12V Battery backup question

[generaltso]

I'm not an expert, please explain. How can the car know if I have the key fob if it's dead? Thanks.

It can't. Unless the 12v source you connect energizes the proximity detector, which I highly doubt. I think the best we can hope is that the frunk won't release unless the 12v battery is dead. But I have a feeling that's not the case either. The moral of the store will likely be to not leave anything valuable in the frunk.

Sponsored

 

[stroszek]

I mean if someone is dedicated enough to jump your frunk open they’re probably more likely to smash a window and get access to your whole car (I assume both would trigger the alarm when the 12v is working even if the jump isn’t bypassed).

 

[sockmeister]

We had this same discussion before. I will not be happy if you can pop the drunk with a 12v source when the auxiliary battery is not dead.
If it is that way they might be able to fix it with an OTA. That would make the drunk useless.
Opening the drunk with a dead battery is also in the manual.

I'm not an expert, please explain. How can the car know if I have the key fob if it's dead? Thanks.

I remember the discussion. We may as well let said discussion die then until we all get our hands on the car

Regarding the keyfob, if you energized that frunk circuit by applying 12v to those terminals, it's certainly possible for it to also be energizing a circuit which searches for and authenticates a keyfob.

Honestly, I am not sure which situation I prefer here.

 

[sockmeister]

I mean if someone is dedicated enough to jump your frunk open they’re probably more likely to smash a window and get access to your whole car (I assume both would trigger the alarm when the 12v is working even if the jump isn’t bypassed).

True, unless they were hell-bent on doing it without attracting attention, such as in a parking lot.

 

[ChasingCoral]

I remember the discussion. We may as well let said discussion die then until we all get our hands on the car

Are you implying we need FACTS around here? Say it isn't so! ?

 

[generaltso]

I remember the discussion. We may as well let said discussion die then until we all get our hands on the car

Regarding the keyfob, if you energized that frunk circuit by applying 12v to those terminals, it's certainly possible for it to also be energizing a circuit which searches for and authenticates a keyfob.

Honestly, I am not sure which situation I prefer here.

But if it's going to energize that circuit, it could also energize the doors so you could just get into the cabin and manually pop the frunk. I think it's far more likely that it's just a very simple solenoid that releases the frunk latch when a 12v current is applied. That's it.

 

[sockmeister]

Are you implying we need FACTS around here? So it isn't so! ?

Ok, the first thing I'm going to do when I get mine is try to pop the frunk with an extra 12v battery lol

 

[sockmeister]

But if it's going to energize that circuit, it could also energize the doors so you could just get into the cabin and manually pop the frunk. I think it's far more likely that it's just a very simple solenoid that releases the frunk latch when a 12v current is applied. That's it.

Likely, but not necessarily given. And that also returns us to the original question: Does this only work when the on-board battery is too low to open the frunk by itself, or does it work all the time?

Since we've come full circle here, I am admitting this is pointless and I'll just continue wondering

 

[generaltso]

Likely, but not necessarily given. And that also returns us to the original question: Does this only work when the on-board battery is too low to open the frunk by itself, or does it work all the time?

Since we've come full circle here, I am admitting this is pointless and I'll just continue wondering

Yup, we won't know for sure until somebody gets one and tries it. But we can continue guessing until then. That's pretty much how we've been filling this forum for the past year anyway!

 

[ChasingCoral]

Ok, the first thing I'm going to do when I get mine is try to pop the frunk with an extra 12v battery lol

I'll try a 9V. That's easy to hide someplace in outside the car!

 

[sockmeister]

I'll try a 9V. That's easy to hide someplace in outside the car!

You could actually hide it right inside that little door where the terminals are! Though I'm not so sure that counts as "hiding".
This would REALLY get interesting if even a 9v battery works.

 

[macchiaz-o]

You could actually hide it right inside that little door where the terminals are! Though I'm not so sure that counts as "hiding".
This would REALLY get interesting if even a 9v battery works.

Two 9 volts in series should be more than enough. Maybe there's room for two.

 

[ajmartineau]

So now when I run in the woods all day I have to log around two 9v batteries in my pack so I can get into my dead MME.
1st world problems.

 

[SnBGC]

I know this has been discussed in the past but posting again to see what others are planning (if anything ) to do.

I was thinking of getting a small charging pack to jump the frunk and the 12V battery, and keep it in the trunk or glove box. But if the 12V battery dies when it is parked and locked and NOT at home - there would be no way to open the doors to get into the trunk or glove box. If at home, the charging pack can be in the house but outside of the home - what are the options - I am not seeing any other than calling AAA or get a jump somehow to the frunk and then jump the 12V battery.

I am asking now because of a situation a few days ago - my older teenager who is at school few hours away decided to drive home at 3 AM and found that the ICE car does not do anything nor open doors. Called me, and I walked through how to get the metal key out of the key fob and open the door. I thought perhaps the key fob battery died - after some drama of even figuring out where the metal key fits in, the said teenager failed to open the door. I drove the couple of hours to their school and figured out how to open the doors and then realized that car battery is dead. But because we were able to some how get in, opening the hood and jump starting was not an issue.

This episode made me think about the Mach E and what would have been my options in that situation other than jumping from another helpful person or AAA and my backup 12V battery pack would be of no use.

Any thoughts from experienced or inexperienced folks here?

Very valid concern. Not sure what the sensible answer is.

I suspect the 12v battery may still be able to activate the door poppers even with a low charge. If the 12v battery is so dead that it can't even pop the doors then a portable jump pack probably isnt going to start the car anyway. In that case you are going to need a jump from another vehicle or a new battery.

Curious how much electricity is needed for the door popper.....shouldn't be much.

Interesting question though....

 

[ajmartineau]

The jump pack is just to open the frunk. You could then connect it to the 12v auxiliary battery to turn on the computers in the car. Then your traction battery will charge your 12v battery. Just don't turn on the radio or lights or heat or anything else until it's charged up.
Honestly, the car will warn you for days that you need to replace the 12v battery before this ever happens. It's not a real issue to worry about. Both my Bev’s have their original battery. One is a 2015.

Sponsored