LVB Question

[FrankM1]

Scenario: Say your LVB died. You get your power pack and jump to open the Frunk. You then proceed to jump the LVB. The door unlocks and the car starts. My question is: If I remove the jump start on the LVB, will the car keep running? Theoretically the HVB via Converter is supplying about 14 VDC to charge the battery. If this were the case, could I drive off running on the converted power (assuming the vehicle is not turned off)? Would there be enough current to supply the needs of the 12 V system. I, we can come up with a lot of theories but has anybody actually tried this?

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[Maquis]

That’s exactly how mine behaved when the battery died. I didn’t actually drive it anywhere, but I’m sure I could have.
It might be possible for the LVB to fail in such a way that this won’t work. YMMV

 

[Teslaeata]

Provided the LVB didn’t completely discharge and die it should perform just like an ICE battery, and when you turn off will either be sufficiently charged to continue to work or fail to allow you to unlock and start again.

 

[Mach-Lee]

Scenario: Say your LVB died. You get your power pack and jump to open the Frunk.

FYI hopefully the power pack isn't in stored in the Mach-E, otherwise you won't be able to get to it if the LVB dies and the doors are locked.

You then proceed to jump the LVB. The door unlocks and the car starts. My question is: If I remove the jump start on the LVB, will the car keep running?

Once the car is on and you have the green READY status showing, the DC/DC converter will be engaged and powering the 12V systems. So yes, the car will keep running, even if the 12V battery is dead, until you turn it off. It will provide enough current for all the vehicle systems.

The hard part of the process is using the jump pack correctly (must use the override function) to get the frunk open, and to jump the battery at the right moment during a start attempt.

 

[guinn]

I had experience with this, but as they say, your mileage may vary.

This happened between 3 and 4 years ago with my 2021 ME. I came out to the garage, and the car was dead. I finally figured out how to open the frunk and get to the 12V battery. I tried charging it from our gas car, but it didn't do much. I have a battery charger that doesn't work very well, but I put it on the ME. After a while, things started lighting up, but the car wouldn't "start". So, I left the charger on overnight, and the next morning the car seemed to be just fine.

I took the car to the dealership where they diagnosed that the battery was bad. Of course, they didn't have a replacement and had to order one. It took 2 or 3 months before they got the replacement battery. I drove the car without any problems during that time. I'm still not convinced that the original battery was actually bad, but I was willing to let them put a new one in under warranty!

So, from my experience, you might expect the car to work just fine. I would maybe drive around the neighborhood for a little while before going to the dealership.

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