I have a 2016 Toyota Auris hybrid and I need to leave it parked in my garage for 3 months. Do I need to take any special precautions? A few years ago I parked my VW polo diesel for 3 months outside in winter weather and when I came home it started right up. The new Toyota has a lot more on board electronics and I'm a bit worried that the 12V battery will drain while I'm away but I am not sure if the drive battery under the back seat will keep the 12V system charged. Should I have a friend come over and drive it around once in a while or is that not necessary?
There are two batteries in Toyota hybrids: the high-voltage traction battery and the 12V battery. You can charge the 12V battery yourself; the high-voltage traction battery can be only charged by Toyota with a special charger. The 12V battery is the first one to deplete as the HV battery is disconnected from the electrical system by using a relay. Both batteries are needed to start the car.
If the 12V battery depletes, you need to recharge, which requires electricity and access to under the hood, requiring functioning mechanical door locks. If the HV battery depletes, you need the 12V battery to be charged to be able to select neutral on the gear selector, so that the car can be moved, and you also need a tow truck to have it towed to the nearest Toyota dealer.
Directly from the Toyota RAV4 hybrid manual (that has a system very similar to Auris):
As the gasoline engine charges the hybrid battery (traction battery), the battery does not need to be charged from an outside source. However, if the vehicle is left parked for a long time the hybrid battery (traction battery) will slowly discharge. For this reason, be sure to drive the vehicle at least once every few months for at least 30 minutes or 10 miles (16 km). If the hybrid battery (traction battery) becomes fully discharged and you are unable to start the hybrid system, contact your Toyota dealer.
Also, in case you have the smart key system:
In the following situations, the smart key system may take some time to unlock the doors. (a) The electronic key has been left in an area of approximately 6 ft. (2 m) of the outside of the vehicle for 10 minutes or longer. (b) The smart key system has not been used for 5 days or longer.
If the smart key system has not been used for 14 days or longer, the doors cannot be unlocked at any doors except the driver’s door. In this case, take hold of the driver’s door handle, or use the wireless remote control or the mechanical key, to unlock the doors.
What I would do is to select the hybrid battery indicator on the screen so that you can see how much charge you have, and drive the car in such a manner that you maximize the charge (usually, utilizing less than 1/4 of the available power uses electric drive, depleting the battery, and pressing the accelerator more than 1/4 to the floor utilizes the engine, charging the battery -- although if you press the accelerator momentarily more than 1/4 and then retract slightly back, it won't switch back to electric drive).
Once you are satisfied that you have full charge on the hybrid battery (except the last two bars that will almost never be filled), turn off the car, wait 1.5 months and repeat. Be sure to leave no map light or anything that might deplete the battery on!
If the car is more than 3-4 years old (yours isn't but somebody else might be reading the same question) and you have never changed the 12V auxiliary battery, I would:
- leave the car parked close to an electrical outlet (so that you can charge the 12V battery if it depletes)
- verify the mechanical locks are working (so that you can get into the car if the 12V battery depletes in order to open the hood)
- change the 1.5 month interval to 0.5 months / two weeks, if you cannot satisfy both (1) and (2) at the same time
And the answer to the HV battery keeping the 12V battery charged: it doesn't, because the HV battery is disconnected from the electrical system by a relay when the car is turned off.
The best option, if you can, is to get someone to come and drive it occasionally - that applies to any car, as it helps to keep the moving parts lubricated, keep the brakes clear, and stops the tyres developing flat spots.
Failing that, I'd suggest connecting a battery conditioner to the 12V battery to keep it topped up, but I don't know whether the drive battery would suffer from the lack of use in the same way that lead-acid ones do.