"Electrical System Drain. Service Required." DIY Fixes?

[lister coggs]

I believe the issue was on his end. He said he ”was disconnecting the battery entirely” to charge it - instead of just connecting the charger to the jump points. So very likely has not been reconnecting it tightly.

This is correct. I didn't ratchet-tighten the terminal clamps because I kept removing and reseating them to charge it manually during troubleshooting. They were tight and making contact, just not extremely secure (they could wiggle off with some force).

Either way, last night the message (Electrical System Drain. Service Required) reappeared as expected, so this was unfortunately not the issue.

I wonder if there's a better way of finding a dealership that knows more about these vehicles? It seems like they're more used to either ICE vehicles or unfamiliar with modern systems and common errors. Looking on this forum, it seems like this is a re-occurring problem with both Lightnings and Mach-E's. Maybe I should go to a dealership in the closest major city instead? (Toronto)

The fact that they were driving the vehicle around after tightening the battery terminals, trying to replicate a parasitic drain issue, seems like they might not fully understand the problem.

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[RLXXI]

Yes many ways to bring the battery back up to 100%, but I think letting it drop to 16% could be problematic over time.

The ups and downs of a deep discharge (like down to 16%) then charge with a current to bring it back to 100% in 1 hour of close to 30A (from 5.6Ah to 35Ah = 29.4Ah; 29Ah/1h=29.4A) can't be great for the battery in the long run.

A trickle charger goes much slower (lower current) which is better for battery longevity so they tell me.

Because some have reported parasitic draws of a significant level when off/idle, and my truck sits idle for a day or more sometimes depending, a trickle charger works better for my situation (nice to be mostly retired in my case).

I'd like my 12v battery to last a lot longer than the 3yr B-to-B warranty.

Now that the weather here in the N. Hemisphere is getting colder, keeping the batteries (LV and HV) on chargers when off seems prudent.

But to each their own.

Bought the truck in June and have the same commute the entire time, I don't think it's as problematic as you seem to believe. That's 5 months of those short trips and it hasn't killed the battery yet, and only 1 hour to bring it back up. This is SOC we're talking about, not voltage. There is a difference.

 

[K6CCC]

Watching this thread. 24 Flash that I bought in February 25 with a little over 14K miles. Thursday evening drove about 18 miles round trip to dinner and plugged in the truck to my FCSP overnight. It was only down to 69%, but it was convenient to charge. Location charge set to 90%. Middle of the night I checked my phone to confirm it was completed and got an error message about no comm to the truck and it needed to be driven (sorry, don't remember the exact wording). Got up later and my phone showed the truck had completed the charge at 0247 (as expected) and all was fine. Friday I did two trips totaling 11 miles without incident. This morning, phone shows a message of "Electrical System Drain Service Required". A few hours later I needed to move the truck out of the driveway and the dash showed the same thing.
The only thing plugged in is a GPS that is plugged into a 12V outlet that the truck turns off 30 minutes after shutting off the truck. I also do have an OBD2 reader plugged in that I will use shortly to check for error messages and various electrical status.

 

[K6CCC]

Well, this is interesting. Shortly after I posted the message above, I went out to the truck, got in, and brought up CarScanner. Note that the truck is in Silent Mode so no lights were on. I did not turn on the truck. It was showing a 12 amp load on the 12V battery which changed to a 6 amp load a minute or two later. Voltage was just over 12 volts. Turned on the truck and immediately saw the voltage climb to over 14 volts and charging current to 60 amps. The current tapered off fairly quickly. Used CarScanner to read DTC codes and saved them. It's a long report so I'm not going to post it here, but it can be read in it's entirety at: http://k6ccc.org/DTC_2025-11-29.txt
Below are screen captures of the CarScanner LVB page through this. You can see the time from my phone at the top of each image

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[RLXXI]

Well, this is interesting. Shortly after I posted the message above, I went out to the truck, got in, and brought up CarScanner. Note that the truck is in Silent Mode so no lights were on. I did not turn on the truck. It was showing a 12 amp load on the 12V battery which changed to a 6 amp load a minute or two later. Voltage was just over 12 volts. Turned on the truck and immediately saw the voltage climb to over 14 volts and charging current to 60 amps. The current tapered off fairly quickly. Used CarScanner to read DTC codes and saved them. It's a long report so I'm not going to post it here, but it can be read in it's entirety at: http://k6ccc.org/DTC_2025-11-29.txt
Below are screen captures of the CarScanner LVB page through this. You can see the time from my phone at the top of each image

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I got that message once and it was directly caused by the obd dongle I left plugged in. Unplugged it, message went away never to return.

 

[lister coggs]

It can be expensive to have the dealer update every module outside of warranty. The process would take at least a day in the shop - likely 2. Some of us bit the bullet and bought the connector (and a big power supply) and get a temporary FDRS subscription periodically to update our own trucks from time to time. As with anything in the computerized world, there is some risk associated with doing this but the cost is way cheaper than paying the dealer to do it.

I installed one of these: https://www.amazon.ca/ANCEL-BM200-Bluetooth-Automotive-Lead-Acid/dp/B0BZ8D71NY/ref=sr_1_5?crid=8B8INSGJOJK9&dib=eyJ2IjoiMSJ9.kdXgPqlQ-syUk-UeC0Qd1lIIQkwKP1PEfDgC2c-uFN4aZPsN_V9blfyBCJ8xsLkOuDOOXlT2LdTGwW7kD9eLQ3IlF_XDcuQLsCSFyJ0oUzbB1YJ1ft5TDrOt18a6oBs_m7KsRNa7sk0J7iVGuqUmHriRHifzzU56SwHbgF8RIk_dyCMqzKWGvJ_HypdtYDqy7VgkMhGAJYmnG1qwOf3a6d6P1wWcwkMII7SNlPNODdZo8gmF9fdLvZL6CtT9KeoplIjtIBrv45warAyISj1W2SMM3bkcDNkjxs5FUEi-N1c.7qXSGv_e4gSxms4AlQS0S2NFygMF-jCcPQ6Yr4t_rVY&dib_tag=se&keywords=battery+monitor&qid=1764356609&sprefix=battery+monitor,aps,108&sr=8-5&th=1

It was invaluable in tracking my 12v problems. I have it installed in all 3 of my vehicles now.

I see you are in Barrie. I'm Richmond Hill.

Got Bluetooth monitor installed, nice recommendation. After parking the vehicle the battery immediately begins discharging over about 3 hours, then once it hits 15%, the HV battery recharges it to 100%. This was with the vehicle not plugged in.

I'm assuming these constant cycling can't be good for the battery. I wonder if it's possible with forscan to adjust these numbers so it's not fully discharging or charging.

 

[Adventureboy]

@lister coggs you have a serious parasitic drain problem. The pattern indicates you are pulling around 6 amps continuously if your battery is healthy. It seems your truck is not shutting down properly due to some condition like a door ajar or something similar. It takes about an hour to charge a healthy battery and your charge cycle looks about right.

 

[RLXXI]

Got Bluetooth monitor installed, nice recommendation. After parking the vehicle the battery immediately begins discharging over about 3 hours, then once it hits 15%, the HV battery recharges it to 100%. This was with the vehicle not plugged in.

I'm assuming these constant cycling can't be good for the battery. I wonder if it's possible with forscan to adjust these numbers so it's not fully discharging or charging.

You're confusing SOC with battery voltage.

 

[lister coggs]

@lister coggs you have a serious parasitic drain problem. The pattern indicates you are pulling around 6 amps continuously if your battery is healthy. It seems your truck is not shutting down properly due to some condition like a door ajar or something similar. It takes about an hour to charge a healthy battery and your charge cycle looks about right.

It doesn't look good. Lol.

There's no physical evidence of door ajar, lights on, etc. Nothing like that.

I have another appointment with dealer booked for Thursday. In the meantime, I'm going to get a FORscan adapter. Looks like you can monitor module sleep states with that.

 

[lister coggs]

You're confusing SOC with battery voltage.

I understand they're interconnected measurements but technically different. In my diagnostics of the parasitic drain how is this difference relevant? Am I overlooking something?

Here is the same chart with voltage over time which shows a similar trend.

 

[Adventureboy]

The monitor only estimates SOC based on the voltage trends so it can be off a bit since it doesn't directly track the current in/out of the battery like a BMS, but it is close enough to show the trends pretty clearly.

The voltage chart doesn't show the SOC trends as well, but it tells the same story. Something isn't shutting down properly in the truck. I'm curious how many cycles it will charge/discharge before going into sleep mode. On my 2023, it would only do it once initially. Ford updated that charge profile sometime in 2024, I think.

Another thing to watch. When the truck goes into sleep mode, does the drain still happen?

Any chance you have or know someone with an infrared camera? If you point it at the fuse box and snap an infrared photo about an hour after shutting down, without a keyfob or PAAK around it may tell you which fuse is carrying the current. The problem is you need to sit in the truck and wait for 45 minutes to get the picture since opening a door will light up the modules.

 

[RLXXI]

I understand they're interconnected measurements but technically different. In my diagnostics of the parasitic drain how is this difference relevant? Am I overlooking something?

Here is the same chart with voltage over time which shows a similar trend.

When you have a parasitic draw you don't look at voltage or SOC, you monitor amperage.

 

[K6CCC]

I got that message once and it was directly caused by the obd dongle I left plugged in. Unplugged it, message went away never to return.

Interesting. Yes, I have left the OBD2 dongle plugged in for quite a few months.

 

[lister coggs]

The monitor only estimates SOC based on the voltage trends so it can be off a bit since it doesn't directly track the current in/out of the battery like a BMS, but it is close enough to show the trends pretty clearly.

The voltage chart doesn't show the SOC trends as well, but it tells the same story. Something isn't shutting down properly in the truck. I'm curious how many cycles it will charge/discharge before going into sleep mode. On my 2023, it would only do it once initially. Ford updated that charge profile sometime in 2024, I think.

Another thing to watch. When the truck goes into sleep mode, does the drain still happen?

Any chance you have or know someone with an infrared camera? If you point it at the fuse box and snap an infrared photo about an hour after shutting down, without a keyfob or PAAK around it may tell you which fuse is carrying the current. The problem is you need to sit in the truck and wait for 45 minutes to get the picture since opening a door will light up the modules.

Wow, that's genius. I have a thermal camera I use for detecting thermal leaks. I'll give that a try. It's consumer grade though, so might not be sensitive enough for those tiny fuses.

I can probably just use a screw driver to close the passenger door latch to have the vehicle think it's fully closed.

I'll keep an eye on 12V when the truck is in deep sleep mode as well.

 

[lister coggs]

When you have a parasitic draw you don't look at voltage or SOC, you monitor amperage.

Tracking amperage seems like it would be the most precise way to monitor parasitic draw.

That said, can't I calculate amperage from the voltage drop data I already have? (I.E. I can calculate rough amperage from battery capacity, SOC or V drop rate / time period.)

Also, even if amperage is the most accurate way of detecting parasitic drain, wouldn't a repeatedly draining SOC / V still be a sufficient indicator? What else would that possibly be?

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