12 volt battery success ?

[chl]

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.

No it shuts off, might be a delay period.
And the manual says NOT to use it for trickle charging the battery (in essence - not exact wording).

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[chl]

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.

And when that low, the charge currents are high from the DC-DC converter (no apparent charge current restraints from what I've read anyway) which is another bad thing for the 12v 35ah AGM.

 

[chl]

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.

The 12v system is used for the J1772 L2 charging in at least two ways (my educated guesses):
to produce the J1772 signals, and
to close the HVB contactors and connect the HVB (if the truck is off).

So the 12v battery would be used for those if the truck is off.

If the truck is ON, the DC-DC converter should be providing 12v charging current to the 12v battery and the 12v system to perform those functions.

 

[djwildstar]

The 12v system is used for the J1772 L2 charging in at least two ways (my educated guesses):
to produce the J1772 signals, and to close the HVB contactors and connect the HVB (if the truck is off). So the 12v battery would be used for those if the truck is off. If the truck is ON, the DC-DC converter should be providing 12v charging current to the 12v battery and the 12v system to perform those functions.

This matches my experience with a marginal 12V battery.

If the truck is OFF, the 12V battery needs to be able to provide enough power to power-up the battery energy management system (BEMS) including signaling with the charger and closing the correct contractors to connect the high-voltage battery to either the on-board charger or to the DC charging pins on the CCS coupler.

One of the first problems I ran into with the marginal 12V battery is that the trutck would not initiate a charge when off: just before departure, when plugged into L2, it would not wake up and charge on schedule. During the trip, it failed to start DC fast charging when plugged into a charger but switched off.

Until I got the 12V replaced, I kept the truck running while plugging into both L2 and DC fast chargers. This did the trick -- charging started, even at the charger that failed when the truck was off.

 

[chl]

This matches my experience with a marginal 12V battery.

If the truck is OFF, the 12V battery needs to be able to provide enough power to power-up the battery energy management system (BEMS) including signaling with the charger and closing the correct contractors to connect the high-voltage battery to either the on-board charger or to the DC charging pins on the CCS coupler.

One of the first problems I ran into with the marginal 12V battery is that the trutck would not initiate a charge when off: just before departure, when plugged into L2, it would not wake up and charge on schedule. During the trip, it failed to start DC fast charging when plugged into a charger but switched off.

Until I got the 12V replaced, I kept the truck running while plugging into both L2 and DC fast chargers. This did the trick -- charging started, even at the charger that failed when the truck was off.

I decided a while ago that the only solution to avoid 12v battery issues was to keep it on a trickle charger maintainer when not using the truck.

A $40 or so charger is a lot less hassle than a dead or dying battery, even if the replacement is covered by the 3yr b-to-b warranty.

At least a few other owners came to the same conclusion.

Of course Ford could solve the problem with some programming changes to keep the 12v topped off (to 100%) all the time (apparently Tesla decided to do this for the same reason - dead 12v batteries).

But don;t hold your breath for that, alas.

 

[michael coffeen]

I waited until just past my 3 year B-T-B expired last August to evaluate and decided to replace my 12v LVB.

The Advanced Auto sales dude tested it, the results indicated it was still serviceable but I decided to err on the side of caution and replaced it with another H3 battery (Diehard)

Install of the new battery went fine in the store parking lot, no issues since the change.

What was the exact battery model?

 

[TaxmanHog]

What was the exact battery model?

https://shop.advanceautoparts.com/p...-60-minute-reserve-capacity-h3-xev/50001096-P

 

[djwildstar]

https://shop.advanceautoparts.com/p...-60-minute-reserve-capacity-h3-xev/50001096-P

This is the one I got, too.

 

[CRAIGC540]

I have an update pending and it will not proceed because LVB is low. I checked and it's at 55 so I guess it's time for a new battery, I've never had any problems and it will be 4 years old Feb 2026. I would like to get the DieHard EV Battery: H3 but the link given does not seem to ship to California. Can anyone link to where to get one in California or another battery to look into?
I left the truck on at work to see if the charge would go up and after 30 minutes it was at 59, I will check again in 1 more hour.


Edie..


After 6 hours leaving the truck on the LVB is at 70 percent.

 

[astrand1]

I have an update pending and it will not proceed because LVB is low. I checked and it's at 55 so I guess it's time for a new battery, I've never had any problems and it will be 4 years old Feb 2026. I would like to get the DieHard EV Battery: H3 but the link given does not seem to ship to California. Can anyone link to where to get one in California or another battery to look into?
I left the truck on at work to see if the charge would go up and after 30 minutes it was at 59, I will check again in 1 more hour.

If the programming is the same as the powerboost if you put the HVAC fan onto level 5 or higher it forces 14+ volts. I’m also unfortunately in Ca for work and was looking for a new battery. So I’ll be following this to see if there are some suggestions. Costco has a picture and listing for an H3 but they can’t find it in their system. Very odd. They have an H4 battery in stock but it looks to be about an 1.5 inches too big. So close though. lol.

 

[mr.Magoo]

Can anyone link to where to get one in California or another battery to look into?

https://www.google.com/search?q=h3+agm&newwindow=1

 

[CRAIGC540]

If the programming is the same as the powerboost if you put the HVAC fan onto level 5 or higher it forces 14+ volts. I’m also unfortunately in Ca for work and was looking for a new battery. So I’ll be following this to see if there are some suggestions. Costco has a picture and listing for an H3 but they can’t find it in their system. Very odd. They have an H4 battery in stock but it looks to be about an 1.5 inches too big. So close though. lol.

I was at Costco a few weeks back and the shop guys were out front selling batteries, they had a interstate H3 HGM BU battery for 149.00 at the time I was just wondering because I knew my battery was due soon. I think that I will get it from Costco. They at the time had to order it and would be there in 3 days.

 

[PJnc284]

This matches my experience with a marginal 12V battery.

If the truck is OFF, the 12V battery needs to be able to provide enough power to power-up the battery energy management system (BEMS) including signaling with the charger and closing the correct contractors to connect the high-voltage battery to either the on-board charger or to the DC charging pins on the CCS coupler.

One of the first problems I ran into with the marginal 12V battery is that the trutck would not initiate a charge when off: just before departure, when plugged into L2, it would not wake up and charge on schedule. During the trip, it failed to start DC fast charging when plugged into a charger but switched off.

Until I got the 12V replaced, I kept the truck running while plugging into both L2 and DC fast chargers. This did the trick -- charging started, even at the charger that failed when the truck was off.

Out of Spec ran into the same issue with a super low 12v on their Rivian R1S. They basically had to use jumper cables to an ICE car to get the contactors to close.

 

[CRAIGC540]

I just called Costco and they have the battery in the system with no way to order it so no Costco.

 

[astrand1]

I just called Costco and they have the battery in the system with no way to order it so no Costco.

That was the same for me. They pulled it right up but there was no stock and no way to order it. I even called interstate who they get their batteries from and they could not even pull it up they said they have never made an H3 AGM battery.

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