If not, how does the 12v battery get charged? Do the traction batteries charge the 12v. I wonder as I was washing my car today with the radio on. Would the 12v battery eventually drain the traction batteries and the car wouldn't be able to start?

No, alternator. It have invertor to step down for 12V. Invertor only works with ignition on, so not to worry about running down the traction battery with radio. I sometimes wonder, why did they ever put the 12V battery?

So what happens if the 12v battery runs down? Will the electric motor or ICE still start off of the traction battery? What happens if the car sits for a long time and the traction battery runs down?

With run down battery, your smart key sensor wont work, hence car wont start. You have to boost as regular car. If you run down traction battery, you have to get it towed to dealer, no way around it.

If the 12v battery runs down, then computer won't work and your car won't start without some sort of boost to boot up computer. Since computer needs about 10 amps, even AA battery pack will be enough as long as it has 12 volts. In normal use computer will not allow traction battery to go dead. If the car sits unused for very long time (my guess would be at least 3 months) then you would need to call tow truck and get Toyota recharge traction battery. But I would imagine if the traction battery was fully charged and in good shape then even after full year it should have enough charge to start the ICE. If the traction battery don't hold the charge then something is wrong.

Toyota calls it a generator/motor. I found this site that shows a picture of the motor. I think its encased in where most front wheel drive transmissions go in the rear of the engine.

Our local toyota tech calls that small 45ah battery, the instrument battery. It powers the instruments and I would think the ECU. There may be a very slight drain on it when the car is not in use. The ECU should go into the sleep mode. I'm sure its on enough to watch for the keyless entry and the press brake, start button sequence.

I saw somewhere the small instrument battery gets it's 'slow' charge from the large hv battery. Even when the car is parked overnight.

Here is a site with some very good information. Click on the links at the bottom of the page for more views and info.

http://www.hybridsynergydrive.com/en...rid_motor.html

This is not true. It only gets charged when the system is on. The traction battery is completely disconnected when the system is off. This protects the traction battery from being discharged.

You are correct. The 12 volt battery is charged when the car is in use.

The manual says the 12 volt battery depletes after 14 days of non use. I can see this with the ECU being in it's normal sleep mode when the car is not driven.

I see lots of talk about jumping from another car to start a discharged 12 volt battery. Looks like the use of a 1 or 2 amp charger with intelligence would work as well. I see this battery is a very slow charge and discharge type AGM (absorbed glass mat) battery.

Don't beleive everything you read or hear, I was overseas for close to two months and battery was fine.

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VW TDI--48
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