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12V Backup Battery

ATPMSD

Member
Mar 12, 2021
346
357
Atlanta, GA
Here is one for the 12V battery gurus out there.

What if a lead is run from the battery to the frunk storage area, like for those who connect a battery tender for long term storage. But in this case in the event of a 12V battery problem, could we connect a second 12V battery to the lead and have a drivable car? This might be a good idea for those taking road trips far from the beaten path. Also, it could be easy to make a run to a battery store to buy a small 12V battery to make do until a proper replacement can be made.

Workable or a really bad idea?
 

tga

Supporting Member
Supporting Member
Apr 8, 2014
4,023
2,990
New Hampshire
Old nosecone cars (pre front end refresh) had a jumper terminal behind the nosecone for this very purpose. You could connect a 12V jumper pack to the terminal which would provide enough power for the computers to boot up and activate the HV relay in the pack and energize the DC-DC converter. After that, the DC-DC converter takes over powering the 12V system and the jumper battery is no longer needed. Everything will work fine until the car turns off turning off the DC-DC converter.
 

DB13S60

New Member
Aug 16, 2021
1
0
thousand oaks ca
Newbie here go easy. So I have the jump pack and it powers up the car well in a test from behind the nose cone. But I question if I'll be able to get into either the frunk or the car if 12v battery is dead. I've read about having a dead key and the tricks to get in but this isn't that. Has anyone here actually had a dead 12v and been able to open the frunk or the car?
 

Snerruc

Active Member
Apr 16, 2016
1,013
1,592
Palm Bay
Newbie here go easy. So I have the jump pack and it powers up the car well in a test from behind the nose cone. But I question if I'll be able to get into either the frunk or the car if 12v battery is dead. I've read about having a dead key and the tricks to get in but this isn't that. Has anyone here actually had a dead 12v and been able to open the frunk or the car?
The cars have a manual opening system. It varies by year and model. Google for your year and model if you can’t find it in the manual.
 

Cobe

Member
Jun 7, 2021
40
39
Van Alstyne, TX
Reviewing the MY manual, is this what you are referencing?


Frunk.JPG
 

Rice&Curry

Member
May 9, 2018
386
201
San Jose
MX has 2 pull cords labelled A and B and you need to pull them one after the another and it will open the trunk and you will be able to access the 12V battery. The car doors will still be locked till you address the 12V battery problem.
 

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