Is there a meter or method to determine the 12volt battery state of charge (SOC)?

[Superdaddy]

Yesterday I towed my travel trailer about 75 miles, parked to register in the office and came out to "Stop Safely". Well it was already stopped so I followed many suggestions listed here:
1) disconnect for two minutes then reconnect, fail.
2) disconnect for five minutes then reconnect, fail.
3) jump start, not sure if that was a suggestion but it also failed.
4) charge the battery, tried to start after battery charger indicated charge complete, fail.
5) wait three hours and try again, it started.

I took it to the campsite, got up and it started so I came home. I couldn't find a replacement cheaper than Ford ($189) so I drove down to the dealer and the service writer (I asked how much installation was), looked up the SOC for yesterday it was at 27% and just before I left the house it was 45%. This he saw this from my VIN number on his computer. He said they need to diagnose the problem (about $365) and if it is truly only the battery install it would be $285 plus the battery because they had to reprogram a module. I asked if I bought the battery and put it in then how much was it to reprogram the module, he said still $285. If I bring it in Monday morning it would be ready Tuesday afternoon. I made the appointment but I will call another dealer in the morning to inquire about the reprograming fee.

So all that got me wondering how can I see the SOC of the 12 volt battery, I see no menu option to get this information.

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[GoodSam]

how can I see the SOC of the 12 volt battery,

Please search the forum for 12V or LVB state of charge (SOC) and you will find many using a OBD bluetooth device to plug into that port and then the CarScanner app on the smartphone can be used to find that parameter and more. Avoid the dealer!
If you have been using the original 12V battery since 2022, most folks seem to have to change it out by 3 years of use due to Ford not maintaining the charge level like they could at 100% always to extend the life of the lead acid battery.

If you put in a new LV battery, its battery management system? BMS module on the Negative post can be easily reset by a combination of pedal and button presses. That device was to be replaced with a new module according to a Tech Service Bulletin long ago, but maybe that was skipped on your vehicle? Search for more info on that.
https://www.f150lightningforum.com/...he-hv-battery-pack-thoughts.34080/post-630970
"How about just resetting the BMS? To wit:
1. Shut truck down and open door for 20+ seconds.
2. Turn truck on to only Accessory mode (blinking green light on push button).
3. Wait at least 10 seconds.
4. Flash the high beam 5 times, quickly.
5. Step on brake pedal 3 times, quickly.
6. Wait 10+ seconds, watching the red solid battery icon on the IPC.
...the red battery icon will flash several times, and then the BMS is reset.
This can't hurt and might help. Some experienced members here do this every six months."

@Mike G said: The steps for the procedure are listed above, and I have only one small correction to them....after you observe the little red battery icon on the IPC flash several times (step 6 above) and stop.....you need to shut the truck completely off, pause, and then turn it back on fully and go for a drive to charge up.

I wonder if just keeping the truck ON without driving would do the same thing?

 

[chl]

Ditto what @GoodSam said...and think about adding a battery maintainer with an AGM mode, a $40 investment that will save you money (hundreds apparently if you took it to that stealership).

The battery should last many times longer than 3 years if you keep it topped off to 100% as much as possible.

There is more to 12v lead acid battery health than the SOC - it can be one indication of a problem but unless you do a load test, you won't really know the state of health of it.

See this thread for ideas on how to make it easy to add a maintainer..

https://www.f150lightningforum.com/forum/threads/charging-12v-battery.16979/

 

[Superdaddy]

Thank you! I bought the OBD device years ago, I've just not yet used it. I'll follow these instructions.

 

[RocketGhost]

Yeah as others have said you can reset the BMS yourself. No need for a dealer visit. Just buy the battery and replace it yourself.

 

[ZSC100]

 

[potato]

In addition to the OBD dongle + app like CarScanner to get the BMS module's best guess, many of us have added a Bluetooth battery monitor such as the Ancel BM200. Then you can read the voltage at least. This may be more useful since you can read it while the truck is shut down. If you need to fire up the truck for the OBD reader, the truck may be charging already so the voltage will look fine even if the battery is toast.

 

[Jim Lewis]

In addition to the OBD dongle + app like CarScanner to get the BMS module's best guess, many of us have added a Bluetooth battery monitor such as the Ancel BM200.

When you check the Amazon pages for several Ancel BM products, Amazon itself flags the product as frequently returned. It sounds like a good idea, not so well implemented.

 

[TwentyTwentyThree]

Simple. Works. https://a.co/d/0aMm6zuq

 

[Kansan]

When you check the Amazon pages for several Ancel BM products, Amazon itself flags the product as frequently returned. It sounds like a good idea, not so well implemented.

The returns are probably due to misinformed buyers. The BM300 works great and is an awesome tool.

 

[Box Cat]

I use this Victron Bluetooth voltage sensor, https://a.co/d/084tDNOy, quite compact, works great.

 

[ppmax5000]

i bought this after reading a post on this forum. i put my LVB on the charger when i see less than 13volts

https://a.co/d/0dqJQRTg

 

[Mike G]

I'm gonna go against the grain a bit here about using a maintainer. I have used one and have a pigtail connected up permanently to plug one in if I intend on leaving the truck while I'm away for more than two weeks (rare). I did this once while on a vacation two years ago.

But I don't find that it's necessary under normal circumstances. What I do find necessary (as has been mentioned above) is resetting the BMS logic roughly every three months. When I check my stats and notice my 12V SOC is below around 75% on successive days, and I've been actively driving the truck during that time, I will do the "BMS Learned Values Reset Dance" and then immediately go for a drive of at least an hour to fully charge my 12V battery back up.

I did this last week when I noticed my 12V SOC was at 78%, and now it's back up to 90%....and I still have my original 12V battery in my May of '22 built truck.

Can I get away with this forever? No. But it seems to have worked to extend the useful life of the original battery so far.

The steps for the procedure are listed above, and I have only one small correction to them....after you observe the little red battery icon on the IPC flash several times (step 6 above) and stop.....you need to shut the truck completely off, pause, and then turn it back on fully and go for a drive to charge up.

 

[chl]

I'm gonna go against the grain a bit here about using a maintainer. I have used one and have a pigtail connected up permanently to plug one in if I intend on leaving the truck while I'm away for more than two weeks (rare). I did this once while on a vacation two years ago.

But I don't find that it's necessary under normal circumstances. What I do find necessary (as has been mentioned above) is resetting the BMS logic roughly every three months. When I check my stats and notice my 12V SOC is below around 75% on successive days, and I've been actively driving the truck during that time, I will do the "BMS Learned Values Reset Dance" and then immediately go for a drive of at least an hour to fully charge my 12V battery back up.

I did this last week when I noticed my 12V SOC was at 78%, and now it's back up to 90%....and I still have my original 12V battery in my May of '22 built truck.

Can I get away with this forever? No. But it seems to have worked to extend the useful life of the original battery so far.

The steps for the procedure are listed above, and I have only one small correction to them....after you observe the little red battery icon on the IPC flash several times (step 6 above) and stop.....you need to shut the truck completely off, pause, and then turn it back on fully and go for a drive to charge up.

Interesting.
A drifting BMS could be part of the 12v premature death issues leading to charging errors by the truck's regime.

I have not done any BMS resets, but I do use a maintainer (NOCO GENIUS1) all the time the truck is not in use.

My SOC sits at 100% whenever I check it with OBD Car Scanner, and no signs of any 12v battery problems, weird behaviors etc. I don't check regularly because I haven't had any issues.

That said I haven't disconnected it and done an actual test according to standard battery test procedures, to determine the SOH crank current (Cold Cranking Amps), etc.

But I did with my 2012 Nissan Leaf original OEM battery (delivery in Dec 2011) a flooded battery which I have kept on a maintainer since about April 2012 - it got too low when I was a way for several weeks and would not boot the Leaf, so I started keeping it on a maintainer ever since.

I used a UNI-T 673A tester to test the Leaf battery since it was so old.
I was kind of surprised that it still had an SOH of 80% after 14+ years which they say is about the lowest level of 'healthy' so I suppose a new one is in my future?

 

[chl]

Yesterday I towed my travel trailer about 75 miles, parked to register in the office and came out to "Stop Safely". Well it was already stopped so I followed many suggestions listed here:
1) disconnect for two minutes then reconnect, fail.
2) disconnect for five minutes then reconnect, fail.
3) jump start, not sure if that was a suggestion but it also failed.
4) charge the battery, tried to start after battery charger indicated charge complete, fail.
5) wait three hours and try again, it started.

I took it to the campsite, got up and it started so I came home. I couldn't find a replacement cheaper than Ford ($189) so I drove down to the dealer and the service writer (I asked how much installation was), looked up the SOC for yesterday it was at 27% and just before I left the house it was 45%. This he saw this from my VIN number on his computer. He said they need to diagnose the problem (about $365) and if it is truly only the battery install it would be $285 plus the battery because they had to reprogram a module. I asked if I bought the battery and put it in then how much was it to reprogram the module, he said still $285. If I bring it in Monday morning it would be ready Tuesday afternoon. I made the appointment but I will call another dealer in the morning to inquire about the reprograming fee.

So all that got me wondering how can I see the SOC of the 12 volt battery, I see no menu option to get this information.

If you want a really accurate test of the battery without special equipment, you would need to disconnect it, fully charge it, note the terminal voltage with a voltmeter, let it sit for several hours (overnight), then use the voltmeter to measure the terminal voltage again - if it drops a lot from the fully charged measurement, then it has issues.

See this video for example.


Of course you can get even more info using a battery tester, like CCA (Cold Cranking Amps), State of Heath, resistance, etc.

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