alohart
Posts: 1297
Joined: Sat Nov 01, 2014 7:36 pm
Location: Honolulu, HI

Re: Warranty replacement of 12 V battery

Thu Aug 09, 2018 11:05 am

EVBob wrote:suspecting something going on with the dc-dc converter or how the car maintains the 12v batteries.

You could insert an inexpensive 12 V voltmeter into the auxiliary power port below the center of the dashboard. It would clearly indicate when the DC-DC converter is on because the 12 V voltage would be ~14.3 V whereas when it is off, the voltage would drop to the mid to low 12 V range. This could prevent you from being stranded if you see that the 12 V system voltage is dropping below 12.0 V.
Aloha,
Art

2014 BMW i3 Arravani Grey, Giga World, Tech + Driving Assist, Parking Assist, DC Fast Charging, JuiceBox EVSE

EVBob
Posts: 121
Joined: Tue Apr 18, 2017 6:06 am

Re: Warranty replacement of 12 V battery

Thu Aug 09, 2018 11:31 am

Yep...time to get a pair of 12V voltmeters ....

though it was kinda easy to tell the 12v was failing when the center screen started flickering off while on the SOS call :x

jadnashuanh
Posts: 3986
Joined: Thu May 22, 2014 2:07 pm
Location: Nashua, NH USA

Re: Warranty replacement of 12 V battery

Thu Aug 09, 2018 1:31 pm

The distributed computing system relies on a computer message to tell various modules to shut down when you turn the car off. If one or more of them is not getting the signal, it will discharge your battery. If the sensors are not reporting the actual voltage reading of the battery, it won't get charged. A static discharge test should show if the system is drawing excessive power when off. The clock, alarm, and remote entry systems don't use a huge amount of power, and the normal range of discharge is known...it's not that hard to measure, and should point to the problem. It's also not hard to test the DC-DC supply that provides the 12-vdc.
Jim DeBruycker
2011 535i x-drive GT, 2014 i3 BEV

EVBob
Posts: 121
Joined: Tue Apr 18, 2017 6:06 am

Re: Warranty replacement of 12 V battery

Tue Aug 14, 2018 8:59 am

Update on the "battery issue" - After telling them I wont take back the car with just a 12v battery swap (#3), they investigated further and found a power draw....they ordered a BDC to see if it will resolve the issue...hopefully it'll fix the issue...driving around a 7 series loaner feels like I'm going to hit something in the parking lot....that and having to visit the gas station ugh.....

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