Testing an Aux batt solution...

[Jmitchelltfo]

It could be because a few of us have followed the mad scientist (HammaMan) and swapped our Powerboost Auxiliary battery for an LFP battery.

It's just too tempting to look at the OBDlink dashboard and see 100% SOC

(lower left)

Yup, I’ve done that too. It’s nice to see a 100% SOC and resting voltage of 13.2, vs 12.5 on the OEM setup.

I was just trying to understand why @Porpoise Hork wanted to have two LFP batteries.

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[Porpoise Hork]

Not two, just one with at least 30AH capacity that fit in the OEM location w/o a bunch of cutting or anything like that.

 

[Jmitchelltfo]

Not two, just one with at least 30AH capacity that fit in the OEM location w/o a bunch of cutting or anything like that.

Gotcha.

Looks like some custom 3D printing is in your future then. Good luck with it!

 

[tsigwing]

If anyone wants the stock aux battery that came in my 2025 your welcome to it. Just have to pick it up in DFW.

 

[tsigwing]

Pretty funny how the same concerns pop up for the C8 corvette. Since I put a Bluetooth monitor on my truck I decided to put one on my vette as well. Have never had an issue on the original 4 year old battery.

 

[Snakebitten]

Yep, low voltage battery issues plague a LOT of these fully networked vehicles being produced these days.

Batteries used to be just for cranking the starter. Amps mattered far more than voltage.

That table is upside down now.

 

[kd-]

Installed this mod today and excited to see how it performs - thanks for sharing! My truck started giving me the dreaded "System off to save battery" message so figured I'd try this before replacing the AGM under the hood. Took about 2 hours overall.

The "mini" Eco-Worthy battery HammaMan suggested from Amazon wasn't available, so I ended up purchasing the smallest 30Ah I could find, which was one from DC HOUSE. It allegedly has low temp protection which I liked though it shouldn't be necessary in my climate. It included a few 9AWG wires for free which I wired up in parallel for an effective 6AWG on the positive side using an M5 nut and bolt.

I wasn't able to get the battery up to 14.6V with my bench supply no matter how many times I tried to pull current from it at 14.4V with some LEDs, it wouldn't accept 10mA or 20mA above that voltage, so I just sent it at 14.4V - 0.05V per cell didn't seem like too much, but I guess time will tell.

After mangling up the aux battery box with my oscillating saw while it was in the truck, I decided to remove it and do further modification with a Dremel and the saw. Highly recommend removing the bracket, it's only 2 extra bolts.

Had to modify the lid for the box too:

And it _mostly_ closes, except for the side near the negative terminal - I suppose because it's sticking up there, or because I can't quite cram the measurement CT on the side

edit: I don't recommend the DC HOUSE for this battery, see here

 

[Snakebitten]

Good job!

Don't worry too much about not potentially getting it "balanced" perfectly. I believe you will see 100% SOC for the Ford SOC PID if you drive with the fan-speed at 5(+) for a while.

Once you get that result, you don't need to use 5 continuously. Depending on your driving habits you can use 5 to top it back off if you see the SOC eventually drop to whatever you decide is your bottom. For me it's around 90%.

The best news is that I doubt you will see the battery save mode ever again.

 

[kd-]

Speaking of SoC, has anyone paired this with changing the target SOC in the BCM of forscan from 80% to something else like here - https://www.f150gen14.com/forum/threads/question-about-changing-battery-charge-rate-in-forscan.21552/

Could that reduce the need to do the fan speed 5 hack? Not a huge deal but one fewer thing to remember.

 

[Hans Moleman]

I‘m thinking of jumping into the LFP battery boat but have a few questions:

1. What are the telltale signs that factory 12V aux battery is going bad? My 12V under hood battery was changed early this year by the dealer and I don’t want a bad aux battery to drag it down.

2. Is this Eco Worthy LFP 20Ah battery still the one to get or are there batter options now? https://www.amazon.com/ECO-WORTHY-Rechargeable-Trolling-Mobility-Scooters/dp/B09NB97XGL

3. Can I use the Noco Genius 10 in lithium mode to top off the LFP battery before installing it?

4. If I need to periodically top off the 12V under hood AGM battery, is it ok to use the Noco Genius 10 in AGM mode while the LFP battery is still connected to the truck?

 

[Jmitchelltfo]

@Hans Moleman

1. What are the telltale signs that factory 12V aux battery is going bad? My 12V under hood battery was changed early this year by the dealer and I don’t want a bad aux battery to drag it down.
Warnings on your dash? Not running in EV mode as long or as often as it should.


2. Is this Eco Worthy LFP 20Ah battery still the one to get or are there batter options now? https://www.amazon.com/ECO-WORTHY-Rechargeable-Trolling-Mobility-Scooters/dp/B09NB97XGL
20-30 amp hour LFP batteries with a solid BMS will serve you well. I have no experience with that one, but several others have used it with good results.

3. Can I use the Noco Genius 10 in lithium mode to top off the LFP battery before installing it?
Noco does have a lithium mode on most of their chargers.

4. If I need to periodically top off the 12V under hood AGM battery, is it ok to use the Noco Genius 10 in AGM mode while the LFP battery is still connected to the truck?
It won't hurt to top it off with the charger, but I will say that I haven't used a charger once in the past eight months since adding an LFP parallel to my oem aux battery, but I do run my fan on 5 or higher to constantly charge at a minimum of 13.9 volts.


This is one of those mods that there really isn't a downside......unless you live somewhere frigid and the BMS needs to wait for the battery to come up to temp before accepting a charge every day.

 

[tsigwing]

I‘m thinking of jumping into the LFP battery boat but have a few questions:

1. What are the telltale signs that factory 12V aux battery is going bad? My 12V under hood battery was changed early this year by the dealer and I don’t want a bad aux battery to drag it down.

2. Is this Eco Worthy LFP 20Ah battery still the one to get or are there batter options now? https://www.amazon.com/ECO-WORTHY-Rechargeable-Trolling-Mobility-Scooters/dp/B09NB97XGL

3. Can I use the Noco Genius 10 in lithium mode to top off the LFP battery before installing it?

4. If I need to periodically top off the 12V under hood AGM battery, is it ok to use the Noco Genius 10 in AGM mode while the LFP battery is still connected to the truck?

I have both the Noco and the Eco Worthy. Initially I just installed the eco worthy as is and everything worked just fine. After installing a blue tooth battery monitor I was watching the battery SOC. Never reached 100%, typically around 80, which is fine, but it kinda bugged me. Finally decided to hit it with the NOCO.

I disconnected the aux battery and set my Noco to lithium. Didn't take long for it to reach full charge. While still disconnected, I changed the Noco to AGM, and did the same for the under hood battery.

After sitting all night, took this snapshot this morning.

 

[CaptainAmericaRob]

I'm getting the "some features disabled due to low battery voltage" or something like that.
I installed a new aux battery last year, but the 12v battery under the hood, is the original OEM battery, from 9-15-2021 when truck was built.
i don't drive every day, and have a short 3 mile commute to work.

 

[Porpoise Hork]

I'd seriously consider replacing the main 12v battery as OEM's rarely make it past 3 years. Walmart batteries are much cheaper than the parts houses and well built so they last a long time. When you install the new battery do a BMS reset then put it on charge until your charger reports it's complete. You may also want to look into adding a 20-30AH piggy back battery to the aux battery and if you have not done so already update the state of charge setting with Forscan from 80% to 98-100%.

 

[tsigwing]

I'm getting the "some features disabled due to low battery voltage" or something like that.
I installed a new aux battery last year, but the 12v battery under the hood, is the original OEM battery, from 9-15-2021 when truck was built.
i don't drive every day, and have a short 3 mile commute to work.

My Noco has a battery repair feature. Worth a shot if you have one.

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