12V Battery backup question

JellyBelly

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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?
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macchiaz-o

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This has been discussed a number of times now. At this point, we're still in wait-and-see mode.

There may or may not be super capacitors in the doors to allow them to open when the 12V battery voltage is too low. (My guess: these are not present in the final design.)

There is a physical key inside of the key fob. There aren't any lock cylinders on the vehicle though. It seems useless.

Maybe there will be a good place to attach a NOCO booster pack within a waterproof container to the underside of the vehicle. Probably not, though.
 
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JellyBelly

JellyBelly

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This has been discussed a number of times now. At this point, we're still in wait-and-see mode.

There may or may not be super capacitors in the doors to allow them to open when the 12V battery voltage is too low. (My guess: these are not present in the final design.)

There is a physical key inside of the key fob. There aren't any lock cylinders on the vehicle though. It seems useless.

Maybe there will be a good place to attach a NOCO booster pack within a waterproof container to the underside of the vehicle. Probably not, though.
Thanks and good to know that I am not totally off base with realization that there are no good options in such a scenario.
 

janitorjim

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figure if you need a "jump" you are going to actually need a tow to either the dealership or charging station so no need to keep anything extra in the car
 

generaltso

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If the super-capacitors don’t exist, your best bet will be to get somebody with another car (and hopefully jumper cables) to give you a jump.
 


Keyk4

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pg 267-269 of the owners manual, but you'd need to have a 12 volt jump box (or something else) outside the vehicle. You can open the frunk by connecting to the two terminal wires under the small removable cover on the front bumper of the vehicle. With the frunk open then you can jump the 12 volt battery which will let you open the doors and start the vehicle. Overly simplified here but there are specific instructions to follow.
 

macchiaz-o

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Oh yeah... one other idea that we need to test out... 9V frunk access.

Store a 9V battery somewhere under the car. In the event of a 12V failure, use the 9V to open the frunk (if that is enough). And store your 12V Li-ion pack in the frunk to jump start the vehicle.
 

Keyk4

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To me this also means don't leave anything valuable in the frunk if the car will be unattended. Anybody with a screwdriver and a power source can open it fairly easily.
 

GoGoGadgetMachE

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Oh yeah... one other idea that we need to test out... 9V frunk access.

Store a 9V battery somewhere under the car. In the event of a 12V failure, use the 9V to open the frunk (if that is enough). And store your 12V Li-ion pack in the frunk to jump start the vehicle.
we just need somewhere to store one of these - it's only 6 pounds.

Ford Mustang Mach-E 12V Battery  backup question 1608597334641
 

CHeil402

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If the 12 V battery is fully dead, your high voltage battery would also have to be basically be dead because there's a DC-DC converter that replaces the traditional function of an alternator, so I don't know if a jump would help get you anywhere just open the doors/hood. Although since it's not used to start an engine you don't need the amperage that another car typically needs to provide, so you might be able to get away with something much less powerful, like a USB battery pack plus an appropriate converter. (Just guessing, don't know for a fact, but activating a relay/solenoid to pop the hood doesn't take a lot of current).
 

CHeil402

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To me this also means don't leave anything valuable in the frunk if the car will be unattended. Anybody with a screwdriver and a power source can open it fairly easily.
I believe this only works if the battery is actually dead, otherwise it's bypassed.
 

RockDaphne98296

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I have the 2017 Ford Fusion Energi PHEV - my car battery died, not the PHEV Battery but the 12V Battery which I found out powers the doors (including the door post keypad). I was a little surprised (and new to PHEVs at the time) that the fact that my BEV Battery was fully charged meant nothing. Long story short - it turned out the Fusion Energi's had a 12 V battery problem - something in the environmental system would run down the battery while parked, so they uploaded a SW patch and replaced my battery under warranty (at the third visit to the dealer for service). Since then I have carried a big fat charger, I chose the fatty boy STANLEY (J509) JUMPiT Portable Power Station Jump Starter: 1000 Peak/500 Instant Amps, USB Port, Battery Clamps because it has an air compressor and other ports to charge your phone (while camping for instance).

I have been wondering the past few months (actually a year now!) if I would continue to carry it in my trunk... it might be a bit of overkill but has come in super handy - I no longer have to risk my car when a friend or coworker needs a jump. This comes from watching my Dad (when I just 21) zap my brand new 1992 Explorer...
 

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Your 12v can die without your pack being dead.
 

macchiaz-o

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If the 12 V battery is fully dead, your high voltage battery would also have to be basically be dead because there's a DC-DC converter that replaces the traditional function of an alternator
Alternatively, the 12V battery is dead because of a chemistry failure within the battery. The big battery won't be able to help out in this case.

In this case, a jumper could successfully allow the car to be driven, by providing the energy needed to close the contactor that enables the big pack to power the motors, etc. This would allow us to drive to the dealer or a store to replace the AGM battery.

I believe this only works if the battery is actually dead, otherwise it's bypassed.
I think we don't know this for sure, yet. Someone will need to test the theory. The owner's manual isn't detailed enough on this topic.
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