Bad 12V battery after 3 years

[GregScott]

Welp, it's only been 3 years and 37k miles, but ....i'm getting warnings about the vehicle turning off features to save battery life.
i know from past experience with gf's Ford Edge that it's a bad battery, but after only 3 years? that's a year or two early .
i'm not sure if it's going to last another month.
i have a month to decide if i'm buying out this lease or take the new 25' Lariat PB i have on order. i'd hate to drop $200 on a battery just to turn it in.

anyone else have a bad battery after 3 years?

Less than 1 year. Trans rebuild too. Probably my last Ford.

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[Snakebitten]

That battery under the back seat doesn't "prop up" the engine battery. It is auctioneered and supports certain key circuits in the memory and computer. So when its doing its thing it supplies a limited set of stuff.

That's not the way the factory service manual describes it.

The auxiliary battery is ALWAYS connected (parallel) to the main battery except during a "momentary bendix/flywheel start, or a BISG start. It is during those two "high amperage " events that the PCM opens the battery isolator and isolates the auxiliary battery and the electronic components from the High amperage output of the underhood AGM battery.

So 99.9% of the time, if you put a voltmeter on the AGM under the hood, you are getting a combined voltage reading of both 12V AGM batteries.

HammaMan can correct me if I'm wrong, since he is intentionally using his auxiliary battery to support a higher SOC of the underhood AGM. The strategy is fascinating, but he has to work out the nuances of using a different battery chemistry for the auxiliary battery.

 

[Sammyslab]

No worries. I stole this from one of @Kanuck's posts.

Thanks brother!

 

[Gros Ventre]

That's not the way the factory service manual describes it.

The auxiliary battery is ALWAYS connected (parallel) to the main battery except during a "momentary bendix/flywheel start, or a BISG start. It is during those two "high amperage " events that the PCM opens the battery isolator and isolates the auxiliary battery and the electronic components from the High amperage output of the underhood AGM battery.

So 99.9% of the time, if you put a voltmeter on the AGM under the hood, you are getting a combined voltage reading of both 12V AGM batteries.

HammaMan can correct me if I'm wrong, since he is intentionally using his auxiliary battery to support a higher SOC of the underhood AGM. The strategy is fascinating, but he has to work out the nuances of using a different battery chemistry for the auxiliary battery.

What you just described is an auctioneering implementation. It is a keep alive battery for certain and important circuits. So the manual can describe it as it will. The fact of electronics is that it is part of an auctioneering setup. The problem they are addressing is that when the 12VDC main battery is under the load of running the starter motor, its terminal voltage will drop to around 10.5VDC. That is an inherent characteristic of a battery and cannot be changed. So-o-o... Ford, in order to protect sensitive computing circuits that might "forget" things when voltage drops below a certain threshold, put in a battery that electronically takes over while the main battery is cranking the engine.

 

[Snakebitten]

What you just described is an auctioneering implementation. It is a keep alive battery for certain and important circuits. So the manual can describe it as it will. The fact of electronics is that it is part of an auctioneering setup. The problem they are addressing is that when the 12VDC main battery is under the load of running the starter motor, its terminal voltage will drop to around 10.5VDC. That is an inherent characteristic of a battery and cannot be changed. So-o-o... Ford, in order to protect sensitive computing circuits that might "forget" things when voltage drops below a certain threshold, put in a battery that electronically takes over while the main battery is cranking the engine.

OK. Fine. It's "auctioneering"

But your earlier quote of my post, and then your response, was to take issue with my claim that the auxiliary battery, and specifically in the experimentation of HammaMan, can "prop up" the voltage/SOC of the underhood AGM.

If the voltage of the auxiliary battery is higher than the underhood battery, regardless of the reason, then when they are connected in parallel, doesn't the auxiliary battery actually give current to underhood battery?

Or put another way, if you connect a battery (in parallel) that is at 13.4V to another battery that is at 12.3V, does the battery at 13.4 volts not automatically attempt to "charge" the battery that is at a lower voltage?

 

[v8440]

Yes, it will.

 

[Gros Ventre]

No, auctioneering doesn't work that way. Experiment any way you like. You;re just plain wrong. The smaller battery does not backfeed the main 12VDC battery. When its feeding something (ie its voltage is higher than the main 12vdc battery) it only feeds the key circuits intended. I had work done at my dealership that caused them to disconnect the main 12vdc battery in order to reset the memory. No reset occurred until they disconnected both batteries. The sole purpose of that smaller battery is to support key circuit voltages during the stater motor induced main battery voltage dip.

 

[scott011422]

No, auctioneering doesn't work that way. Experiment any way you like. You;re just plain wrong. The smaller battery does not backfeed the main 12VDC battery. When its feeding something (ie its voltage is higher than the main 12vdc battery) it only feeds the key circuits intended. I had work done at my dealership that caused them to disconnect the main 12vdc battery in order to reset the memory. No reset occurred until they disconnected both batteries. The sole purpose of that smaller battery is to support key circuit voltages during the stater motor induced main battery voltage dip.

The small battery can 100% backfeed into the main battery, They are connected together on the same terminal. No reset happened for you because both batteries are attached to the same terminal on the main underhood fuse block. Disconnect the main underhood battery and the aux is still powering the entire truck. Remove the ford battery isolator, and disconnect the main underhood battery and the truck will 100% try to crank up using the aux battery.

 

[Snakebitten]

Osmosis.

Electron version?

I could be just plain wrong, as you put it so elegantly ?. But if that isolator isn't isolating the underhood AGM from the the truck's 12V buss, which it isn't except for very few seconds at a time, well.............. dem der batteries are one battery bank. No?

I admit that I'm not an expert at any of this stuff, but most of this is just logical.

 

[Deleted member 22921]

Thanks brother!

It doesn’t work on my 2021 Lariat FX4. I tried this three separate times, unsuccessfully.

So I drove my truck to my local Ford dealership and informed them that I had replaced the previous Motorcraft H7 AGM battery with a new Everstart Platinum H8 AGM battery — and asked that they please perform a BMS reset for the new battery.

The Service writer replied that “No BMS reset is needed. Just drive the truck.”

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[riverdave]

2021/5.0/XLT... I also put in a Walmart H8 battery Sunday... did the reset just in case... went thru 2 H6 (replaced on warranty) since end of '21... did the tender thing, etc. and running fine now... I even wedge the H6 blanket around the H8 battery... mostly!

 

[Calson]

The Motorcraft battery in my 2022 F-150 failed and was replaced by the dealer in the first year. The second one was on its way to failing when I decided to replace it with a non-Motorcraft battery and to go with a H7 size battery.

Ford puts H6, H7, and H8 size batteries in its F-150 trucks. The XLT and lower priced trucks get the H6 battery regardless of how they are equipped. The bean counters decided that a H6 is good enough for Ford's less expensive truck (even when the MSRP is more than $50,000).

I now plug my truck into a battery maintainer when parked for a few days to insure that the battery will be able to start the truck. That was the best $50 I have spent on the truck. I wasted time and money believing that that the Ford battery management system actually worked.

 

[HammaMan]

But your earlier quote of my post, and then your response, was to take issue with my claim that the auxiliary battery, and specifically in the experimentation of HammaMan, can "prop up" the voltage/SOC of the underhood AGM.

Keep in mind he can't see my posts as he didn't like me telling him connecting a separate ground rod on its own, strictly for earthing the PB during structure power backfeed, was dumb. While I don't miss his posts in this browser's feed, I'm still waiting to hear about a nuisance trip from his misguided approach of wanting to earth the truck w/ its own rod.

The small battery can 100% backfeed into the main battery, They are connected together on the same terminal. No reset happened for you because both batteries are attached to the same terminal on the main underhood fuse block. Disconnect the main underhood battery and the aux is still powering the entire truck. Remove the ford battery isolator, and disconnect the main underhood battery and the truck will 100% try to crank up using the aux battery.

Yes and no -- It can't really crank as when it opens the isolator, the starting system is disconnected from the BCMC (under hood fuse/distribution box) -- both flywheel and OBISG starters are directly connected to the big AGM's posts. However it can start the ICE while in park as it uses the HVB/traction motor for that startup and doesn't open the isolator. It won't even know it's not there, though the power draw on systems up to that point could sag the voltage such that it tries to go for one of the 12v starters. The trick to avoid that would be to do the 2 step startup mode w/ sufficient HVB SOC and the truck won't know the big AGM is missing. Do beware though -- it won't be able to do any rolling starts w/out the the big AGM unless they've got a clutched-start mode baked in.

 

[scott011422]

Yes and no -- It can't really crank as when it opens the isolator, the starting system is disconnected from the BCMC (under hood fuse/distribution box) -- both flywheel and OBISG starters are directly connected to the big AGM's posts. However it can start the ICE while in park as it uses the HVB/traction motor for that startup and doesn't open the isolator. It won't even know it's not there, though the power draw on systems up to that point could sag the voltage such that it tries to go for one of the 12v starters. The trick to avoid that would be to do the 2 step startup mode.

Agreed, that's why I said if you removed the isolator.

100% on the rest of it. This really should be the prefered starting mode. I know there is a low limit for the HV battery. But they need to assign an even lower limit for starting. Doesn't take much to start the truck. under NORMAL operation there is prolly no reason the battery would ever get that low, Especially if there is a lower limit for starting only. Like the reserve tank on a dirtbike, just a lower fuel pickup in the same tank.

The big 12v underhood battery should just be a starting backup.

 

[HammaMan]

Yeah, the truck's HV SOC panic level is ~35%. Hit that and you need to heat up the battery to up its voltage and register a slightly higher SOC. Not sure why ford does that given that the 3-25% SOC range is where lithium chemistries can gobble up max current. It'd be one thing if the truck was still able to function while not charging the HVB, but it's dead in the water if the truck doesn't like its "low" SOC.
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