Thorallophon
Posts: 30
Joined: Sun Jul 22, 2018 4:18 pm
Location: Ottawa, Canada

12v Battery monitoring

Sun Jan 31, 2021 12:31 pm

Hi all,
thought I would comment on 12v battery State of Charge loss after hearing from EV owners like tesla, leaf, and others about the 12v battery when left for long periods of time. I gather it's worse with the new vw id3.

So, I was wondering why vw doesn't have a gauge or have the info listed in the infotainment system? ICE cars have (had?) them, why get rid of that parameter/gauge, especially when it's so critical to the cars function?

Anyway, I'm sure you've seen them, but there is a handy little device that connects to the poles of your battery, and via bluetooth to an app on your phone (see the video below or search online for battery monitor. Amazon has some for around $30-$50 CAD). Gives you a consumption timeline graph if you're interested in charge loss over a 24hr period. Very handy. Very interesting.

I was able to see that my 2017 loss when parked, and not plugged in, over a 4 day period was quite a bit more than I thought. Not sure if weather temp was a factor, but it was cold. The 12v battery went from 98% to 69% SOC over those four days, where the main pack didn't seem to change. I can now understand if someone was parked for more than a week at an airport or something that they might have issues "starting" or even getting access to the vehicle.

I found a youtube video with someone with an id3 using one of these devices, and how they were monitoring its SOC.

Just thought I'd pass this along, as I found it very informative and helpful.
Jon.

https://www.youtube.com/watch?v=jUgOozT ... ex=31&t=2s
2017 e-Golf

f1geek
Posts: 827
Joined: Fri Jan 23, 2015 1:18 pm
Location: SF Bay Area

Re: 12v Battery monitoring

Sun Jan 31, 2021 3:02 pm

I have left my car parked and untouched for weeks at a time with no I’ll effects. It was not super cold. There is a way to view 12 V battery voltage from the gauge cluster, but I don’t remember how. I know the 12 V battery gets charged when driving or charging, but I wonder how many e-Golf owners have had dead 12V batteries in 2020 when many people were stuck at home for extended periods.
2017 e-Golf LE, Multi Coat White with Black Vegan Leather interior

flyboy320
Posts: 63
Joined: Sat May 13, 2017 8:38 am
Location: Toronto, Canada

Re: 12v Battery monitoring

Tue Feb 02, 2021 11:02 am

It would be interesting to watch the discharge with and without the alarm system active. I have heard that with the car locked and the alarm active it uses more battery as a result. Having said that my car sat idle for over a month and when I checked codes with OBDeleven it showed a fault that the battery bus voltage was 11,9v. No error lights on the dahs about the 12v or having to drive to charge, just saw this fault in the app when i scanned the car.

f1geek
Posts: 827
Joined: Fri Jan 23, 2015 1:18 pm
Location: SF Bay Area

Re: 12v Battery monitoring

Wed Feb 03, 2021 10:46 am

Would using a lithium ion 12 V battery solve the problem?
2017 e-Golf LE, Multi Coat White with Black Vegan Leather interior

Thorallophon
Posts: 30
Joined: Sun Jul 22, 2018 4:18 pm
Location: Ottawa, Canada

Re: 12v Battery monitoring

Wed Feb 03, 2021 6:35 pm

Interesting idea, though I think the lead acid battery may be better designed to be drained and recharged to 100% (and kept there).

Also, I have to admit that the little monitor I installed may not be the best when it comes to measuring battery level. So the numbers I gave earlier should probably taken with a grain of salt.

Be that as it may, it still shows regular battery consumption for about 15mins regularly overnight when I assume nothing should be running (car locked, not plugged in, no warm-up program running). The alarm and little flashing LED's and such would vampire drain for sure, but the "big drain" wouldn't be that, I don't think, would it?
2017 e-Golf

manybees
Posts: 142
Joined: Sat Nov 17, 2018 5:08 pm
Location: Boston area, MA

Re: 12v Battery monitoring

Fri Feb 12, 2021 3:15 pm

I just use a USB charging adapter in the 12 v socket in the console. It has an LED readout of the voltage from the 12v battery:

https://www.amazon.com/gp/product/B08138GVMH/

Image
2018 VW e-Golf SEL Premium (w/ DAP) - Silver White w/ black interior

BomBoi
Posts: 64
Joined: Sun Apr 23, 2017 1:45 am
Location: Daly City, CA
Contact: Website Google+ Twitter YouTube

Re: 12v Battery monitoring

Tue Mar 23, 2021 4:44 pm

Awesome find manybees. I will definitely get one of these when switching to an Li battery.
17 e-Golf SE Urano Grey
01 Porsche 996TT Speed Yellow

Return to “General / Main e-Golf Owners Forum”