bobo
Posts: 30
Joined: Wed Jun 05, 2019 4:07 pm
Location: CA/OR border

little 12v battery under hood

Wed Jun 05, 2019 4:11 pm

I am a new owner. Completely new the the EV world!
What is that little 12 volt battery under the hood for? Thanks

davemausner
Posts: 2
Joined: Wed Jun 05, 2019 5:40 pm

Re: little 12v battery under hood

Wed Jun 05, 2019 5:48 pm

It powers the computer systems and the infotainment devices. If the little 12V ever goes dead, you will not be able to start your Bolt !

Whilst plugged-in, the Bolt will top-up the 12V battery when necessary. When not plugged-in, the Bolt will top-up the 12V once in a while, provided the big battery is mostly charged.

A brand-new Bolt may have a damaged OEM 12V battery because it's been sitting in the dealer's lot for months without topping-up. Sometimes it will develop a bad cell, and you have less than 12V to power the computer. The console display will warn you about this.

Be nice to your little 12V !!

SeanNelson
Posts: 1437
Joined: Tue Jul 05, 2016 2:43 am
Location: Vancouver, BC

Re: little 12v battery under hood

Wed Jun 05, 2019 9:20 pm

davemausner wrote:It powers the computer systems and the infotainment devices....

...while the car is turned off. When the car is turned on that power comes from the main 60 kWh battery. But the computers still need to run when the car is turned off to provide things like Internet connectivity (i.e., remote fob commands via cell phone app), recognize key fobs to unlock the car, etc. etc.

bobo
Posts: 30
Joined: Wed Jun 05, 2019 4:07 pm
Location: CA/OR border

Re: little 12v battery under hood

Thu Jun 06, 2019 12:10 am

Thank you.
Maybe to be on the safe side I should replace this battery every so often?
I think the ave battery lasts about 5 years.
So... say every 2 1/2 years? Would be cheap insurance?
What do you think?

theothertom
Posts: 47
Joined: Wed Sep 19, 2018 4:13 pm

Re: little 12v battery under hood

Thu Jun 06, 2019 12:23 am

Most everything in the car works off the 12V battery....lights, heat, radio, wipers, A/C, computer, etc. Of course the drive motor works off the main battery. There's a lot of discussion about how to check the 12V battery, but it seems that it doesn't give warning when it dies. And when it dies, your car won't start. So replacing it early is a good idea.
Edit: Check out this thread on the 12V battery
viewtopic.php?f=10&t=8505

bobo
Posts: 30
Joined: Wed Jun 05, 2019 4:07 pm
Location: CA/OR border

Re: little 12v battery under hood

Thu Jun 06, 2019 12:47 am

Thanks for link. Good read. :ugeek:

WetEV
Moderator
Posts: 393
Joined: Sun Jan 03, 2016 1:26 pm
Location: Near Seattle

Re: little 12v battery under hood

Thu Jun 06, 2019 1:40 am

theothertom wrote:Most everything in the car works off the 12V battery....lights, heat, radio, wipers, A/C, computer, etc. Of course the drive motor works off the main battery. There's a lot of discussion about how to check the 12V battery, but it seems that it doesn't give warning when it dies. And when it dies, your car won't start. So replacing it early is a good idea.
Edit: Check out this thread on the 12V battery
viewtopic.php?f=10&t=8505


Heater works on the drive battery. Has to, due to 5 kW / 12 V is far too many Amps (416 A!).
#49 on the LEAF 100 mile club.
Most everything around here is wet during the rainy season. And the rainy season is long.
2012 Leaf SL Red
2014 Leaf SL Red
Can't sit in a Bolt seat, hoping for better soon.
Or perhaps a Buick version? Buick Electra 225???

SeanNelson
Posts: 1437
Joined: Tue Jul 05, 2016 2:43 am
Location: Vancouver, BC

Re: little 12v battery under hood

Thu Jun 06, 2019 5:04 am

theothertom wrote:Most everything in the car works off the 12V battery....lights, heat, radio, wipers, A/C, computer, etc.

To be clear, 12V power comes from the high voltage battery via an inverter when the car is turned on. The 12V battery is only there to provide the power needed for baseline functions when the car is turned off.

bobo
Posts: 30
Joined: Wed Jun 05, 2019 4:07 pm
Location: CA/OR border

Re: little 12v battery under hood

Thu Jun 06, 2019 1:03 pm

Thanks. That does clear it up for me.
So, my Bolt has a 12V inverter.
Do you have any idea what the input voltage is from the "drive" batteries?

SparkEVPilot
Posts: 105
Joined: Thu Feb 02, 2017 4:42 am
Location: Manteca, California

Re: little 12v battery under hood

Thu Jun 06, 2019 2:08 pm

bobo wrote:Thanks. That does clear it up for me.
So, my Bolt has a 12V inverter.
Do you have any idea what the input voltage is from the "drive" batteries?

The HV battery is about 400 volts DC.

One suggestion I found for keeping your 12 volt battery healthy is this - once a month fully charge your 12 volt battery over night. The 12 volt battery used in the Bolt and Spark EV is an AGM battery and requires a special charger. I am using a BatteryMINDer model 2012 AGM. This charger has an option that allows you to charge through the OBD2 port below the dash by the hood release. I also purchased a couple of extension cables that allow me to mount the charger on a wall by a 120 VAC outlet. This way I just have to pull the cable to the car, drop the window a bit and plug into the OBD2 connector. I has been working great.

Return to “Batteries and Charging”