12 volt battery success ?

[Old Aviator]

I changed to Sodium not long after I started getting "shut down to protect battery" (or something like that). Took 20 mins and then ran the BMS reset procedure. To be sure I also have a Fisker which can be a 12v nightmare, so I'm somewhat attuned to having 250 miles of range but no way to start the car. Seems EV batteries were all undersized under the mistaken belief the HV charge system would protect them, which has not been the case since the HV won't operate without 12v power to operate it. Interesting I have Sodium in both vehicles and have had ZERO battery issues beyond the fact that training the Fisker BMS to work properly is hit or miss and seems to require 3 or 4 iterations before it works properly. Other Fisker owners have not been so lucky and I'm using one I bought off Alibaba for half the price of those sold in the US.

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[rickersondon]

The simple 12v voltage devices the plug in the cigarette lighter work fine for monitor the battery state.

 

[carys98]

I had the bad BMS originally and had a lot of issues with OTAs before it was replaced. I knew my 12V had been through hell so as I got close to 36 months I started monitoring the SOC. It would rarely get over 70%. About 3 weeks before the warranty ran out I took it to the dealer and told them to test it. It failed their test and I got a warranty replacement. If you are near the end of your 36/36 warranty I would recommend you get your battery tested. It’s about a 45 minute test so if they come back sooner than that they did not do the correct test.

 

[chl]

I have gotten 14+ years out of vehicle batteries by doing one simple thing: keeping them on a battery maintainer trickle charger all the time when not using the vehicle.

So I have my 2023 Lightning Pro on one in the AGM mode.

---more info---
I keep my 12v battery on a trickle charger/battery maintainer with an AGM mode to avoid premature death (its, not mine) and to ensure OTAs get installed..

Deep discharge, which the lightning algorithm allows, is not good for longevity of these batteries, and the high charging currents seen when the battery is low, are another bad feature of the lightning system of 12v battery management.

This post form the Mach-e forum goes into depth about these 12v AGM batteries:

https://www.macheforum.com/site/threads/how-to-recondition-service-your-12v-battery.11069/


If the details about how AGM battery charging progresses are accurate, the truck will not, on it's own, top off the battery in many cases because of the time it takes. That makes a trickle charger even more important for longevity since it can be on the 12v battery for many hours at a time charging even when the truck HV is not.


And this one about the different ways to charge up the battery to get OTAs:

https://www.macheforum.com/site/threads/how-to-get-failed-otas-to-install.29749/

Also several threads here about putting trickle chargers on the battery and how to make it easier by adding a trickle charger wire:

https://www.f150lightningforum.com/forum/threads/charging-12v-battery.16979/

This is what I did - I put a wire with an SAE plug on one end through a small hole I drilled next to the charge port hinge where it would not damage anything, and ran it to the battery compartment where I attached it to a fused wire with ring terminals that would fit the 6mm bolts:

 

[djwildstar]

I have read endless posts regarding issues related to the failure or change out of the 12 V battery. Who can share a success story? Has anyone been able to change out the 12v battery in advance of issues and have a seamless replacement without any issues at all?

I recently (Christmas 2025) replaced the 12V battery in my 2023 ER Lariat.

Based on my experience, I expect that your truck is good until 2027, maybe longer. If you're really worried, or in a place where you don't have decent auto-parts availability, then consider doing a swap on your truck's 3-year anniversary. Strictly speaking, that's not needed if you carry a (charged) NOCO Jump Box and your keyfob. This will let you self-rescue if the 12V fails, and you can use it to jumpstart other vehicles. That way, you can wait to replace the battery until the truck starts showing symptoms.

I got my truck in May 2023. It was one of the ones with the bad 12V BMS sensor module, so I suspect that it wasn't accurately monitoring the 12V for the first 18 months or so. By fall 2025, I was getting symptoms that the 12V battery was getting marginal. I would get the "old school" warning chimes if the truck had been sitting (not driving or not charging) for more than a couple of days, and I occasionally got the "system off to save battery" notice on the center console.

In October, this was happening often enough that I ran the truck (parked and locked, with climate control off and the power-down timer disabled) in my driveway for 6 hours to make sure that the 12V was fully charged. This mostly addressed the issue. However, as I was getting ready for a Christmas trip from Atlanta to just shy of Detroit to visit my wife's sister and her family, I got another warning: The truck went into Deep Sleep mode while sitting in the driveway, waiting to charge to 100% for the next day's departure. I went outside and was successful in waking it up and starting the charge.

However, midway through the trip, temperatures had dropped considerably compared to Atlanta, and I was getting low 12V symptoms even with the truck was on. Finally, I had trouble starting a fast charger (one of the new Mercedes-Benz ones at a Buc-Ees). The truck wouldn't start the fast charger, and threw a whole sequence of errors, including locking the transmission in Park. I was able to get it reset, started, and when I plugged in with the truck "running" I was able to start the fast charge.

I left the truck running for fast charges for the rest of the day, and that was successful: I was able to fast charge, and had no problems plugging in to the L2 charger at our en-route hotel that night. I carry a NOCO jump box under the back seat so I was confident I could jump-start the truck if necessary, but my wife was worried about getting stuck with a dead 12V because her sister lives out in the boonies.

I was able to locate an Advance Auto Parts on our route that had the correct 12V in stock. Then I had to locate a second one, because the salesperson dropped only battery at the first one. It cracked badly and was leaking (unusable). Swapping the battery was easy and straightforward, and we finished the drive. I reset the truck's 12V BMS at the hotel that night, and didn't have any trouble for the rest of the trip.

Based on this, I plan to swap the 12V battery in my Lightning (and in my wife's Mach-E) every 3 years as preventative maintenance. While 12V AGM batteries should last 2-6 years in EV use, here in Atlanta (where summers can get hot), they tend to fail sooner. This should be straightforward DIY maintenance, and I suspect that in a non-emergency situation, I can find new batteries for significantly less than Advance Auto Parts charges.

 

[fhteagle]

Success story? Sort of. I swapped the OEM 12V for an Ohmmu Sodium Ion. That stopped the "System off to save battery" on the big touchscreen and "Battery Saver Active" messages in the Ford Pro App ... for about 60 days. The last straw for me was getting a false "Alarm triggered due to frunk" message in FordPass last night and coming out to a completely dead truck this morning. No problem, I thought, I will just manually enable my EVSE and the truck will wake up and start charging both the 12V and HVB like my Volt used to do. NOPE. J1772 provides a modest 12V source across control pilot and protective earth (ground), but not designed to provide any real amperage. That 12V should at least be enough voltage to chain load up some modules to get the truck to a charging state at least, if they were engineered well. But Ford, once again, has completely failed to understand EVs and how they are used in the real world.

I am at the point where I will call Ford's 12V maintenance / charging strategy in my '22 _complete_ _trash_. Because it is. Modules stay alive after the truck is parked/off and will drain the ~35Ah reserve capacity in less than 2 hours!. Then, the truck does not intervene and start pushing power into the 12V until its down to 11.2V sometimes! That is _ridiculous_ , and way too close to the truck goes into 3 ton paperweight voltage level.

Fortunately, I have a very nice jump pack and kept my old OEM battery charged in the garage. But neither of which should be necessary. ~131kWh usable in the main pack but we cant keep ~0.5kWh of 12V alive? C'mon, @Ford Motor Company ....

 

[djwildstar]

I swapped the OEM 12V for an Ohmmu Sodium Ion. That stopped the "System off to save battery" on the big touchscreen and "Battery Saver Active" messages in the Ford Pro App ... for about 60 days. The last straw for me was getting a false "Alarm triggered due to frunk" message in FordPass last night and coming out to a completely dead truck this morning.

I've heard several reports like this.

From all accounts, the Ford 12V battery management system doesn't understand anything other than the OEM 12V 35Ah (H3-XEV) battery. The BMS tracks the state of charge in the 12V battery, and tries to keep it "nearly full", roughly 90%, or around 31Ah. The problem is that the Ohmmu batteries are typically ~150Ah capacity, so the Ford BMS routinely undercharges them -- the state of charge will drop to about 20% and that's where the truck will keep it, believing that the battery is "full".

Better logic in the 12V BMS would address the problem of 12V battery failure without having to go to exotic chemistries. The ideal solution would be for Ford to keep the DC-to-DC converter powered-up for longer when plugged in, even after the high-voltage battery was fully charged, to top off the 12V if and when needed.

 

[fhteagle]

The BMS tracks the state of charge in the 12V battery, and tries to keep it "nearly full", roughly 90%, or around 31Ah.

If I am reading what you are saying correctly, and the Ford 12V BMS is trying to do coulomb counting based charge management, that's an expensive and complicated solution that a simple voltage based solution would do far better. Preventing vampire drain then becomes about actually getting things to turn off sufficiently, instead of playing "how many Ah are left" living on the edge games....

the Ohmmu batteries are typically ~150Ah capacity, so the Ford BMS routinely undercharges them

Is this for the Ohmmu LFP, Ohmmu Na-Ion, or both? My understanding was the Na-ion were sized with closer to the 35Ah RC for this reason. But I could have been misinformed about that before my purchase.

Anybody know the part numbers for the '22 12V BMS or DC-DC converter, and/or for the one in the '24 and up?

I want to investigate the possibility of swapping into the newer part number. But the parts desk guy at the local dealer had no idea what he was looking for, so he couldn't even spit out a price for said part.

 

[Henryw]

I have read endless posts regarding issues related to the failure or change out of the 12 V battery. Who can share a success story? Has anyone been able to change out the 12v battery in advance of issues and have a seamless replacement without any issues at all? My 2024 lightning flash (16,000 miles) green machine is the best vehicle I have ever driven. I want to keep it that way. Should I have my 12v battery tested? Should I just order a new one and put it in my self. What is the secret to avoiding all of these problems regarding the 12V. (foto: free L3 charging c/o Jackson Hole WY : ) Thanks

My 2023 12 volt with 48,000 on shows 93% according to the dealership. Truck was sitting in Fords lot before checking on my frunk issue. Your dealer service desk can see a number of stats on your truck remotely. It was pretty cool seeing the details on the desktop.

 

[chl]

I recently (Christmas 2025) replaced the 12V battery in my 2023 ER Lariat.

Based on my experience, I expect that your truck is good until 2027, maybe longer. If you're really worried, or in a place where you don't have decent auto-parts availability, then consider doing a swap on your truck's 3-year anniversary. Strictly speaking, that's not needed if you carry a (charged) NOCO Jump Box and your keyfob. This will let you self-rescue if the 12V fails, and you can use it to jumpstart other vehicles. That way, you can wait to replace the battery until the truck starts showing symptoms.

I got my truck in May 2023. It was one of the ones with the bad 12V BMS sensor module, so I suspect that it wasn't accurately monitoring the 12V for the first 18 months or so. By fall 2025, I was getting symptoms that the 12V battery was getting marginal. I would get the "old school" warning chimes if the truck had been sitting (not driving or not charging) for more than a couple of days, and I occasionally got the "system off to save battery" notice on the center console.

In October, this was happening often enough that I ran the truck (parked and locked, with climate control off and the power-down timer disabled) in my driveway for 6 hours to make sure that the 12V was fully charged. This mostly addressed the issue. However, as I was getting ready for a Christmas trip from Atlanta to just shy of Detroit to visit my wife's sister and her family, I got another warning: The truck went into Deep Sleep mode while sitting in the driveway, waiting to charge to 100% for the next day's departure. I went outside and was successful in waking it up and starting the charge.

However, midway through the trip, temperatures had dropped considerably compared to Atlanta, and I was getting low 12V symptoms even with the truck was on. Finally, I had trouble starting a fast charger (one of the new Mercedes-Benz ones at a Buc-Ees). The truck wouldn't start the fast charger, and threw a whole sequence of errors, including locking the transmission in Park. I was able to get it reset, started, and when I plugged in with the truck "running" I was able to start the fast charge.

I left the truck running for fast charges for the rest of the day, and that was successful: I was able to fast charge, and had no problems plugging in to the L2 charger at our en-route hotel that night. I carry a NOCO jump box under the back seat so I was confident I could jump-start the truck if necessary, but my wife was worried about getting stuck with a dead 12V because her sister lives out in the boonies.

I was able to locate an Advance Auto Parts on our route that had the correct 12V in stock. Then I had to locate a second one, because the salesperson dropped only battery at the first one. It cracked badly and was leaking (unusable). Swapping the battery was easy and straightforward, and we finished the drive. I reset the truck's 12V BMS at the hotel that night, and didn't have any trouble for the rest of the trip.

Based on this, I plan to swap the 12V battery in my Lightning (and in my wife's Mach-E) every 3 years as preventative maintenance. While 12V AGM batteries should last 2-6 years in EV use, here in Atlanta (where summers can get hot), they tend to fail sooner. This should be straightforward DIY maintenance, and I suspect that in a non-emergency situation, I can find new batteries for significantly less than Advance Auto Parts charges.

Put the new battery on a battery charger maintainer...you won't be disappointed in the life extension that can provide.

The Lightning management system apparently 1) does not adequately top off the LV battery, 2) allows the LV battery to get deeply discharged and 3) uses relatively high currents to charge the battery, all three of these result in shortened battery life span.

Lead-acid batteries last long if kept at 100% when not in use. Just a fact.

 

[chl]

I've heard several reports like this.

From all accounts, the Ford 12V battery management system doesn't understand anything other than the OEM 12V 35Ah (H3-XEV) battery. The BMS tracks the state of charge in the 12V battery, and tries to keep it "nearly full", roughly 90%, or around 31Ah. The problem is that the Ohmmu batteries are typically ~150Ah capacity, so the Ford BMS routinely undercharges them -- the state of charge will drop to about 20% and that's where the truck will keep it, believing that the battery is "full".

Better logic in the 12V BMS would address the problem of 12V battery failure without having to go to exotic chemistries. The ideal solution would be for Ford to keep the DC-to-DC converter powered-up for longer when plugged in, even after the high-voltage battery was fully charged, to top off the 12V if and when needed.

I thought the Ohmmu had a plug-n-play replacement drop in for the Ford Lightning?

Yes reprogramming the BMS for the 12v would solve the problem - from one account I read somewhere, Tesla had the same issue with dying 12v batteries so the reprogrammed to keep the 12v topped off using the HVB.

If the truck would top off the 12v anytime the truck is plugged in to an L1 or L2 EVSE using grid power the way the battery is kept worm in winter, using the EVSE as a sort of trickle charger maintainer, that would be one solution.

Many of us have already rigged up an easy battery maintainer connection and keep our 12v on one in AGM mode any time the truck is sitting in the driveway...this is what I did based on what I saw others do:

I hook that SAE plug (on a 6 ft fused wire) to a NOCO Genius1 (with an SAE adapte). The other end of the fused wire has ring terminals on the 6mm battery bolts, the negative being downstream of the BMS sensor like this:

A simple $40 or so battery maintain is a cheap and easy solution.
I have had batteries last over 14 years on a battery maintainer.
All lead-acid batteries last longer when kept at 100% when not it use.
That's just a fact I learned my first year in engineering school many moons ago.

 

[dm5point0]

I also decided to go with the Ohmmu Sodium replacement as soon as I bought my truck. One, because of these stories and two, because I am adding a significant stereo and 12v Aux accessories (lights, Off-Road gear, etc.). I also will be keeping my Noco Jump box handy just in case.

Lead Acid is just old tech and from all my research...Sodium and Solid State batteries are where we are heading. Just watch the latest announcement from Donut Lab:



I am hoping that as my '25 Lightning ages, there will be an upgrade path to a sodium/solid state battery. Here's hoping

 

[El Duderino]

The simple 12v voltage devices the plug in the cigarette lighter work fine for monitor the battery state.

Forgive me, but I can't recall if this accessory port has un-switched (always hot) power going to it?

I like your idea of using the charger as a visual indicator of voltage level.

 

[dww]

The last straw for me was getting a false "Alarm triggered due to frunk" message in FordPass last night and coming out to a completely dead truck this morning. @Ford Motor Company ....

This is exactly what happened to me last weekend. Same frunk error from FordPass. 2023 Lariat, 29mo old battery by date stamp. Not even the key would open the truck. When we finally got the hood open the batter was reading 5V. No warranty if you don’t bring the truck in. How do you bring a truck in if the 12V won’t charge? I added a BT monitor to the new one and after seeing how the truck treats the 12V and how Chat says a 12V should be treated I’m going to be adding the SAE jumper to the charge port and install a battery tender above where I park to keep the 12V at the optimal float.

 

[fhteagle]

How do you bring a truck in if the 12V won’t charge?

The good news is it takes just a second or two of power from my little jump pack (or a second 12V battery) to wake the truck up enough that it can get to ready, even with a low voltage battery that's down around 6V. But it'll die as soon as you pull or insert the J1772 (why oh why does pulling the J1772 take the truck out of ready?!?!?), or use the power button to take the truck out of ready on purpose....

Ford gets an "F" for 12V system design to be sure.

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