Why isn't the 12v battery always charged?

[queuewho]

but there are many times I go into my truck without wanting it to turn on. Don't take that away!

I will say I agree there, it was super annoying that the climate system immediately came on any time I opened a door on my model 3. I'd intentionally turn it off if before getting out in the summer if I knew I might be in and out of the car later. It may have been a big contributor to the hvac system always getting a smell... running the AC for like, 20 seconds and then having condensate pool up inside it all the time... But, having it fire up without AC/Heat should be fine, so it could check the battery volts and charge it if necessary.

I assume in a tesla every time the contactors were engaged, the DC-DC converter began powering the car instead of the 12v battery. There's probably a bit of high voltage drain because of their decision, but I never noticed it to be an issue in 4 years.

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[RonTCat]

I have zero expertise in FDRS. My understanding is that the OTA technology is A/B. It downloads a module update to A, with B being the old software. Then it swaps it to run A. If there is a failure, B kicks back in.

No OTA update takes hours. Many take 2 minutes. Some take longer, that's why Ford has you set the schedule to apply them when you're not using the vehicle, like 1AM. Mach-Es just got the GUI update in the past 2 weeks and it was no different than past updates as far as impact on the vehicle.

You can look in Wikipedia at the list of OTA updates. My 2022, acquired in May, has received around 15 updates.

https://en.wikipedia.org/wiki/Ford_Power-Up_Version_History

Not all modules are A/B, some are still erase and replace.

 

[mr.Magoo]

https://www.f150lightningforum.com/...–-w-12v-battery-power-and-ground-points.7461/

Check out the PDF in this post and page 6 in particular, it lists the conditions where the onboard DC/DC ( HVB to LVB) charger kicks in.

 

[MM in SouthTX]

Would it be a problem to put in a larger deep cycle battery in place of the OEM battery?

 

[Leroyjac75]

No, as far as we know, this has always been working. the challenge is that the level needed for an update may be higher than the level to trigger a recharge.

It is also suspected that the level to trigger a recharge is lower if the vehicle is off, than if it is one, which is why going for a drive can trigger the charge cycle and get the 12V charge high enough for the update.

As to why the update doesn't start by triggering the charge cycle, I have no idea. I suspect we are seeing a lot of legacy ICE assumptions baked into the 12V charging scheme.

All one has to do is place a voltage meter on your 12v accessory port.I doubt the system allows the 12v voltage to sit below 12.2 voltas or so… my i3 rests at approx 12.5 volts on its 19aH battery. The Lightning seems to have more accessory activity so I expect it cycles a charge mode more often. I would be suspect of the battery if it is reaching a low state.

 

[queuewho]

https://www.f150lightningforum.com/forum/threads/f-150-lightning-electrical-system-overview-–-w-12v-battery-power-and-ground-points.7461/

Check out the PDF in this post and page 6 in particular, it lists the conditions where the onboard DC/DC ( HVB to LVB) charger kicks in.

Some good info here, seems like OTA updates should interrupt the normal automatic 48 hour 12v check/charge and force it to charge up the 12v battery. It also seems that an extremely low battery will also interrupt that check and force a top-off as well.

That being said, what's with all the typos?

 

[chl]

My 2012 Leaf 12volt battery does not charge via the Li battery, so when I was a away for about a month in winter, and I had the charge timer on, AND the Leaf was connected to the EVSE (as recommended by the Nissan salesman) at some point the 12v battery went dead, or at least so low the Leaf would not start. I had to jump it from my Ford Ranger. Since then, I keep the 12v on a trickle charger. It does seem strange that the geniuses who design these things didn't think to keep the 12 volt battery topped off using the Li battery stored energy - go figure.
At some point in the 11 years I've had the Leaf I had to replace the 12v battery. My 2001 Ford Ranger battery lasted me over 15 years - but then it doesn't have all the energy vampires that the Leaf has, just the FOB signal is powered when it's off, no charge timer and telemetrics like the Leaf has.

 

[mr.Magoo]

Thought you might find this interesting, it's from a logging session I did this morning with the vehicle turned off.

Couple of things worth noting...
1. When plugged in / charging, the 12V battery is "trickle charged" by the DC/DC converter
and all load on the 12V system is coming from the DC/DC converter rather than the battery.
At the first point I stopped the charging from my phone, plug still in the car and at that point the DC/DC converter is also disabled. (not sure if this is also the case if the set charge limit is reached or only if/when you stop the charge completely)

2. Even a short dip in voltage (orange line) will trigger a "Deep sleep" message. In my case it was twice in a 5min window (I only log every minute). So the warnings people get can be false positives.

3. Once mine got under 40% SoC the onboard DC/DC converter kicked in, charged the battery to 87% and then shut off again.

4. The current draw on a vehicle that's supposedly turned off is quite high (bounces between 4-6A) Granted - I'm scanning the OBD every minute and I'm not sure what that does in terms of not letting modules go to sleep, so I'm not sure if 4-6A is normal for a vehicle that's shut off (I'll verify that later) But, if it is, that means that the 35Ah battery we got will last just about as long as you can see in the graph below (6hrs between "fill-ups") if this is normal, it means the battery will go through 3-4 drain / recharge cycles per day.

5. If this is "normal" then what is the expected life of the 12V battery ?
AGM batteries have relatively short lifespan (from what I can read up on), the deeper the discharge the shorter the life. According to some sources if you discharge to 40% (like in my case) you can expect around 800-900 cycles. 900/4 = 225 days or 7-8 Months life expectancy.
Granted, it all depends, if you drive a lot and charge a lot (so that the 12V is handled by the charger / DC/DC converter most of the time) you'll get a lot more. But if you, like my self, don't drive that much the 12V battery might be a thing you'll have to change every year.

 

[srspring551]

Time to connect a trickle solar charger to my 12V battery and leave the panel on my dash like I used to do with my older vehicles a long time ago!

If Page 182 of the 2023 manual says:

Do not plug in any device that supplies power to the vehicle through the power points.

Does that mean we should NOT use this? Have you used it?

 

[hturnerfamily]

My 2012 Leaf 12volt battery ... at some point the 12v battery went dead, or at least so low the Leaf would not start. I had to jump it from my Ford Ranger.

Sounds like my purchase of my used 2014 Leaf back in 2020... I arrived and the owner immediately told me the bad 'news'... the car won't turn ON, much less drive... I had driven quite a ways to get to the car, with a good negotiated price already in place, so I wasn't about to 'give up' that easily - although the owner had. He didn't realize what I already knew: the 12v battery is suspect, NOT the huge drive battery, which many owners might mistakenly believe is the 'problem'.
I jumped the LEAF easily with my 2014 Ford Focus. The Leaf then turned ON. The Leaf, though, still would not go into DRIVE. Time for a new battery. She then purred like a kitten. I drove her 20,000 miles, then sold her, several years later, for MORE than I bought her for. Sweet.

 

[mr.Magoo]

Thought you might find this interesting, it's from a logging session I did this morning with the vehicle turned off.

I noticed something really interesting / concerning this morning after running another "all-nighter".
This time the onboard DCDC charger kicked in around 3am and @ 40% SoC on the LVB (as it should).

But then 3hrs later when the battery, for the 2nd time, reached 40% the onboard charger never kicked in !?
If I understand it correctly the 40% is somewhat conditional and subject to a 48hr "grace period" where it may or may not kick in, but supposedly, at 30% it's an unconditional charge/activation of the DCDC charger.

Well, as you can see, in my case it never activated again.
I let it go as low as 15% before I "chickened out" and started the truck and that's when the onboard DCDC charger started as well (around 8am).

In the past (it was a few software updates ago) it would do the 40% re-charge several times in a row, so it's a bit concerning to see that even a super low (15%) SoC won't trigger the onboard DCDC charger.

T

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