12V Battery Questions

[MikeG]

21 XLT PowerBoost with 40k miles. I have the stock OEM battery that came with the truck and haven't had any issues until I went on vacation for a couple weeks earlier this summer leaving my truck at home and came back to the Ford App telling me battery was low. Truck started up no problem, but I threw a trickle charger on the battery and all was fine for a week and same issue occurred again a week later, and again, and again.

I figured ~3 years is pretty good for an OEM battery, I have no problem replacing it. Just a regular maintenance thing.

However, I am a bit confused by everything I am finding on Google. Some say I need to replace a battery under the passenger seat. Some say I need to reset the BMS after changing the battery out etc. My questions are:

1. Is this a usual symptom of a 12V Battery dying on these trucks and I should replace it?
2. What brand/model battery are you running?
3. Do I need to reset the BMS?
4. Do I need to do anything with the other battery? I didn't even know I had one.

I know I could take it to the dealer, but don't want to lose my truck for half a week for something I could potentially do in my garage in 10 minutes. If I should just take it to the dealer, I will.

Apologies if this topic has been beat to death already.

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[DadBald]

This is a can of worms as you are finding. I still have questions myself, but my take is:

1. Your 2021 battery likely skirted Ford's derated specs. Is it an H7 size? If so then it's probably a decent battery. 3 years may or may not be EOL. Good insurance to replace it, though a good new AGM is not cheap.

2. Ford's 12v battery charging programming is a mystery to all. It does not like to hold it with a high state of charge. The PB especially seems to have reported high stationary energy drain from the battery. If you're at 40-50% charge prior to leaving it for a few weeks, then your situation is explainable whether or not the battery is bad. However, after trickle charging it, I would not have expected continued issues since it probably would have held with a higher SOC bias with a higher starting charge, but this is how my brain thinks it should work, not how it actually does.

3. If you are getting frequent and random "service charging system soon" messages, your best bet is probably to replace the battery. Lots have had success with this approach. There are two recommended "quality" brands - NAPA and one other one (sorry, I went with NAPA, can't remember). Yes you should reset the BMS after installing a new battery. The procedure is: 1) turn on accessory mode (not ignition, not off), and you should see a red battery symbol on the instrument cluster. 2) flash the brights 5 times by pulling the stalk. 3) stomp the brakes 3 times. 4) watch the battery indicator - it will flash a handful of times letting you know the procedure is successful.

What I do not know is if it is recommended to install a new battery at 100% charge or if anything will do. I'm also unclear on how to treat the truck after the BMS reset. I thought I read in the manual that it needs to sit locked, undisturbed for 6-ish hours afterwards to relearn the state of charge. But I have read on the forum of others resetting right before a trip to work in the morning. I also do not know about the small auxiliary battery under the back seat, would love to hear others' take on it. My understanding is it is only used in very specific, short-duration events.

In my case, my OEM battery was 3-4 years old, just like yours, and not causing me any issues. I replaced with a NAPA battery as a preventative measure... and now I'm getting "service charging system soon" messages at random. Very frustrating to cause the issues I was trying to avoid. I've reset the BMS a couple times. I have a battery level logger in the mail right now, gonna try monitoring it over time to maybe find my answers. TBD.

Good luck!

 

[imnuts]

Did it say that the battery was low or that the truck was in deep sleep? Regardless of voltage, the truck will enter deep sleep if there no use after 14 days. If you were gone for 2+ weeks, what you may have seen could be normal.

 

[DadBald]

Yes this could be, but it doesn't explain the issues he's had after charging it when he returned.

 

[Porpoise Hork]

21 XLT PowerBoost with 40k miles. I have the stock OEM battery that came with the truck and haven't had any issues until I went on vacation for a couple weeks earlier this summer leaving my truck at home and came back to the Ford App telling me battery was low. Truck started up no problem, but I threw a trickle charger on the battery and all was fine for a week and same issue occurred again a week later, and again, and again.

I figured ~3 years is pretty good for an OEM battery, I have no problem replacing it. Just a regular maintenance thing.

However, I am a bit confused by everything I am finding on Google. Some say I need to replace a battery under the passenger seat. Some say I need to reset the BMS after changing the battery out etc. My questions are:

1. Is this a usual symptom of a 12V Battery dying on these trucks and I should replace it?
2. What brand/model battery are you running?
3. Do I need to reset the BMS?
4. Do I need to do anything with the other battery? I didn't even know I had one.

I know I could take it to the dealer, but don't want to lose my truck for half a week for something I could potentially do in my garage in 10 minutes. If I should just take it to the dealer, I will.

Apologies if this topic has been beat to death already.

Try resetting the BMS first. I would also go in with Forscan and change the battery State of Charge setting from Ford's 80% to 95% then take it out and put 15-30 miles on it to let it charge the battery up. AGM batteries don't do as well at 80% SoC and most manufactures consider that to be a discharged state for this type of battery. If you do all that and still have issues then replace the 12v battery and reset the BMS again.

You will also find that keeping the SoC at 95% prevents the truck from entering deep sleep for significantly longer periods of time when parked.

 

[Tank]

People seem to forget about the 12v Aux battery under the back seat..
If one battery is dying, then BOTH should be changed...the Main and the Aux.
I came up with a mod to increase the size of the Aux battery from the stock 7.5ah to 14ah.... been running it for over a year, super simple to do, and no issues.

 

[Porpoise Hork]

People seem to forget about the 12v Aux battery under the back seat..
If one battery is dying, then BOTH should be changed...the Main and the Aux.
I came up with a mod to increase the size of the Aux battery from the stock 7.5ah to 14ah.... been running it for over a year, super simple to do, and no issues.

I was considering doing this same thing but only with a 20AH LiFePO4 battery instead.

 

[Henfield]

I have the power inverter under the rear seat, but is the aux battery under the rear linked to the stop/start system? I got lucky and received the factory delete for stop start.

Lets see a photo of the rear seat battery set up.
Thanks

 

[PaulGrun]

Try resetting the BMS first. I would also go in with Forscan and change the battery State of Charge setting from Ford's 80% to 95% then take it out and put 15-30 miles on it to let it charge the battery up. AGM batteries don't do as well at 80% SoC and most manufactures consider that to be a discharged state for this type of battery. If you do all that and still have issues then replace the 12v battery and reset the BMS again.

You will also find that keeping the SoC at 95% prevents the truck from entering deep sleep for significantly longer periods of time when parked.

I have seen no evidence that monkeying with the SOC parameter via Forscan has any appreciable effect on the "low battery" phenomena.
It is not clear that this parameter, despite its name, affects the level of charge at which the BMS maintains the battery, but there is some evidence that the BMS uses that parameter as part of its algorithm for e.g. running a battery de-sulfating phase and/or optimizing battery life.
It seems likely that Ford has largely resolved the "low battery" issues within the past year by updating its charging strategy. They blew it however by not teĺling us what they were doing and why. This has allowed tales of battery problems to fester.
For those who would offer anecdotal evidence of the efficiacy of modifying the SOC parameter using Forscan, I would offer my own anecdotal experience - '22 PB XLT 302A. Not used as a daily driver; my usage model is probably as rough on the battery as you can imagine - the truck sits for days (sometimes weeks), and when it is driven my average trip is well under 5 miles. I have, but don't use, a battery maintainer. I am still running the OEM batteries.
Zero problems.

 

[MikeG]

This is a can of worms as you are finding. I still have questions myself, but my take is:

1. Your 2021 battery likely skirted Ford's derated specs. Is it an H7 size? If so then it's probably a decent battery. 3 years may or may not be EOL. Good insurance to replace it, though a good new AGM is not cheap.

2. Ford's 12v battery charging programming is a mystery to all. It does not like to hold it with a high state of charge. The PB especially seems to have reported high stationary energy drain from the battery. If you're at 40-50% charge prior to leaving it for a few weeks, then your situation is explainable whether or not the battery is bad. However, after trickle charging it, I would not have expected continued issues since it probably would have held with a higher SOC bias with a higher starting charge, but this is how my brain thinks it should work, not how it actually does.

3. If you are getting frequent and random "service charging system soon" messages, your best bet is probably to replace the battery. Lots have had success with this approach. There are two recommended "quality" brands - NAPA and one other one (sorry, I went with NAPA, can't remember). Yes you should reset the BMS after installing a new battery. The procedure is: 1) turn on accessory mode (not ignition, not off), and you should see a red battery symbol on the instrument cluster. 2) flash the brights 5 times by pulling the stalk. 3) stomp the brakes 3 times. 4) watch the battery indicator - it will flash a handful of times letting you know the procedure is successful.

What I do not know is if it is recommended to install a new battery at 100% charge or if anything will do. I'm also unclear on how to treat the truck after the BMS reset. I thought I read in the manual that it needs to sit locked, undisturbed for 6-ish hours afterwards to relearn the state of charge. But I have read on the forum of others resetting right before a trip to work in the morning. I also do not know about the small auxiliary battery under the back seat, would love to hear others' take on it. My understanding is it is only used in very specific, short-duration events.

In my case, my OEM battery was 3-4 years old, just like yours, and not causing me any issues. I replaced with a NAPA battery as a preventative measure... and now I'm getting "service charging system soon" messages at random. Very frustrating to cause the issues I was trying to avoid. I've reset the BMS a couple times. I have a battery level logger in the mail right now, gonna try monitoring it over time to maybe find my answers. TBD.

Good luck!

Thanks for the detailed response! It is an H7.

I just checked with my multimeter and the battery is sitting at 12.26 Volts which based on some charts I am finding on Google seems to not be great for an AGM. I did drive for about an hour yesterday evening, should of been charged. My trickle charger has an App, when I first plugged it in, it said the battery was at 75% charge. So either the truck has a parasitic draw, or the battery is bad?

I am thinking perhaps I should take the battery itself out of the truck, and take it to an auto parts store with my other car and have them test it. This way I can get the battery tested without the aux in parallel to avoid skewed results. May also charge the battery while it's sitting out, and see if it drops down to that 12.26 volts overnight.

I am leaning towards replacing the main battery and Aux just to be safe. Not in a rush though but keeping the Nocoboost close at hand for the time being.

Also wanted to share this video I found on the Aux battery, it's very helpful:

 

[Porpoise Hork]

I have seen no evidence that monkeying with the SOC parameter via Forscan has any appreciable effect on the "low battery" phenomena.
It is not clear that this parameter, despite its name, affects the level of charge at which the BMS maintains the battery, but there is some evidence that the BMS uses that parameter as part of its algorithm for e.g. running a battery de-sulfating phase and/or optimizing battery life.
It seems likely that Ford has largely resolved the "low battery" issues within the past year by updating its charging strategy. They blew it however by not teĺling us what they were doing and why. This has allowed tales of battery problems to fester.
For those who would offer anecdotal evidence of the efficiacy of modifying the SOC parameter using Forscan, I would offer my own anecdotal experience - '22 PB XLT 302A. Not used as a daily driver; my usage model is probably as rough on the battery as you can imagine - the truck sits for days (sometimes weeks), and when it is driven my average trip is well under 5 miles. I have, but don't use, a battery maintainer. I am still running the OEM batteries.
Zero problems.

Like you my average daily trips are considerably short with 3-5 miles dropping my kids off at school. Gotta love working from home. Before increasing the SOC to 95% both trucks would regularly enter deep sleep after a few days of not being driven. The resting voltage on both my 20 Ranger and 22 PB at 80% was 12.40-12.45v compared to 12.8-12.85v at 95% SOC. This may not seem like much of a difference but it does make a considerable difference in the reserve time AGM batteries have. I guess you could consider this anecdotal evidence but the length of time both trucks could sit w/o being started/driven before entering deep sleep or receiving notices that modules were being powered down increased from 3-4 days at Ford's 80% SOC to nearly 12-14 at 95% SOC. You may not have personally seen evidence to support it but from my experience over the past 4 years running at 95% SOC on two completely different trucks has shown a significant improvement in battery live and reduction of startup issues due to modules being shut off to conserve battery charge levels.

 

[Natetroknot]

I can’t believe your battery(s) lasted this long. If it were me I’d replace both and do a BMS reset for sure.

I replaced mine before any sign of trouble at 12k with a size bigger from Wal Mart. They have a great warranty you can get honored anywhere.

 

[Ricksc]

You must be lucky or don’t notice the issues. Mine would hit deep sleep mode weekly. Changed battery and SOC no issues from then on. Truck will start in deep sleep but other features will be turned off. Such as approach lighting, dome lights and remote start.

 

[Tank]

I was considering doing this same thing but only with a 20AH LiFePO4 battery instead.

You can't use Lifepo, it charges differently and our charging system isn't compatible...

 

[Tank]

I can’t believe your battery(s) lasted this long. If it were me I’d replace both and do a BMS reset for sure.

I replaced mine before any sign of trouble at 12k with a size bigger from Wal Mart. They have a great warranty you can get honored anywhere.

I'm actually still on the original battery from when it was built in Feb 2021
It runs at 13.8 to 15.5v.... every day

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