Anyone know what small battery under rear seat is for?

[Zyvin]

Hi Zyvin - This is very helpful detail. Do you have a link to this material? I'd love to read more about it.

I bought the service manual and wiring diagrams for my truck. It’s about 18k pages long, lol. It costs less than two tanks of gas and worth every penny.

https://www.factory-manuals.com/expand-2021-ford-f150-repair-manual-3263.html

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[cghall77]

I bought the service manual and wiring diagrams for my truck. It’s about 18k pages long, lol. It costs less than two tanks of gas and worth every penny.

https://www.factory-manuals.com/expand-2021-ford-f150-repair-manual-3263.html

If you have the 36g tank and are in ??, it is cheaper than 1 tank of gas. ?

 

[clfaye]

Thanks Zyvin - I had found that website and wondered if they are legit. It's good to know they are!

 

[Lmarco69]

Do you think it would be okay to use this as a point of power for low draw electronics?

 

[Lmarco69]

Specifically a air bag compressor drawing 7 amps

 

[Harlemox]

Does anyone know if the isolator on these falls to open or closed if there is no power being fed to it?

I'm wondering if I need to worry about this "aux" battery as well if the truck's main battery gets discharged beyond safe limits/etc, i.e. with all of the folks with phantom drain I'm wondering if that phantom drain may have damaged this smaller AGM battery as well.

 

[RJL1400]

Think this is for the 400w power that you can access from the rear truck bed and inside the truck. I have an xlt no powerboost and I have this under my back passenger seat

 

[Kocakchief]

Secondary battery is for ???? maybe....Has anyone disconnected the primary battery to get attempt a reset of the electronics? I disconnected the primary for 30 minutes, once reconnected the electronics acted as if I had done nothing, all the electronic remained as they were. Do the drawing show if there is a switching device for the secondary battery to feed the computers if the primary is disconnected? 30 minutes is too long for a capacitor to cover the blink. Zyvin could you look at the drawings please?
Why I did this, accident destroyed the front speed/radar/whatever sensor in the front bumper, lost all cruise control even thought I still should of had plain vanilla cruise, then was getting this loud tone over the stereo intermittently, no rime or reason. I did the reset on the system screen, got rid of the tone but no cruise control.

 

[travisN000]

I recently came across this video.. a good explanation of the wiring and different uses in the different models:

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