12V Battery Issues

[Empty Sea]

I recently returned from a two week holiday to discover that the 12V Battery of my BZ4X was completely dead. I had left the car completely charged at home, but not plugged into the wallbox. In fact, the 12V Battery was so completely flat that when I tried to recharge it using a smart charger, this just set the alarm off before charging could even begin. Thankfully, a call to Toyota Roadside Assistance (AKA The AA), quickly resulted in a restarted the car.

Unfortunately, the media screen then required a numerical 'security code' before it would allow my settings to appear, although I could drive the car itself. The local dealership did not know what this was, but a savvy technician, before he plugged in his computer, asked if I had tried any codes? I had, but not the obvious: '1234'. Everything then sprang back to life. 

However, it remains a concern that the 12V Battery should drain within two weeks. It doesn't give much confidence to leave the car in an airport car park whilst on holiday! There also seems to be some confusion about whether to leave the car plugged into a wallbox for long periods. The aforementioned technician thought it was the right thing to do, but page 83 of the manual states: "To prevent the 12-volt battery from being discharged, do not leave the charging port lid open or the charging cable connected to the vehicle."  

[Roy124]

Martin, join the 12v club. 

[philip42h]

It's a common feature of Toyota hybrids and will be standard for EVs too. Our cars no longer need a starter Battery - the traction Battery deals with all that - but they do need a 12v auxiliary Battery to keep the electronic systems alive while the car is switched off and then enable them to be turned on again. This is usually a relatively low capacity battery so it is fairly easy to 'flatten' it if you use 12v systems while the car is 'off'.

The bZ4X manual doesn't appear to tell use what capacity battery they use but you would expect it to be sufficient for the car to be left for two weeks. If you left the car for six weeks you / we ought to expect 'trouble'. Many of us now carry a low capacity Li-Ion jump start pack to mitigate this issue - saves calling out the AA etc.

If you had been using the car regularly beforehand it really should have survived a two week 'rest'. It might be worth checking that you didn't / couldn't have left any accessory switched on during that time. And, if not, it might be worth checking whether there is any DCM update pending for your car - over in RAV-land dodgy DCM software has been know to flatten the 12v auxiliary battery in quite a short time ... 😉

[Roy124]

I suspect Martin left his car at home but there are circumstances prior to leaving a car parked up. 

Suppose you are in a car park queue, I am thinking cruise parking, with your car powered off but radio on and frequent powering followed by door opening. 

[Empty Sea]

I've had a couple of plug in Prius', and although there were some 12V Battery issues during the lockdown, neither were so unexpectedly problematic.

So now I'm being inducted into the world of Jump Starters - who would have thought these would be a necessity when spending over £50K on a car? And it seems amazing that such technically 'refined' vehicles still rely on 12 V Battery technology first introduced 70 years ago! (Okay, I know that there have been improvements since then.)

[bZ4X]

This is a well-known problem. Many people believe the first models of Bz4x and Solterra are suffering from this issue because they were left at the port for months!

I read some forums that some poeple could manage to replace it under warranty. 

One example:

[ernieb]

This has been a regular reported problem with the RAV PHEV version especially in colder weather, leaving the car for extended periods.  Many of us carry a small Battery booster in the car so that the car can be mechanically unlocked and the booster connected to just get enough into the 12v system to get the car into the READY mode so that the traction Battery can then charge the 12v Battery.

I also, like other, use a 12v charger in the winer times to top up the battery if I'm only doing short trips or the car is not being used. I have a short adapter cable connected to the 12v battery and simply plug in the charger until it's fully charged. 

With the PHEV Toyota recommended leaving the car in the READY mode for 20 mins if the car was not being regularly used.  I guess there must be read across to the bZ4X?

[bZ4X]

Toyota has to find a solution for this issue:

 

 

[Empty Sea]

So this £76 purchase will hopefully give a little peace of mind. But the video from 'Out of Spec' mentions an European software update. Has anyone in the UK had their car recalled for this?

[bZ4X]

12 hours ago, Empty Sea said:

So this £76 purchase will hopefully give a little peace of mind. But the video from 'Out of Spec' mentions an European software update. Has anyone in the UK had their car recalled for this?

Thats the major update we mentioned in the other topic. Europe received an update and you will need to visit dealer for this to have it done. 

 

"Bz4X Software Bugs, Updates and OTA"