12V Battery SOC Tips

[Logal727]

So does the BECM not do anything anymore? Lol

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[Fremont Kid]

I have about a 25 mile drive home and then will be at the gym so I will leave it running while there and see what happens.

Mark and Zombie, could you explain what "...leave it running..." means? Either the power is engaged/on or it is off, correct? No engine is running/combusting. Thanks.

 

[Mach-Lee]

Mark and Zombie, could you explain what "...leave it running..." means? Either the power is engaged/on or it is off, correct? No engine is running/combusting. Thanks.

Leave the car on in park. You'll have to disable auto shutdown timer in the settings so it doesn't turn off after 30 minutes.

 

[ZombieJester]

Leave the car on in park. You'll have to disable auto shutdown timer in the settings so it doesn't turn off after 30 minutes.

Yup. and I turn off climate control, radio and lights.

 

[ZombieJester]

Well after 5 hours you got it up to 95% but it still didn't want to install. Suggested next steps are an external battery charger, or disconnecting the negative battery terminal to do a 12V reset.



You'd want to make sure the car charges for at lest 6 hours, e.g. 50% to 100%. Having it plugged in without charging does not help.

Guess I will need to do some youtube searching. I am not car savvy at all unfortunately. Not a good user experience and thanks again for the tips.

 

[Fremont Kid]

Yup. and I turn off climate control, radio and lights.

OK, thanks. One additional question.
Is there any value to maintaining the ICE term 'running' when referring to BEVs?. I'm not challenging, just wondering if I'm missing some functional or system understanding that warrants the term.
I am diligently eliminating all ICE terms that could be confusing, e.g. gas pedal vs accelerator; transmission vs drive setting.
Thanks in advance.

 

[ZombieJester]

OK, thanks. One additional question.
Is there any value to maintaining the ICE term 'running' when referring to BEVs?. I'm not challenging, just wondering if I'm missing some functional or system understanding that warrants the term.
I am diligently eliminating all ICE terms that could be confusing, e.g. gas pedal vs accelerator; transmission vs drive setting.
Thanks in advance.

Nope, that was literally me just using an outdated term.

 

[ZombieJester]

Final update from me on this one:

I did some research on this forum and YouTube yesterday. I wondered if when they replaced my 12V a few months back if they didn't reset the BMS. I reset the BMS yesterday and went to a concert last night. When I got home I re-scheduled the update for an hour earlier and to my surprise it finally installed. I don't know if the BMS thing is a coincidence but just glad it worked.

Anyways, thanks for all the help on here.

 

[Teslaeata]

Hi Everyone,

2021 Job 2 EAP here.

About 4 months ago my MME was failing to do updates. After some diagnostics with the Ford team we found that my 12v was not keeping SOC at all. Put it to the dealer and they installed a new 12v. 3 or 4 updates since then have gone great. My MME was recently at repair for 2 weeks as I was backed into in my work parking lot. I have the car back and received my latest update yesterday which has failed 4 times to update. I am really hoping the 12v isn't faulty again from sitting at the repair shop.

Any tips on how I can get the 12v up to speed again? Was going to try the "leave it on for 8 hours in the driveway" tonight to see if that works. Crossing my fingers It isn't just bad luck and I have to drop it off again.

Thanks for the time and suggestions!

There’s no benefit leaving car turned on because DC/DC converter charges 12v when reqd even when turned off. If 12v batt is good and DC/DC is good, shouldn’t be a problem, don’t overthink it is my recommendation.

 

[iam-s-Hon]

This is all great stuff as I am not very smart when it comes to car stuff outside of the standard tech. Looks like I need to look into getting CarScanner and one of the dongles so I can check my SOC.

I got one and found it helpful to confirm some data, especially since there's lot's of history on the site.

I get an occasional 'electrical drain' message due to my dash cam. So having some data to confirm SoC etc is useful, like if I plan to park my car somewhere not-at-home for a few days.

 

[kennethjk]

I'm going to interject here, it actually can take a very LONG time to get to high SoC. It charges quickly at first, but the last 10-20% is very slow.

Looking at my history, on a recent test it took 35 minutes to go from 80% to 90% SoC. Above 90% it gets really slow, like it could take another hour or two to reach 100% from 90%.

The problem is a lot of these OTA updates want very high SoCs, and because of the kinetics of lead acid charging it takes a long time to get the battery that high.

I told him to try leaving it on for a couple hours, that does work for some people that can't put a 12V charger on it.

I drove 4 hours home the other day and the LVB barely got above 90%

 

[JimmyMachE]

I get an occasional 'electrical drain' message due to my dash cam. So having some data to confirm SoC etc is useful, like if I plan to park my car somewhere not-at-home for a few days.

What is your 12V battery standby drain/Quiescent average mA in Car Scanner? How many % SOC does the 12V battery lose overnight with the dashcam in parking mode?

 

[iam-s-Hon]

What is your 12V battery standby drain/Quiescent average mA in Car Scanner? How many % SOC does the 12V battery lose overnight with the dashcam in parking mode?

Great question... haven't taken time to measure and record it. I unplug the camera when at home. I use a cam setting to shut off park mode when it dips. It hasn't been much an issue in warm weather except when I was out of town for about 6 days and car was parked away from home and returned to low V warning. Car started up ok but something I'm more concerned about in cold weather if I fly out of town for a few days.

 

[JimmyMachE]

The 12V standby drain (quiescent average) is constantly measured 24/7 by the vehicle. What you see with obd2 dongle is the average standby drain from the last 24 hours or even longer.

It takes 20 seconds to connect the obd2 dongle in the evening, read the 12V SOC and Standby (quiescent) mA, then disconnect the obd2 dongle before locking the car.

After the dashcam was running all night in parking mode, next morning connect the obd2 dongle again and read the 12V SOC and Quiescent.

The aux battery could get a top-up during the night from the HV battery, so I would take more samples on consecutive days.

 

[AtomicInternet]

I'm planning on running these to my charge port somehow. I already have a 12v charger with this cord for my other car, so it'll just be plug and charge no need for clamps/etc. Haven't taken much time to figure out how, but having the 12V cable available to charge as well as the main battery from the same door is pretty convenient. I might just plug them both in every night to maintain charge. Thoughts?

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