12 volt system

[DavidN57]

I recently came back from a two week holiday to a flat 12 volt Battery. I am about to go away again and wondered if anyone has found a cure, other than having a separate Battery pack to jump start the vehicle? Does adding a schedule to the climate control of MyT start the vehicle so that it will charge the 12v system? There does not seem to be an off option on the climate schedule, just a day/time start and temperature, will it go off after a set period?

[Empty Sea]

This is the main thing that puts me off buying another bZ4X - the unreliable 12V Battery. It has happened to me several times and I have no confidence using long-term airport parking as a result, even though my original Battery stopped holding charge and has been replaced (not under warranty). Many (not just Toyota users) seem to have similar problems with their electric cars, and it is definitely something that Toyota needs to address. But perhaps someone else has found a workaround - other than the de rigueur Battery pack jump start option?

[wivenhoe]

The preconditioning is set for a fixed time in my RZ - 20 mins. I don’t think that scheduling the preconditioning will solve the issue as I think the car doesn’t go into the ‘Ready’ state. Lexus’s answer is to buy a solar charger - I pointed out not much use in an airport multi storey !

[ernieb]

12v Battery issues are up there trying for the number one fault on 'all' makes of EV cars, not just Toyota.

[JonathanP]

It's also not limited to EVs I had a number of issues with my CH-R a few years back, but at the time it was blaimed on Covid and people not being able to go anywhere.
As other people have said with all the extra 'gadgets' which are installed in cars now, maybe the 12v Battery just isn't big enough capacity or something in the car goes and uses more Battery than it should. (Like on a mobile phone when an app decides to just drain the Battery as it's not shut down properly)

[philip42h]

As above, this is a 'feature' of cars with traction batteries - self-charging hybrids and EVs.

Cars when standing have always imposed a drain on the 12V system - more so as electronic systems have got more sophisticated and comprehensive. In the bad old days, a car with an ICE would also be encumbered with a starter motor and a hefty start Battery big enough to turn it over - so the car would pretty much always have sufficient power for the electronics, such as they were, but may not have enough to turn over and start the engine.

Our cars have a much smaller auxiliary Battery that through a longer standing time may discharge so that it is unable to power all the systems required to unlock and/or start the car. The question is then, how long is too long and what can we do about it.

I would argue that the car should always stand for two weeks and be happy to start. Equally, if we plan on leaving it for longer that four weeks we should be expecting trouble. We can do the obvious things like:

• Never use the 12V systems when the car is Off, in Accessory mode or with Ignition On. Always ensure that the car is in Ready mode / On so that the auxiliary Battery can be recharged from the traction battery.
• Make sure that the 12V auxiliary battery is fully charged before we leave it to stand for a longer time.
• Use a trickle charger or solar charger to maintain the battery throughout the standing time - obviously where such is practical.
• Carry a jump starter pack to ensure that we can get going again without having to wait for the breakdown service.

The 12V auxiliary battery is a consumable item - it won't last forever - and we can always look to fitting a slightly larger capacity battery for a longer safe-standing time.

Then there is the situation where despite everything else, the car does not survive a reasonable standing period:

• Check for non-standard accessories that remain connected to the "always live" side of the system.
• There have been recalls to update the DCM module software to ensure that it shuts off correctly - rather than remaining active and running down the battery.
• There have been recalls to replace the DC-DC converter module from a faulty batch that allowed the 12V battery to slowly discharge through the converter.

The known faults are model / batch specific so won't apply in all cases but may be worth checking with the dealer. And, of course, there may be other faults that I haven't yet heard of ... 😉

(I don't believe that there are any real problems with mine, but, nevertheless, I do carry a jump start pack just in case - I've not needed it yet.)

[Andy BZ4x]

I've had my BZ4X for over a year & never had a problem with the 12v Battery

[Mister Mike]

I've had my BZ4X for over 18 months & never had a problem with the 12V Battery.

However, I had a Toyota CHR previously, and the 12V conked out after about 18 months 😞