Testing an Aux batt solution...

[CaptainAmericaRob]

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%.

We shouldnt have to do all this extra work just to keep the battery going. The vehicles charging system should be able to keep optimum charge, no matter how you drive the vehicle.
Ford Engineers know the extra demand on the batteries in todays vehicles... they should engineer them accordingly.
i'll be replacing the main battery next week, hopefully that solves the issue.

Sponsored

 

[Porpoise Hork]

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

Most modern AGM chargers have that functionality these days, but I personally would not be all that optimistic on it being able much of any help for a 4+ year old Motocraft battery.

We shouldnt have to do all this extra work just to keep the battery going. The vehicles charging system should be able to keep optimum charge, no matter how you drive the vehicle.
Ford Engineers know the extra demand on the batteries in todays vehicles... they should engineer them accordingly.
i'll be replacing the main battery next week, hopefully that solves the issue.

The reason for putting it on the charger is most new batteries will not be at a full 100% SOC off the shelf. You don't necessarily have to charge it right away but it certainly won't hurt anything if you do. As for resetting the BMS anytime you replace the battery Ford recommends resetting it. It keeps a record of how long it has been since the last reset and after 3+ years it knows the AGM battery is aging and will not have the same reserve as a new one and may likely put modules into deep sleep to protect the battery from being drained too far causing damage. When you reset the BMS it can update the correct baseline for the new battery. Otherwise the deep sleep issues could persist.


BMS reset process.
Turn the ignition or accessory power ON (don't start the engine).
Flash the high beam headlights five times.
Press the brake pedal three times.
Watch the battery icon on the dash; it should begin flashing, indicating a successful BMS reset.

This should be done within 10-20 seconds of the key on into accessory.

 

[FriedCheese]

Thanks to the time saved by all the research here, I decided to redirect it to modelling a 3D printed replacement box. I still have some changes to make, including a lid that will hook into the back, but it's drivable.

I'm guessing I can't post pictures because of being a new member, so I posted them to Imgur.

This reuses the two main bolts that held the OEM box in place and I've done some simple plugs for the other passthrough holes printed in TPU. The little blocks are for clearance under the battery and allows airflow, with a few having a wall to keep the battery in place. I place to have similar walls on the lid as well.

The fuse setup for the positive terminal did pose a challenge so I did the same as another with two jumpers of 8 awg.

 

[kd-]

After having this installed for a few weeks, I think I either got a defective 12V LFP from DC House, or my under-hood AGM is significantly degraded. Despite charging everything up in the truck via bench supply to ~14.6V for 6+ hours then float charging for another 24 hours at 13.8V, my resting voltage is 12.8 - 12.9V after a few hours of non-use.

According to most 12V LFP charts I've found online, this is only 20-30% full on the LFP side which seems bad long term vs the low 13.x range at 40-70% state of charge

I didn't do an extensive bench test of the LFP battery, so that might be my first step. Other option would be to get the under-hood AGM tested somewhere (making sure it's disconnected first!). Anyone else have the same problem other other ideas?

edit: I think I figured this out, see here

 

[Snakebitten]

12.9V resting is probably going to give the truck a pretty high SOC by Ford's onboard PID.

It IS probably a sign of the 12V AGM under the hood drawing down on the LFP, but I don't think it's necessarily indicative of a bad LFP. And 12.9V is definitely ample voltage for the trucks electronics to behave stable.

I know it's tempting to achieve a nice 13.2V resting, since it is commonly reported with this forum Powerboost battery hack. But that's pretty much the ceiling and requires a multitude of ingredients to come together perfectly.

 

[Mszczewski]

Thanks to the time saved by all the research here, I decided to redirect it to modelling a 3D printed replacement box. I still have some changes to make, including a lid that will hook into the back, but it's drivable.

I'm guessing I can't post pictures because of being a new member, so I posted them to Imgur.

This reuses the two main bolts that held the OEM box in place and I've done some simple plugs for the other passthrough holes printed in TPU. The little blocks are for clearance under the battery and allows airflow, with a few having a wall to keep the battery in place. I place to have similar walls on the lid as well.

The fuse setup for the positive terminal did pose a challenge so I did the same as another with two jumpers of 8 awg.

Any chance you'll make your model for the box and lid available to the rest of us on the forum?

 

[FriedCheese]

Any chance you'll make your model for the box and lid available to the rest of us on the forum?

Definitely, but I will forewarn that the long side is 317mm so you'll need a large format printer. There are services that'll print for you but I'm not sure what the cost would be.

But, I'm going to be delayed. After doing the battery swap and getting the initial box printed, my first drive and I've got a grinding sound coming from the transmission tunnel. So, I'll have to drop the truck off at the shop this week for however long.

 

[Porpoise Hork]

Really nice design on it. Simple and clean. I like it and cant wait for the STL's to get posted.

For smaller format printers a couple minor tweaks to the design might be instead of having the three raised supports in the middle make is a solid bar. Then split the tray in half and put holes for nuts and bolts to mate the two sides and run glue along the seam. For the lid could also split it in half with a notch overlap to clue the two top pieces together to form a single piece.

Alternatively just post the STL's as is and anyone with a smaller printer can simply split the tray and lid with their slicer and print the pieces out separately then bond the parts with glue.

 

[UGADawg96]

Well, after 45 months of ownership and many between the ear pep talks to go the lithium routes from this thread, I wussed out and picked these two up yesterday. Precharged them with the Noco and they're going in today.

 

[KBKEITH]

Well, after 45 months of ownership and many between the ear pep talks to go the lithium routes from this thread, I wussed out and picked these two up yesterday. Precharged them with the Noco and they're going in today.

That EverStart is exactly the one I dropped into my 2025 PB. So far, so good.

 

[UGADawg96]

Well, after 45 months of ownership and many between the ear pep talks to go the lithium routes from this thread, I wussed out and picked these two up yesterday. Precharged them with the Noco and they're going in today.

Installed and BMS reset.

 

[Kodiak]

Installed and BMS reset.

HA! That Everstart Plat is the one I got too. I considered X2 but went with the Everstart due to availability everywhere. I did change to the larger AGM O'Rielly's for the aux but not the LFP.

I figured I would rather replace the battery combo regularly (if not early) due to the PB and all the tech eating up a battery more than in the olden days. I get 3 to 4 years and I will be happy.

 

[Samson16]

We shouldnt have to do all this extra work just to keep the battery going. The vehicles charging system should be able to keep optimum charge, no matter how you drive the vehicle.
Ford Engineers know the extra demand on the batteries in todays vehicles... they should engineer them accordingly.
i'll be replacing the main battery next week, hopefully that solves the issue.

I have a 22 PB with the original batteries. They’re behaving just like my other vehicles, but they are all driven regularly. When/if that situation changes I’ll put vehicles less driven on tenders. Seems like good sense

 

[Porpoise Hork]

Guess it's time to replace the main AUX battery?

Several times now both before and after adding the piggyback 20AH battery the 12v SOC has randomly dropped overnight from 100% to 75-90% after a couple weeks of not budging off 100%. Another thing I have also seen happen is the HV battery SOC was at 50-60% at key off but also fell to 35-37% causing the truck to use the flywheel starter in those instances. Not sure what would cause such a massive drain on the system overnight when no updates hit at those times. It has only ever had this happen overnight and never during the day even if the truck sat untouched for close to 10 hours.

Then this morning I get an alert that the 12v battery may not be healthy enough to start the vehicle despite it reporting 100% SOC and having just had it on charge yesterday to run a 12 hour desulfation cycle since I don't drive it all that much. The primary 12v battery is relatively new at just over a year old but the main AUX battery is nearing 4 years old. I'll be replacing the aux battery probably this weekend but I think it rather odd for it to do this even with the additional 20AH battery connected.

 

[JMoney17$]

I was having low battery for awhile I believe and then got the 12 volt warning in the app which led me to take action.

I had previously replaced the original battery shortly after purchasing my '23 powerboats with an H7 battery. It is probably 2-2.5 years old.

After the warning I replaced the Aux battery with the larger Aux battery discussed in this thread. I charged it fully as I did for the main 12 volt battery under the hood. (I pulled the main AGM battery and charged it outside the truck. I reinstalled everything and reset the battery monitoring system)

I decided to go with the lithium battery as well. I purchased a 12V 30 Ah battery from DC house with low temp protection.
https://www.dchousepower.com/produc...e-lifepo4-lithium-low-temp-protection-battery

I charged the lithium battery with a 12v charger I purchased from DC house.
https://www.dchousepower.com/products/12v-10a-ac-to-dc-lifepo4-portable-battery-charger

I hooked the lithium battery in parallel with the AUX battery under the passenger seat.

My voltage went up to 13.2 as seen with other people in this thread.

I drove for the next few days making short trips of roughly 10-20 minutes several times a day. I used Fan 5 setting.

After about 3-4 days my voltage dropped down to 12.8 volts.

I pulled the lithium battery and charged it again last night and reinstalled it. Voltage went from 12.8 to 13.1-13.2.

Would this suggest that the main 12V battery under my hood is at end of life and not maintaining charge? I did not go through the trouble of balancing the lithium battery but I don't know if that is necessary. Appreciate any suggestions before I start throwing more money at the problem.

Sponsored