battery which is the start battery, i.e. which turns the engine when I start the car.
But I have seen several Lexus owners saying that it is the hybrid battery which actually turns the engine,
while the 12V´s function is to make the hybrid system ready for the hybrid battery to kick in.
This is why a small kick-starter is enough when the 12V has gone flat. (Which happens to my car if I leave it unused for 2 weeks, and my dealer says this is to be expected!! My dealer says that I must buy a booster-battery charger which must be connected to the battery every time I park. If I had known this, I would not have bought a Lexus).
Can anyone tell me what actually goes on during the startup process?
