Answers to "When does my LVB get charged" (with graph)

[TechnoSwiss]

I've seen the question a lot about when the LVB battery gets charged, and a lot of answers, some good, some not quite correct. I haven't seen one yet with any direct evidence. I thought I'd share one with a graph showing voltage on the LVB.

I have a BLE battery monitor on all of my cars, with data-logging, and dump that data to my server at home when the Lightning is in the driveway. Yesterday managed to hit most of the conditions for LVB charging, as you can see labeled above.

While driving the peak voltage is around 14.7V (testing with my Fluke DMM this battery monitor is within +/-0.2V) with a peak at 15V.

You can see a lot of ups and downs on the goodie drop-off trip, where while parked and knocking on doors (truck left on because it was cold), and we drop down to 13V.

Moving on to charging overnight, and the LVB gets a boost at 14V.

In the morning I manually turned on the climate control to knock the frost off the windows before running to the Post Office, and you can see we're back up to 14.7V while warming the truck up, and then repeat the 14.7V while driving, 13V while parked at the post office.

Downloading and collecting data is done via a Raspberry Pi, BLE dongle with external antenna, and python scripts because on this GitHub repo https://github.com/KrystianD/bm2-battery-monitor for anybody interested.

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[RickLightning]

What this doesn't clearly show is:

- 12v not being charged when the vehicle is done charging, but still plugged in.
- 12v dropped in charge as truck sits unused, until it reaches a level, where the HVB kicks in the charging again.

 

[TechnoSwiss]

This is the longest I've ever had the truck just sitting and the only time I've seen the LVB dip below 12.5V in almost year I've owned it. The lowest drop there is 12.1V right after a short drive. The peaks around 11/28 are a few short trips to and from friends homes for Thanksgiving dinner, and leftovers. That small plateau on 11/30 appears to be the system running a charge cycle on the LVB after finishing charging the HVB (but system is still on-plug)

 

[htobin]

I am pretty much non-technical. I started getting messages about my battery and when I tried to check it my self, it tested OK. However when I brought it to the dealer it was pretty much shot. It was replaced under warranty and no further message. I have a 2023 lariat with 30,000 miles.

 

[F150guy]

Thanks for sharing. You have some very interesting data views in this.

Given the LVB loses some state of charge while sitting over the course of a week or more, why not just start climate for 15 minutes in the middle of that week so the HVB will top up the LVB? And it would have hardly any impact to the HVB level. Then the LVB will be closer to a healthier state of charge for the week. Would this maybe eek out more overall life for the LVB??

I charge my boat batteries on trickle during winter to keep them at a higher SOC for long term health and life.

 

[Maquis]

Thanks for sharing. You have some very interesting data views in this.

Given the LVB loses some state of charge while sitting over the course of a week or more, why not just start climate for 15 minutes in the middle of that week so the HVB will top up the LVB? And it would have hardly any impact to the HVB level. Then the LVB will be closer to a healthier state of charge for the week. Would this maybe eek out more overall life for the LVB??

I charge my boat batteries on trickle during winter to keep them at a higher SOC for long term health and life.

No need to do that. If the 12V gets low enough, the truck will charge it. You only get 2 remote starts in between drives.

 

[F150guy]

No need to do that. If the 12V gets low enough, the truck will charge it. You only get 2 remote starts in between drives.

I must have forgotten the 2 remote starts. But, my goal was to keep the SOC as high as possible. Isn't that better than letting Ford letting it get lower before the HVB starts charging?

 

[mr.Magoo]

I've seen the question a lot about when the LVB battery gets charged, and a lot of answers, some good, some not quite correct. I haven't seen one yet with any direct evidence. I thought I'd share one with a graph showing voltage on the LVB.

More data is always welcome, but it's pretty well known that the battery is charged / maintained when the truck is on ? (ie. driving, charging or running climate control)

There's also a document from Ford that shows the conditions where it would charge the LVB when the truck is OFF (Pages 4-6):
https://www.f150lightningforum.com/...–-w-12v-battery-power-and-ground-points.7461/

There's "evidence" that corroborates this, here:
https://www.f150lightningforum.com/...ry-mode-vs-starting-vehicle.18086/post-363649
https://www.f150lightningforum.com/...ry-mode-vs-starting-vehicle.18086/post-363717


The only time that I've seen the "protection" mechanism fail is when I left it the truck in Neutral, thinking things / the truck, would put itself back in park when shutting off and it didn't:
https://www.f150lightningforum.com/...h-the-truck-off-it-will-drain-your-lvb.24876/

 

[PrimeRisk]

No need to do that. If the 12V gets low enough, the truck will charge it. You only get 2 remote starts in between drives.

That doesn't seem to work very well. My Lighting is not my daily driver. I drive it on the weekends when I do truck things, so it commonly sits all week without being driven. If I don't have the LVB on the smart charger and happen not to use it on a particular weekend, I will get LVB warnings. I just plug it in on Sunday nights and don't unplug it again until I drive it again. Since I've done this I haven't gotten a single LVB warning and my constant communications lockups have disappeared.

The truck doesn't seem to manage the LVB well by itself at all.

 

[chl]

I've seen the question a lot about when the LVB battery gets charged, and a lot of answers, some good, some not quite correct. I haven't seen one yet with any direct evidence. I thought I'd share one with a graph showing voltage on the LVB.

I have a BLE battery monitor on all of my cars, with data-logging, and dump that data to my server at home when the Lightning is in the driveway. Yesterday managed to hit most of the conditions for LVB charging, as you can see labeled above.

While driving the peak voltage is around 14.7V (testing with my Fluke DMM this battery monitor is within +/-0.2V) with a peak at 15V.

You can see a lot of ups and downs on the goodie drop-off trip, where while parked and knocking on doors (truck left on because it was cold), and we drop down to 13V.

Moving on to charging overnight, and the LVB gets a boost at 14V.

In the morning I manually turned on the climate control to knock the frost off the windows before running to the Post Office, and you can see we're back up to 14.7V while warming the truck up, and then repeat the 14.7V while driving, 13V while parked at the post office.

Downloading and collecting data is done via a Raspberry Pi, BLE dongle with external antenna, and python scripts because on this GitHub repo https://github.com/KrystianD/bm2-battery-monitor for anybody interested.

Thanks for sharing the data.

It looks like your battery is healthy and staying within normal ranges, never went above 15 or below 11.6.

I assume your truck and battery are relatively young (a 2024) and you say you have owned it for almost a year.

There have been quite a few 12V battery failures and warranty replacements in earlier model years, and we had some battery management system changes that may have helped keep the 12v battery in better health and at an SOC where OTAs can be installed. That was an issue with the Mach-e as well.

Plenty of threads about the failed or failing 12v batteries and the symptoms observed on this and other forums. There have been some about the BMS sensor and other 12v battery related components having failed and needing replacement. Rodents chewing the wiring has also been an issue.

Other post data has shown periodic high charging currents, above what would be optimum for a 35Ah battery (10.5A or so) which as a fellow EE you know can be detrimental to the battery.

The programming originally would let the battery get discharged below 50% for up to 48hrs before initiating a charge cycle, also not great for AGM batteries, but that has been modified.

That said, any 12v vehicle battery can benefit from being kept at 100% as much as possible for longevity, so many of us have put ours on AGM mode trickle chargers whenever possible.

Some of us, like myself, don't drive our trucks every day, and a trickle charger gives us a bit of insurance that our 12v batteries will remain healthy.

Keep us posted if anything anomalous shows up in your 12v charging system.

 

[chl]

PS: for a not too technical post about when the 12v battery gets charged see this post from the Mach-e forum:

https://www.macheforum.com/site/threads/how-to-get-failed-otas-to-install.29749/

 

[tearitupsports]

On your graph from about 8:15pm to 6:45am the next day, was the truck actively charging (energy being put into the battery) or just sitting with the charger plugged in.
I suspect it finished charging at the 6:45 time frame, which matches all my previous data.

One reason I set my charge station to charge slower (40A instead of 80A) is that it helps to charge the LV battery better due to the more time charging.

 

[topher10]

I am also curious about maintaining the 12V. I was out of town for a week-long trip, with the truck off plug at 50% battery. I got home and drove it around the corner (less than 1/4 mile) to the store. Coming out of the store, I popped the frunk, and it failed to operate correctly. The truck gave all sorts of warnings/errors and would not turn on. Walked home, brought back another car, and jumped it, and it worked with no trouble. I am now very cautious with the 12V after letting the truck sit for any length of time. I either drive it and leave it on while running errands, or I plug it in before driving it.

 

[chl]

I am also curious about maintaining the 12V. I was out of town for a week-long trip, with the truck off plug at 50% battery. I got home and drove it around the corner (less than 1/4 mile) to the store. Coming out of the store, I popped the frunk, and it failed to operate correctly. The truck gave all sorts of warnings/errors and would not turn on. Walked home, brought back another car, and jumped it, and it worked with no trouble. I am now very cautious with the 12V after letting the truck sit for any length of time. I either drive it and leave it on while running errands, or I plug it in before driving it.

Like some other folks around here, I put my 2023 Pro on a trickle charger (NOCO GENIUS1) in the AGM mode every day. I rigged up an SAE cord inside the charge port to make it more convenient and not have to leave the frunk open.

Am going to run an extension cable to my garage so I can keep the charger indoors, for now it is in a battery bag I used for LiPo's sitting on the front tire out of the weather:

That's a make-shift weather cover for the charge port area (plastic bag and a couple of long twist ties) and it has held up through snow sleet and rain - not pretty to look at but does the job.

To run the wire I reached in through the top of the frunk under the lift strut when opened to determine where to drill a small hole next to the hinge of the charge port door. I made a hole just big enough for the wire with an SAE plug on the end.

It was a spare wire I had from another charger, and after I got it over to the battery area, I spliced it to a fused wire with ring terminals that would fit the 6mm bolts on the battery positive and the negative DOWNSTREAM of the BMS!

Have to be down stream of the BMS or else the system will not know the battery has been charged (the black wire on the left of the picture).

Other owners have done similar modifications.

Of course be careful to avoid sparks and shorts whenever connecting anything around the battery, and wear protective eye wear and gloves just in case.

 

[Maquis]

That doesn't seem to work very well. My Lighting is not my daily driver. I drive it on the weekends when I do truck things, so it commonly sits all week without being driven. If I don't have the LVB on the smart charger and happen not to use it on a particular weekend, I will get LVB warnings. I just plug it in on Sunday nights and don't unplug it again until I drive it again. Since I've done this I haven't gotten a single LVB warning and my constant communications lockups have disappeared.

The truck doesn't seem to manage the LVB well by itself at all.

Mine sits a lot as well. Less than 15K in 3 years. Routinely sits for a week or more. I’ve never gotten a warning.
Interesting side note - after a few days (never bothered to count the exact number), I notice that the interior lights fail to come on when I open the door. Some of the modules must be shutting completely down to conserve battery. I don’t think it’s a full deep sleep, though.

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