I'm not buying it. No way a Goodyear shop would be able to tell you one of your major hybrid components is bad. Plus, your dash would be lighting up with warnings and the hybrid system would probably not work at all if one of the motor-generators was bad.
I have read that the 12V battery gets charged from the hybrid battery pack instead of an alternator. The motor-generators are used for powering the wheels, starting the engine, and regenerating power, and aren't directly connected to the 12V battery. The 12V battery just powers the various ECUs, electronics, and lights and does not start the engine.
I don't think any traditional battery charging test (for non-hybrids) is going to be accurate for an RX400h. You would need to see a Lexus/Toyota hybrid tech at the dealer.
Maybe you have a loose connection between the 12V battery and the hybrid battery pack (or whichever cable it uses to recharge), or it is simply due to the colder weather, or it sat for too long between starts and the battery drained.
Last edited by maseace; 12-07-13 at 02:14 PM.