Why isn't the 12v battery always charged?

[chl]

Owners manual describes this very thing happening. "Prolonged use of this mode can cause the 12v battery to run out of charge"

Yes it does.

It just doesn't tell the whole story, about the details, some of which are unexpected.

Like if the truck is OFF, it is still using a heavy 12V load in temp neutral mode and will drain the LVB because the HVB to LVB is disabled.

And that the fail-safe HVB to LVB transfer at below 30% won't happen during the time the truck is OFF and in temp neutral mode.

It also does not say that if the truck is in temp neutral mode but is ON, the 12v battery will be kept charged and not drained, which seems to be the case.

But now we know.

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[RLXXI]

Yes it does.

It just doesn't tell the whole story, about the details, some of which are unexpected.

Like if the truck is OFF, it is still using a heavy 12V load in temp neutral mode and will drain the LVB because the HVB to LVB is disabled.

And that the fail-safe HVB to LVB transfer at below 30% won't happen during the time the truck is OFF and in temp neutral mode.

It also does not say that if the truck is in temp neutral mode but is ON, the 12v battery will be kept charged and not drained, which seems to be the case.

But now we know.

I use bluetooth battery monitors on a lot of equipment. Batteries are already a crap shoot, every little bit helps.

 

[chl]

I use bluetooth battery monitors on a lot of equipment. Batteries are already a crap shoot, every little bit helps.

Since getting smart battery maintaining AGM mode trickle chargers for my vehicles I have not had any problems, but time will tell with the Lightning, too early to say.

Nothing lasts forever, except on the Internet, lol.

 

[andres1227]

Perhaps this situation has changed, or the system wasn't working for some folks? I just found the following on page 443 of the 2023 manual:

If the 12 volt battery level is low, the high voltage battery transfers energy to the 12 volt battery when the vehicle is off.

I can second this! I am outside the country and I got a message in the app the other day saying that I had 83% and 0 miles. The charging screen said: “low battery, charge soon”. As I am 3000+ miles away from home and since I did not leave my truck connected, I decided to not worry about it and deal with it back home. Two days later, everything went back to normal and it has been like that since then.

 

[chl]

I can second this! I am outside the country and I got a message in the app the other day saying that I had 83% and 0 miles. The charging screen said: “low battery, charge soon”. As I am 3000+ miles away from home and since I did not leave my truck connected, I decided to not worry about it and deal with it back home. Two days later, everything went back to normal and it has been like that since then.

Yes, the devil is in the details, the system lets the 12v battery go down to 40% for 48 hours then kicks in to add charge, but according to some posts, not to 100%.

If the charge level goes down to 30% then it initiates the energy transfer without waiting.

It is not the best way to ensure battery longevity however.

The charging logic is detailed in the attached, although I think they changed it a bit after publication because so many batteries were being replaced under 3 year waranty.

 

[andres1227]

Yes, the devil is in the details, the system lets the 12v battery go down to 40% for 48 hours then kicks in to add charge, but according to some posts, not to 100%.

If the charge level goes down to 30% then it initiates the energy transfer without waiting.

It is not the best way to ensure battery longevity however.

The charging logic is detailed in the attached, although I think they changed it a bit after publication because so many batteries were being replaced under 3 year waranty.

Great info. Thank you!

 

[mr.Magoo]

I can second this! I am outside the country and I got a message in the app the other day saying that I had 83% and 0 miles.

So, I'm guessing that was in reference to the main (hvb) battery.
Generally speaking the only "error" message you get for the 12V system is a warning that accessories might be causing drain, that message occurs when the 12V is drained below 40% and the "energy transfer" (the truck wakes up to charge the 12v battery) occurs.

 

[chl]

So, I'm guessing that was in reference to the main (hvb) battery.
Generally speaking the only "error" message you get for the 12V system is a warning that accessories might be causing drain, that message occurs when the 12V is drained below 40% and the "energy transfer" (the truck wakes up to charge the 12v battery) occurs.

The message seems odd: "83% and 0 miles" so I thought maybe it is a glitch because of a low 12V battery?

But I think other folks got a similar message after the update to something or other, maybe the app when it added the PPOB back in?

It's all a blur now...

 

[chl]

Great info. Thank you!

This 12v battery issue has been around for some time and I have accumulated a bunch of info that is sometimes useful, like that doc that someone else posted in 2023 or earlier?

But I believe the algorithm was changed somewhat to keep the battery healthier.

I recently read how Tesla was having too many dead 12v batteries for similar reasons and changed their algorithms to keep the 12v topped off to 100% on a regular basis - from a post so I haven't got any direct knowledge about that.

Ford could do the same if they were on the ball...alas.

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