What's the Frunk Battery for? [Answer: it's the 12v battery]

[davidf01]

Does anyone know what the battery in the Frunk is for?

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[besch2410]

I'm assuming you're talking about the 12V... That battery serves to provide the 12VDC bus power for things like sensors, relays, and switches that are shared with other EV/ICE vehicles. Think about your window up/down buttons, parking sensors, and power for locks. No reason those parts need to be different than an ICE vehicle, and in an ICE vehicle, they utilize the 12VDC bus.

 

[davidf01]

I'm assuming you're talking about the 12V... That battery serves to provide the 12VDC bus power for things like sensors, relays, and switches that are shared with other EV/ICE vehicles. Think about your window up/down buttons, parking sensors, and power for locks. No reason those parts need to be different than an ICE vehicle, and in an ICE vehicle, they utilize the 12VDC bus.

Ah ok that makes sense. I just could not find any information on it.

Thank you

 

[Mr. Flibble]

Ah ok that makes sense. I just could not find any information on it.

Thank you

It is also to boot the computer so that the "engine" will start. Our Kia was left on, and the 12v battery drained. The big EV battery was at about 80% charge.

The car could not start without a jump.

It should be noted, there has since been a software patch that allows the Kia to charge the 12v battery while "idle" which was not the case when it drew down. From what I recall, the Lightning has a similar feature to ensure that the 12v battery does not go dead on you.

 

[cag]

I wanna know how to give someone a jump with the lightning. Pop open the frunk flap and attach cables to the 12V? Or can i maybe use the pro power onboard outlets somehow

 

[Maquis]

The 12V battery runs everything except the drive and the HVAC system. Pretty much the same as an ICE vehicle.

 

[Maquis]

I wanna know how to give someone a jump with the lightning. Pop open the frunk flap and attach cables to the 12V? Or can i maybe use the pro power onboard outlets somehow

Carry a jump pack. The 12V in an EV isn’t designed to provide the cranking power required by an ICE.

 

[sotek2345]

Carry a jump pack. The 12V in an EV isn’t designed to provide the cranking power required by an ICE.

Or a plug in battery charger, jump. We do have those 120V outlets

 

[beatle]

If it's anything like the MachE (and Tesla), the 12v battery will also provide power to close the high voltage battery contacts which provide power to the various systems (DC/DC converter, AC inverters for pro power, HVAC, etc.) Without power, the contacts fail open for safety, and somewhere there is a 12v disconnect that prevents the HV contactors from closing accidentally if you're working on the vehicle. This is also why the car may be "dead" if the 12v battery dies. The DC/DC converter can charge the 12v battery using the power stored in the HV battery, but only if the contactors can close.

https://www.fleet.ford.com/content/...showroom/resources/2021_Mach-E_RescueCard.pdf

This is on page 5:

The high voltage battery system uses a low voltage disconnect plug that opens the 12- volt contactor control supply circuit and is located in the engine compartment. When the service disconnect plug is disconnected the high voltage contactors that supply high voltage to the vehicle are unable to close.​

 

[Crilly]

i hope It is a bigger battery than the Mach-E.

 

[beatle]

12v battery shouldn't need to be that big. It's basically just a buffer between the DC/DC converter and the 12v accessories, though at some point you'd want a larger battery or a second battery in parallel to deliver more current. Ford says you can only add 55A worth of accessories. This thread has some more good info on the 12v battery system with a bulletin from Ford:

https://www.f150lightningforum.com/...–-w-12v-battery-power-and-ground-points.7461/

 

[beatle]

Just got the Tesla Li-ion 12 V battery in my lab to test...only 6.9 Ah! Sorry I won't be able to say how it performed since it is a major OEM that is paying us to run the tests.

I thought the Tesla battery was some kind of bizzarro 14.8v - 16.4v lithium battery?

Ford uses a more standard 35Ah AGM battery and I'm I'm glad for it. Fitting most low voltage accessories in the refreshed Model S / X is a real chore that requires running a second LV battery.

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