Original owner of 22 lariat need help please

[Adventureboy]

12v lead acid batteries prefer to be at 100% for long life

While true for flooded lead acid batteries, not 100% true for AGM batteries. Most trickle chargers now have an AGM setting, which will charge the battery to near 100% SOC then drop the voltage to keep from burning the glass mats (Float). The good ones, like Noco, seem to land around 80% SOC for the AGMs. I've noticed, it pops into charge mode only momentarily about once per hour, then drops back down to Float voltage.

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[rugedraw]

I am the original poster .
I check my 12 volt battery with my Fantak charger and it at 95% charge . So that not it . I use the connect on the left side of frunk . Easy to remove the left frunk liner . I use as not able to disconnect and reconnect the battery because it looks more complicated to get to it . It looks like you have to remove the full frunk liner. This is more than I am comfortable with . Still stuck in the middle of the frunk update . Someone mentioned removing and reinstalling the modem breaker but which one and where . Still looking for help

Message me the VIN. I can check why the OTA is failing.

 

[rugedraw]

@Vegas Got your message. OTA hsitory for your truck is below. BCM OTA trigger was resent to you yesterday....right now it is sitting in the queue waiting for your truck to ping the server back to accept it.

If you look further down your OTA history, you have had several updates sent to you which have failed for various reasons. In some cases, it was due to the 12v battery being to low, and in othter cases, it was due to the truck just not pinging the server back to accept it. In the case of the failed BCM attempt in July, the error messages states the OTA packet was missing certain config in a

When you go to the screen where you check for updates and you check for updates, exactly what do you see on the touchscreen if you were to do that right now?

 

[chl]

While true for flooded lead acid batteries, not 100% true for AGM batteries. Most trickle chargers now have an AGM setting, which will charge the battery to near 100% SOC then drop the voltage to keep from burning the glass mats (Float). The good ones, like Noco, seem to land around 80% SOC for the AGMs. I've noticed, it pops into charge mode only momentarily about once per hour, then drops back down to Float voltage.

Interesting.

But I think that is wrong at least from everything I have read over the years, and recently - they prefer 100% just like all lead acid batteries and...if you only charge to say 80% eventually they will not charge past 80% and you lost 20% capacity.

At least that is what I have always heard...now if that's wrong, well, send me a link to a relliable source so I can learn something new...but...

See this:

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Never partially charge AGM batteries


When it comes to devices like smartphones and laptops, partial charge does not necessarily damage the batteries. This is because they use lithium batteries. In the case of AGM batteries, lead acid is what is used, and it reacts in a different way when partially charged. All Absorbent Glass Mat batteries have to be fully charged to 100% percent in order to maintain their capacity. When you partially charge AGM batteries, they with time lose their capability to charge to full capacity. If you constantly charge your AGM battery to only 60% for instance, it may eventually fail to charge past 60%. This, in turn, reduces the lifespan of the battery.


FROM: https://lifelinebatteries.com/blog/3-tips-that-will-increase-your-agm-battery-lifespan/
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If you have a source for that information you posted, I would like to check it out and see what they say...if what we have been told all these years is wrong the WOW!

 

[chl]

PS: that is a maker of AGM batteries liked above.

 

[Adventureboy]

Interesting.

But I think that is wrong at least from everything I have read over the years, and recently - they prefer 100% just like all lead acid batteries and...if you only charge to say 80% eventually they will not charge past 80% and you lost 20% capacity.

At least that is what I have always heard...now if that's wrong, well, send me a link to a relliable source so I can learn something new...but...

See this:

-----
Never partially charge AGM batteries


When it comes to devices like smartphones and laptops, partial charge does not necessarily damage the batteries. This is because they use lithium batteries. In the case of AGM batteries, lead acid is what is used, and it reacts in a different way when partially charged. All Absorbent Glass Mat batteries have to be fully charged to 100% percent in order to maintain their capacity. When you partially charge AGM batteries, they with time lose their capability to charge to full capacity. If you constantly charge your AGM battery to only 60% for instance, it may eventually fail to charge past 60%. This, in turn, reduces the lifespan of the battery.


FROM: https://lifelinebatteries.com/blog/3-tips-that-will-increase-your-agm-battery-lifespan/
-----

If you have a source for that information you posted, I would like to check it out and see what they say...if what we have been told all these years is wrong the WOW!

You are correct that it does need to charge to 100%, however, it doesn't hold it there like with a flooded battery. The modern chargers allow them to discharge a small amount and then top them back up so they aren't holding them on the high voltage for long periods of time like they do with the flooded batteries.
The first chart is the voltage at the battery with the NOCO attached - you can see it goes into charge mode about once per hour to top up to 100%. The second chart is an estimated SOC (accuracy isn't perfect on SOC since it is based only on voltage, so take it with a grain of salt but it is holding it between 85%-95% give or take a few percent). You can see the pattern that keeps the charger from burning the glass mats. Older AGM chargers held the float value above 13 volts, which shortened the life of the AGM batteries. The modern pulse charging that my NOCO does is safer.

 

[chl]

You are correct that it does need to charge to 100%, however, it doesn't hold it there like with a flooded battery. The modern chargers allow them to discharge a small amount and then top them back up so they aren't holding them on the high voltage for long periods of time like they do with the flooded batteries.
The first chart is the voltage at the battery with the NOCO attached - you can see it goes into charge mode about once per hour to top up to 100%. The second chart is an estimated SOC (accuracy isn't perfect on SOC since it is based only on voltage, so take it with a grain of salt but it is holding it between 85%-95% give or take a few percent). You can see the pattern that keeps the charger from burning the glass mats. Older AGM chargers held the float value above 13 volts, which shortened the life of the AGM batteries. The modern pulse charging that my NOCO does is safer.

Yes, I think that's where the confusion about what 100% charged is for an AGM.

A 12V AGM should be charged to a voltage of between 14 and 15 volts more or less, but then maintained at a lower voltage around 13.5 volts, the float voltage keeps it "full" without overcharging.

The 100% voltage is the 13.5 volts for an AGM, in my opinion anyway, and 100% "full" is where all lead acid battery are optimized for long life.

Note the exact voltages may differ between manufacturers these are 'ball park figures.'

The float voltage (full) is close to 90% of the charging voltage, which may be where the misunderstanding lay?

 

[Adventureboy]

lower voltage around 13.5 volts, the float voltage keeps it "full" without overcharging.

The 100% voltage is the 13.5 volts for an AGM, in my opinion anyway, and 100% "full" is where all lead acid battery are optimized for long life.

Agree for normal operating parameters, but not for trickle charging, where float voltages can be held for long periods of time - days, weeks, even months. Here is the science.

The float voltage on a flooded LA battery can be higher since this keeps the lead plates from sulphating and the extra energy/heat is burned off through water evaporation. You can replenish the water to make up for the evaporation. AGM doesn't have this option and is therefore more sensitive to higher float voltages for long periods of time.

100% SOC on an AGM is just below 13 volts (small variances by manufacturer, but say 12.9-13.0v is the most common). To be fair, it isn't an exact science since there is always a small draw on our Lightning AGMs pulling the voltage slightly down so they are never truly at rest unless you disconnect it from the truck. The actual 100% SOC under a normal standby load is probably just under 12.9v while not being charged. If you maintain a constant float voltage of 13.5 volts for an AGM battery, you will have a constant current going into a battery that is already at 100% SOC. This will eventually dry or burn the glass mats since the extra energy must go somewhere and it generates heat and evaporation causing the AGM to have a shorter life. 13.5v is ok when you are driving for an hour or two per day, but it can be on a battery maintainer for days, weeks, even months and that constant trickle overcharge will damage the glass mats over time. That's why good charger/maintainers pulse charge AGM near 100% SOC and let it drop a bit, so evaporation, drying, and burning is much more limited.

 

[chl]

Agree for normal operating parameters, but not for trickle charging, where float voltages can be held for long periods of time - days, weeks, even months. Here is the science.

The float voltage on a flooded LA battery can be higher since this keeps the lead plates from sulphating and the extra energy/heat is burned off through water evaporation. You can replenish the water to make up for the evaporation. AGM doesn't have this option and is therefore more sensitive to higher float voltages for long periods of time.

100% SOC on an AGM is just below 13 volts (small variances by manufacturer, but say 12.9-13.0v is the most common). To be fair, it isn't an exact science since there is always a small draw on our Lightning AGMs pulling the voltage slightly down so they are never truly at rest unless you disconnect it from the truck. The actual 100% SOC under a normal standby load is probably just under 12.9v while not being charged. If you maintain a constant float voltage of 13.5 volts for an AGM battery, you will have a constant current going into a battery that is already at 100% SOC. This will eventually dry or burn the glass mats since the extra energy must go somewhere and it generates heat and evaporation causing the AGM to have a shorter life. 13.5v is ok when you are driving for an hour or two per day, but it can be on a battery maintainer for days, weeks, even months and that constant trickle overcharge will damage the glass mats over time. That's why good charger/maintainers pulse charge AGM near 100% SOC and let it drop a bit, so evaporation, drying, and burning is much more limited.

Recommendations and opinions from manufacturers seem to vary from what you are saying.

But there is no point quibbling about what the best float voltage is. I just trust the manufacturers' recommendations which have been incorporated in the AGM profiles in a quality charger with an AGM setting to keep the battery at 100% in an optimum fashion.

I have seen information that says maintaining a steady float charge of 13.5 to 13,8 volts will not harm an AGM, from AGM manufacturers, and from well respected charger companies that make them with an AGM profile for optimum health, e.g., NOCO.

Yes, floating higher than that, some say above 14.3 volts, would be bad and could harm an AGM in the way you mentioned.

But another issue is sulfation that occurs when the voltage goes below the optimum float level of about 13.5 for too long.

Anyway, our Lightning are always using some energy from the battery, so having the AGM on a trickle charger to keep it floating at 13.5 volts is probably better than letting it fall too much due to these "parasitic loads," if one wants the battery to last longer, which I do. Since they aren't 'cheap' seems, prudent to me.

A smart charger made to handle AGMs is the best bet, they will use the optimum procedures to charge and maintain the battery.

I mean who is going to go out and check my AGM battery terminal voltage all the time to see where it's at?

I know that if I don't drive for a few days or just do short trips, the battery will fall too low for the OTAs (below 80-85%) because that happened to me the first year I had the truck. And going even lower, below 50%, is also bad for an AGM.

So a good quality trickle charger with an AGM profile is what I'd recommend, set it and forget it and presume the designers knew what they were doing and that it will lengthen the useful life of the battery.

Is there really any other way to go?

 

[MidAtlanticLightningClub]

I am the original poster .
I check my 12 volt battery with my Fantak charger and it at 95% charge . So that not it . I use the connect on the left side of frunk . Easy to remove the left frunk liner . I use as not able to disconnect and reconnect the battery because it looks more complicated to get to it . It looks like you have to remove the full frunk liner. This is more than I am comfortable with . Still stuck in the middle of the frunk update . Someone mentioned removing and reinstalling the modem breaker but which one and where . Still looking for help

What was the voltage of the 12v battery? 95% could mean lots of different things depending on your external charger.

 

[chl]

I am the original poster .
I check my 12 volt battery with my Fantak charger and it at 95% charge . So that not it . I use the connect on the left side of frunk . Easy to remove the left frunk liner . I use as not able to disconnect and reconnect the battery because it looks more complicated to get to it . It looks like you have to remove the full frunk liner. This is more than I am comfortable with . Still stuck in the middle of the frunk update . Someone mentioned removing and reinstalling the modem breaker but which one and where . Still looking for help

I'd guess, if it is NOT the battery, that the ATT cell service is weak or you have a problem with the communications electronics in your truck.

You could check the fuses first. Somewhere someone has a fuse diagram but I think it may be in the owners manual PDF.

I had the frunk update done at the dealership when I had a regular service check or maybe another update that required the dealer to install sometime last summer.

But then i also got it via an OTA on September 15th 2025, maybe a tweak to it, who knows, Ford is not the best at explaining the updates.

Go figure.

Running the wire for a battery charger was simply drilling a small hole in the plastic next to the hinge of the charge port cover and routing it to the battery compartment.

With the frunk open I could reach my arm down in there to find the hole and the wire and route it to the battery compartment in a place where nothing interfered with it (the frunk mechanism for example).

The 6mm screws on the battery had enough room for the metal ring connectors and a 6mm nut to hold them in place.

Need I say it? I will. Just be careful when tightening the POSITIVE side nut that your wrench does not touch the negative post or any part of the metal frame of the truck!

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