The small AMG battery under the rear seat on a Powerboost.

[cvretis]

I want to tap into this 12V battery to run a few low amp things (USB, LED lights, etc). Does anyone see a problem with this? It appears to have some sort of amp(?) monitor on the negative lead. I don't want to cause any problems. The idea for using this is (1) don't have to run line through the firewall and (2) if the main system failed, I could still keep phone charged and run my add on LED flashers in the front and rear.

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[Gros Ventre]

Electrically this is doable... But keep in mind that this is a "Keep Alive" Battery designed to power just a few key circuits in the truck's computer memory if you de-energize or disconnect the main 12v battery. I had an experience recently. I took my PB in to do a transmission oil change. The tech made a mistake resulting in the truck refusing to start & move. They troubleshot for nearly 12 hours shop time to include de-energizing the main battery to reset the memory. I spoke with the tech's supervisor about what I believed to be the "Keep Alive" battery. So they tried de-energizing that battery also... Voila! All was well and it ran fine. So could you tap into it? Well yes, but that thought makes me uncomfortable.

 

[cvretis]

Electrically this is doable... But keep in mind that this is a "Keep Alive" Battery designed to power just a few key circuits in the truck's computer memory if you de-energize or disconnect the main 12v battery. I had an experience recently. I took my PB in to do a transmission oil change. The tech made a mistake resulting in the truck refusing to start & move. They troubleshot for nearly 12 hours shop time to include de-energizing the main battery to reset the memory. I spoke with the tech's supervisor about what I believed to be the "Keep Alive" battery. So they tried de-energizing that battery also... Voila! All was well and it ran fine. So could you tap into it? Well yes, but that thought makes me uncomfortable.

Thanks. Now that I know what it is used for, I don't want to mess with it.

Are you from Montana? Thought so with your name.

 

[Lippy]

Electrically this is doable... But keep in mind that this is a "Keep Alive" Battery designed to power just a few key circuits in the truck's computer memory if you de-energize or disconnect the main 12v battery. I had an experience recently. I took my PB in to do a transmission oil change. The tech made a mistake resulting in the truck refusing to start & move. They troubleshot for nearly 12 hours shop time to include de-energizing the main battery to reset the memory. I spoke with the tech's supervisor about what I believed to be the "Keep Alive" battery. So they tried de-energizing that battery also... Voila! All was well and it ran fine. So could you tap into it? Well yes, but that thought makes me uncomfortable.

A little off topic, but why did you change your trans fluid so soon? I usually wait until 50k miles.

 

[Gros Ventre]

I take a long view of maintenance. There is no way they can get all manufacturing residue out of things. So I have taken to changing oils early in order to minimize such stuff floating around in components.

 

[Gros Ventre]

BTW, the transmission Filter for the PB is different than non-PB transmissions, if you go in to have it changed make the dealer check your VIN and get the correct filter. Also it runs nearly $100@. I use AmsOil lubricants. I looked up the specs for AmsOil Transmission fluid. It is not the correct viscosity. So I had Ford fluid put in. So how did that happen? Turns out that Ford & GM jointly developed the 10R80 transmission. GM Specifies a different viscosity for its version than Ford. So, for now I'm using the Ford Transmission fluid.

 

[Bluesman]

A little off topic, but why did you change your trans fluid so soon? I usually wait until 50k miles.

It is considered good practice to change the fluids after the break in period; owners manuals used to call this out as ~ 1,000 miles. You'd be amazed at all the metal particles in the fluids after the initial miles. I've run a patch test on 1,000 mile transmission fluid from my current car and it ran out silver in color. An oil analysis would come back as "too dirty to classify". Consider it a cheap insurance policy if you plan to keep the vehicle long term - engine oil, trans. and differential.

 

[Gros Ventre]

Agreed!

 

[Lippy]

It is considered good practice to change the fluids after the break in period; owners manuals used to call this out as ~ 1,000 miles. You'd be amazed at all the metal particles in the fluids after the initial miles. I've run a patch test on 1,000 mile transmission fluid from my current car and it ran out silver in color. An oil analysis would come back as "too dirty to classify". Consider it a cheap insurance policy if you plan to keep the vehicle long term - engine oil, trans. and differential.

Did you have to drop the pan and flush the lines and cooler?

 

[Bluesman]

Did you have to drop the pan and flush the lines and cooler?

I've only done pan drops on the trans., a basic bleed and feed is all you're doing. You can also suck it out the dip tube.

 

[Gros Ventre]

If you go to change the transmission oil & filter yourself... Be careful. According to my dealer, it is not a simple pan drop. There is some significant interference that must be moved to drop the pan... If I have it right in order for the pan to clear the filter and remove it, you have to remove the interference.

 

[Merlin]

I want to tap into this 12V battery to run a few low amp things (USB, LED lights, etc). Does anyone see a problem with this? It appears to have some sort of amp(?) monitor on the negative lead. I don't want to cause any problems. The idea for using this is (1) don't have to run line through the firewall and (2) if the main system failed, I could still keep phone charged and run my add on LED flashers in the front and rear.

Looks like a larger, higher capacity battery would fit in this tray. Has anyone done that?

 

[Micho523]

Looks like a larger, higher capacity battery would fit in this tray. Has anyone done that?

Some models/trims have two batteries in this tray.

 

[HammaMan]

Looks like a larger, higher capacity battery would fit in this tray. Has anyone done that?

Yes, you can put another of the same, but total capacity is 7ah usable (3.5ah/ea). I've got a 30ah LFP in there that keeps my under-hood at 100% SOC but REQUIRES the HVAC blower to stay on setting 5 or higher to charge else the battery is consumed. Because there are certain variables that are not optional for this use case, I don't suggest someone putting an LFP in there.

 

[Mash150]

@HammaMan, I would like to have a look at this battery, but for the life of me, I cannot figure out how to remove the case. I believe there are tabs at the side but I can’t seem to get them to do anything, but I might be looking in the wrong place. Suggestions, pictures would be wonderful .

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