BZ4X Battery

[Roy124]

Simple question, does the car have a 12v Battery? 

[philip42h]

Yes

[Malop]

From the manual

[adidev]

I always do wonder why EVs need a 12V Battery?

[forkingabout]

4 minutes ago, adidev said:

I always do wonder why EVs need a 12V battery?

To power up the safety contactor that disconnects the high voltage traction Battery from the vehicle electrical system.

The 12 volt system also runs the normal vehicle functions like infotainment, lighting etc.

[ernieb]

It’s a standard between all car and component manufacturers with universal specifications and approvals.

The 12v low voltage is considered safe what else would you use to power the security and accessory systems? 

[adidev]

3 hours ago, ernieb said:

It’s a standard between all car and component manufacturers with universal specifications and approvals.

The 12v low voltage is considered safe what else would you use to power the security and accessory systems? 

The same way your CPU is powered in your laptop - the Battery is, let's say 11.8V, but the CPU only need 1.5V - it's step down and regulated. For safety reason, the disconnect switch should be, in my opinion, energized in fail safe. But, saying all that, there are more cleaver people to judge that, or it might be only due to "old" regulations. I think, a small 12V Battery to provide initial startup of the electronic should be sufficient and manufactures should get rid of that remaining of the ICE.

[Cyker]

It was ostensibly for safety reasons - The high voltage system is not connected when the car is off to stay 'safe', so you need the auxiliary 12v system to power things like the remote locking and HV contactors.

However, Tesla seems to keep their traction batteries always connected in some situations, e.g. if Sentry mode is enabled, so I don't know if there is an actual law requiring this or it was just industry safety convention, that Tesla has decided to ignore.

 

There are some advantages to having the 12v tho', mainly that it is end-user chargeable and replaceable if it dies. If the sole source of power was the traction Battery and it ran out, you'd be stuffed, as you wouldn't even be able to plug it in to a charger, as the ECU needs to do the handshake with the charger before it will start supplying power, which it obviously can't do because it has no power!

With the Toyota hybrids, this would entail lifting it or putting a trolley under it to get it on to a low-loader (Can't disengage the EPB without power!) and taking it to a Toyota dealer where you'd likely have to wait a few weeks to a few months for the special traction Battery charger to be delivered to the dealer so they could charge the Battery. With EVs they'd probably also have to drop the whole battery pack in addition to getting hold of some special external charger for it.

With the 12v tho', even if the traction battery was totally depleted too, you'd just have to charge up the 12v and you'd be back in business to charge the car back up at home or wherever.

 

[Pitkat]

As a follow up. Does any one know the proper procedure to disconnect the 12v Battery? I need to do a hard reset, as my head unit keeps rebooting constantly in a loop.

[TonyHSD]

40 minutes ago, Pitkat said:

As a follow up. Does any one know the proper procedure to disconnect the 12v Battery? I need to do a hard reset, as my head unit keeps rebooting constantly in a loop.

Disconnect the negative terminal for at least 20 min. Then reconnect. It might trigger alarm sound best to have key fob with you. When disconnected the boot hatch won’t be operational and any other lock that uses 12v power.   👍

[Pitkat]

OK, so disconnected the negative terminal 

[TonyHSD]

57 minutes ago, Pitkat said:

OK, so disconnected the negative terminal 

Yes, undo the nut and move the whole cable assembly on the side and make sure no metal object touches the terminal, that’s all . 👍

[Pitkat]

Worked like a charm. now if only I could get the Apple Carplay to connect reliably.

[Derek.w]

Apple carplay try opening you maps on the phone before/after plugin your lead then starting the car.

[aiden1072]

Beware, the 12v runs down fast. I was parked for 1 hr and had the radio on and for awhile the heating. When I tried to start the car fully it wouldn't disengage the handbrake and would not turn on. Luckily I left it turned off  for about 10mins and the 12v recovered just enough to start the car. Lesson is if parked and you need heat or other turn the car on fully and keep in Parked mode.

[Gray86]

51 minutes ago, aiden1072 said:

Beware, the 12v runs down fast. I was parked for 1 hr and had the radio on and for awhile the heating. When I tried to start the car fully it wouldn't disengage the handbrake and would not turn on. Luckily I left it turned off  for about 10mins and the 12v recovered just enough to start the car. Lesson is if parked and you need heat or other turn the car on fully and keep in Parked mode.

*ready mode 👍

[aiden1072]

Yes, sorry, ready to drive mode, but in neutral with parking brake on.