12V Battery FAQ

[dtbaker61]

Ok I guess what I'll have to do is look at the sticker on the battery after the dealership installs it?

you are over-thinking this.....

just let the Dealer install the new battery, although if the sticker shows it is more than a few months old you should ask for a note/letter to clarify the start date of the 36-mo warranty.

Regardless.... the easiest way to make sure the 12v is fully charged and de-sulfated is to leave your MME "on" for overnight/24-hrs. Just disable the "auto-off" setting, and leave it on overnight maybe once every 3 months

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[CzarR]

Hi, my 12v is dead so I ordered one from autozone, duralast agm h3. It has a manufacturing date of 06/2024. It reads 11v when the car is turned off and reads about 15v turned on @ 58% SOC. Is normal or better to return?

I also did a bms reset btw.

 

[Mach1E]

Hi, my 12v is dead so I ordered one from autozone, duralast agm h3. It has a manufacturing date of 06/2024. It reads 11v when the car is turned off and reads about 15v turned on @ 58% SOC. Is normal or better to return?

I also did a bms reset btw.

11v is dead. That battery is almost 2 years old. I would return and get a newer one for sure.

 

[Space_Pony]

Hi, my 12v is dead so I ordered one from autozone, duralast agm h3. It has a manufacturing date of 06/2024. It reads 11v when the car is turned off and reads about 15v turned on @ 58% SOC. Is normal or better to return?

I also did a bms reset btw.

How much did that battery cost? The last time I checked that battery cost considerably more than the Ford battery. It should be current stock at the price I saw.

 

[RickMachE]

Hi, my 12v is dead so I ordered one from autozone, duralast agm h3. It has a manufacturing date of 06/2024. It reads 11v when the car is turned off and reads about 15v turned on @ 58% SOC. Is normal or better to return?

I also did a bms reset btw.

I would never buy a battery dated 6/24. Nor one that read less than 12.6v before purchasing.

 

[Mach-Lee]

Hi, my 12v is dead so I ordered one from autozone, duralast agm h3. It has a manufacturing date of 06/2024. It reads 11v when the car is turned off and reads about 15v turned on @ 58% SOC. Is normal or better to return?

I also did a bms reset btw.

That is an old stock battery (20 months old). It should be charged 24-48 hours on a 12V battery charger before installation when it's that old to recondition it. Hence why I included that advice in case of a situation like this where you get an extremely old battery.

So if you can, take the battery out of the car, charge it for a day or two in your warm house, then put it back in. Or return it and get a newer one from a Ford dealer?

 

[CzarR]

How much did that battery cost? The last time I checked that battery cost considerably more than the Ford battery. It should be current stock at the price I saw.

$250. Returned it. I was hoping it is better quality vs oem.

That is an old stock battery (20 months old). It should be charged 24-48 hours on a 12V battery charger before installation when it's that old to recondition it. Hence why I included that advice in case of a situation like this where you get an extremely old battery.

So if you can, take the battery out of the car, charge it for a day or two in your warm house, then put it back in. Or return it and get a newer one from a Ford dealer?

Yup. Understood.

I returned it and bought one from O'Reilly Super Start Platinum. It had a manufacturing date of 12/25 only a month old and the rep tested it infront of me. I installed it and did a BMS reset twice today( accessory mode: 5 times high beam + 3 times brake + turn off open the door) even saw the battery blink like 3 times. I drove for an almost 1.5 hours battery soc only charged like 3%. It went from 64% to 67% Voltage is at 14.6V. Is it normal? I thought it charged faster than that.

 

[Space_Pony]

$250. Returned it. I was hoping it is better quality vs oem.

Yup. Understood.

I returned it and bought one from O'Reilly Super Start Platinum. It had a manufacturing date of 12/25 only a month old and the rep tested it infront of me. I installed it and did a BMS reset twice today( accessory mode: 5 times high beam + 3 times brake + turn off open the door) even saw the battery blink like 3 times. I drove for an almost 1.5 hours battery soc only charged like 3%. It went from 64% to 67% Voltage is at 14.6V. Is it normal? I thought it charged faster than that.

It looks like that battery costs about twice as much as a Ford battery, hope it's twice as good.

 

[Mach-Lee]

$250. Returned it. I was hoping it is better quality vs oem.

Yup. Understood.

I returned it and bought one from O'Reilly Super Start Platinum. It had a manufacturing date of 12/25 only a month old and the rep tested it infront of me. I installed it and did a BMS reset twice today( accessory mode: 5 times high beam + 3 times brake + turn off open the door) even saw the battery blink like 3 times. I drove for an almost 1.5 hours battery soc only charged like 3%. It went from 64% to 67% Voltage is at 14.6V. Is it normal? I thought it charged faster than that.

If you just reset the BMS the car needs to sit turned off and undisturbed for 8 hours to read the SoC accurately. Give it a couple days. Normal SoC should be around 65-90%.

 

[CzarR]

If you just reset the BMS the car needs to sit turned off and undisturbed for 8 hours to read the SoC accurately. Give it a couple days. Normal SoC should be around 65-90%.

Ohh. Understood. Thank you.

 

[waldo22]

If the vehicle can physically accept a larger H4 battery, I'm surprised someone hasn't found a forscan setting to make the change in vehicle configuration yet.

@Mach-Lee says it will accept an H4 AGM, and Gemini says that Forscan can update the BCM to tell the car it has a 50Ah LN1 (aka H4) AGM.

IMPORTANT: I have NOT verified these values yet. I will check with ForScan and report back. Don't just input random values from an AI LLM into your car until we can confirm these values are correct. This is just a starting point for more research.

The following is my condensed answer from Gemini:

1. Update Battery Capacity (Ah)

• Open FORScan and go to the Configuration and Programming tab (the wrench icon). Look for BdyCM (Main)—the non-As-Built version.
• Look for a parameter labeled Battery Target SoC or Battery Type/Capacity.
• In many Ford BdyCM modules, the 50Ah capacity corresponds to a specific battery type (often labeled as an LN1 50Ah AGM or similar). Select the option that closest matches your new 50Ah rating.
• If the text-based menu doesn't offer a 50Ah option, you would need to modify the hex values in the BdyCM (As-Built) at address 726-04-01.
  • Default is (H3 35Ah): The first two digits should be 30 (for the 35Ah AGM)
  • For a 50Ah AGM (Group H4 / LN1), change the first two digits to 35
  • Click "Write" on that specific line. FORScan will warn you about a checksum error; click "Yes" to allow it to calculate the new checksum automatically.

2. Reset the BMS
Even if you change the capacity, the car still thinks it’s attached to an old, "tired" battery. You must reset the BMS so the car starts its learning process from 100% health. You can do this via FORScan or a manual sequence:

Using FORScan:

1. Go to the Service Functions tab (the wrench icon).
2. Select BMS Reset (Battery Monitoring System Reset).
3. Follow the prompts (Ignition ON, Engine/Motor OFF).

Manual Method (No laptop required):

1. Get in, close the door, and put the car in Accessory Mode (Start button ON, foot OFF the brake).
2. Flash High Beams 5 times.
3. Press and release the Brake Pedal 3 times.
4. Wait ~10 seconds. The red battery icon on the dash should flash 3 times, confirming the reset was successful.

3. The "Sleep" Period
After the reset, Ford recommends letting the car sit undisturbed (locked, with no charging) for at least 8 hours. During this time, the BMS measures the "rest voltage" of the new battery to calibrate the high and low points of its SoC curve.

 

[dtbaker61]

Hi, my 12v is dead so I ordered one from autozone, duralast agm h3. It has a manufacturing date of 06/2024. It reads 11v when the car is turned off and reads about 15v turned on @ 58% SOC. Is normal or better to return?

I also did a bms reset btw.

return it and get a fresh one from ford dealership

 

[Mach-Lee]

@Mach-Lee says it will accept an H4 AGM, and Gemini says that Forscan can update the BCM to tell the car it has a 50Ah LN1 (aka H4) AGM.

1. Update Battery Capacity (Ah)

• Open FORScan and go to the Configuration and Programming tab (the wrench icon). Look for BdyCM (Main)—the non-As-Built version.
• Look for a parameter labeled Battery Target SoC or Battery Type/Capacity.
• In many Ford BdyCM modules, the 50Ah capacity corresponds to a specific battery type (often labeled as an LN1 50Ah AGM or similar). Select the option that closest matches your new 50Ah rating.
• If the text-based menu doesn't offer a 50Ah option, you would need to modify the hex values in the BdyCM (As-Built) at address 726-04-01.
  • Default is (H3 35Ah): The first two digits should be 30 (for the 35Ah AGM)
  • For a 50Ah AGM (Group H4 / LN1), change the first two digits to 35
  • Click "Write" on that specific line. FORScan will warn you about a checksum error; click "Yes" to allow it to calculate the new checksum automatically.

2. Reset the BMS
Even if you change the capacity, the car still thinks it’s attached to an old, "tired" battery. You must reset the BMS so the car starts its learning process from 100% health. You can do this via FORScan or a manual sequence:

Using FORScan:

1. Go to the Service Functions tab (the wrench icon).
2. Select BMS Reset (Battery Monitoring System Reset).
3. Follow the prompts (Ignition ON, Engine/Motor OFF).

Manual Method (No laptop required):

1. Get in, close the door, and put the car in Accessory Mode (Start button ON, foot OFF the brake).
2. Flash High Beams 5 times.
3. Press and release the Brake Pedal 3 times.
4. Wait ~10 seconds. The red battery icon on the dash should flash 3 times, confirming the reset was successful.

3. The "Sleep" Period
After the reset, Ford recommends letting the car sit undisturbed (locked, with no charging) for at least 8 hours. During this time, the BMS measures the "rest voltage" of the new battery to calibrate the high and low points of its SoC curve.


IMPORTANT: I have NOT verified this yet. I will check with ForScan and report back.

You have no idea if that's the correct address, the AI is just guessing and probably pulling data from another forum. As you can see, FORScan doesn't know the correct battery type either since the factory battery is 35 Ah not 60 Ah.

 

[MachE70]

Bad New 12V?
The 47-month old 12V battery in my '22 GT has never given me any problems, but I just received the 12V warning in FordPass and decided to replace the battery. After a trip to the dealer and $292, the new battery measured at 12.08V when I brought it home. I immediately put my AGM charger on it for 7-8 hours which raised the voltage to 12.87. The car then sat for 2.5 days in my garage, and the voltage had dropped to 12.16. Over the last several days of low mileage errands and overnight HVB charging, the voltage has typically been around 12.35 several hours after driving. This morning after an overnight rest, the voltage was 12.10. Is this battery salvageable, or should I demand a new replacement from the dealer?

 

[waldo22]

You have no idea if that's the correct address, the AI is just guessing and probably pulling data from another forum. As you can see, FORScan doesn't know the correct battery type either since the factory battery is 35 Ah not 60 Ah.

I did say:

IMPORTANT: I have NOT verified this yet. I will check with ForScan and report back.

I will move that to the top of my post.

I am as wary of AI answers as you are. I did verify with the CyanLabs database that `726-04-01` is the correct address for the BMS settings for other Fords, like the F-150 and similar. The actual correct address for our Mach-e is 726-02-01 (for battery type) and 726-02-04 (for Target SoC).

However, I have NOT verified that Gemini is correct about the hex values to change.

Gemini says that the first 2 hex digits are not an Ah value in hex, but rather point to the index in a lookup table of battery types. It also says the default setting is 30, whereas you can clearly see that it is set to 33 in your ForScan screenshot.

Gemini also says that the 1st 2 digits (hexits?) of the last block of `726-04-01` are the target SoC of the 12V battery in hex, with the default value being `50` (in hex which is 80% in decimal), and to change it to `5A` or `5F` for 90% or 95% SoC, respectively. However, you can clearly see in your screenshot that those 2 digits are `4B`, which is at least plausible at 75%, but there is no way to verify that yet.

The upshot is that more research is required before setting values from an LLM in your car, but this is a good starting point for that research.

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