Dead 12v - can you jump start it?

[Brock-WI]

Getting ahead of myself, but I have been dealing with a Nissan Leaf that the 12v dies on randomly about every 6 weeks or so.

So say the 12v is dead on the M3, then I pop the frunk with a 9v (or jump start pack). Then pop the cover off and connect the jump start pack in parallel with the 12v. Does the car then boot up like normal or is there something else to do?

My crazy idea, and tell my why this isn't a good idea, was to put a small SLA or lithium 12v jump start pack in the car, then run that to a hidden switch that would connect them in parallel if the 12v was dead. I was going to use #16 wire so it wouldn't see 12v to 6v when connecting in parallel, but hopefully enough to get the voltage up enough to "start" it. Maybe a weatherproof switch in the tow hitch port?

Dec of 2018 build.

Thoughts?

 

[smatthew]

It depends on why the battery died. Most batteries seem to be developing a bad cell and overheating. If the 12V battery has a bad cell or two, it will act like a load and attaching another battery in parallel may not be powerful enough to raise the voltage to where the car will boot.

In other words, you might have to disconnect the 12V battery, and connect directly to the jump start pack.