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

[RLXXI]

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?

I would have to teach you the way I was trained in how to detect these things and I'm no teacher. We were taught to look for current draw as you can have full voltage on a circuit that's just potential power, it's nothing until it starts moving (current flow).

Once you isolate the current flow circuit, then you can isolate components via voltage drop which really only helps in detecting bad connections, grounds and such. Does nothing for a circuit that's energized by a working component, in that case it would show no voltage drop provided there are no bad connections.

In short forget about voltage entirely, current flow is what you want to look for. Isolate the circuit then pinpoint from there.

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[lister coggs]

I would have to teach you the way I was trained in how to detect these things and I'm no teacher. We were taught to look for current draw as you can have full voltage on a circuit that's just potential power, it's nothing until it starts moving (current flow).

Once you isolate the current flow circuit, then you can isolate components via voltage drop which really only helps in detecting bad connections, grounds and such. Does nothing for a circuit that's energized by a working component, in that case it would show no voltage drop provided there are no bad connections.

In short forget about voltage entirely, current flow is what you want to look for. Isolate the circuit then pinpoint from there.

Ok, I think I get it. Detecting amperage (current flow) on each circuit while the vehicle is off would be the most accurate way of determining which circuit is pulling power from the battery.

My graph was looking at the voltage of the battery itself as an indicator of parasitic drain, rather than the voltage of any individual circuit. The declining voltage of the battery is indicative of parasitic drain.

Either way, before I start tracking amperage to narrow which circuit, I'm going to try FORscan to see if it can tell me which modules aren't sleeping.

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In a related note, while trying to use my thermal camera on the fuse panel, I've had the vehicle alarm repeatedly go off. I noticed that no matter what I do, I can't get the alarm system motion sensors to stay off. They keep turning themselves back on even after setting the menu in the system.

Going to experiment more once I get FORscan running, but perhaps this is related to the parasitic drain issue.

 

[mr.Magoo]

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.

You woke up the truck by opening the door, polling the modules via OBD will keep them awake and/or wake them up even though the truck is otherwise off, hence drawing a lot of power.

This is the reason why I monitor the 12V supply to the dongle so that I don't keep making requests once the truck is off - as that would drain the 12V / LVB battery.

 

[Adventureboy]

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.

Make sure you don’t take PAAK or key fob when you go out to take the picture.

I can't get the alarm system motion sensors to stay off.

Try turning WAL off and leaving it unlocked. This should keep the alarm from arming.

There is a second fuse box near the firewall under the passenger frunk cover. That one will be harder to get an undisturbed picture.

 

[srspring551]

Does anyone know if it makes a difference if I hook up the ANCEL BM200-US upstream or downstream of the BMS? I would think not but....

 

[Adventureboy]

Does anyone know if it makes a difference if I hook up the ANCEL BM200-US upstream or downstream of the BMS? I would think not but....

It doesn't matter on a monitor like this since it uses so little power. The absolute purist would hook it to the positive terminal and the truck side of the BMS, but the readings will tell the story either way and the BMS and battery won't know the difference. In either case, make sure you have the monitor on the top closest to the nut and not between the main cable and the battery connection.

 

[Adventureboy]

@lister coggs did you manage to get your drain issue sorted? I'm curious what was causing your problem.

 

[lister coggs]

@lister coggs did you manage to get your drain issue sorted? I'm curious what was causing your problem.

Nothing yet! Ford had my vehicle for a couple of days last week. At first, they said the terminal bolts were loose again (I'm pretty sure they weren't), then they had it for another day and said they were having trouble with it, but were able to reduce the draw from 6 amps to 1 amp. I had to take the vehicle back for the weekend, and I'm giving it to them again tomorrow.

I put the monitor back on last night. The symptoms are the same as before I gave it to them (SOC stays at 100% when the HV battery is plugged in, drops immediately when not connected).

I don't know how much it will cost to have Ford investigate this issue. I was under the impression they charge for time spent diagnosing, which could cost a fortune since they don't seem to be familiar with the issue. I found this video on checking parasitic draw and might give it a whirl later today:


I have a feeling that it might be related to the motion sensor refusing to turn off as I hear that is a common culprit.

 

[Adventureboy]

I think there are multiple motion sensors all connected to the BCM so I expect it isn't a simple thing to track. Keep us in the loop - I'd like to see what they track it to.

 

[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.

If you're curious, I tried an infrared camera on the passenger fuse panel and this is what it showed.

I tried taking the top fuses out and the parasitic draw remained, though, so I gave up on that technique.

I

 

[mr.Magoo]

If you're draining your 12V battery in 1.5 hours it's pulling around 15A which is a heck of a lot more than "parasitic" drain and as such it should be fairly easy to track down.

Personally I'd start off with getting a cheap clamp meter, stick it on both positive and negative leads to verify that it's more or less the same, then leave it on either one and start pulling fuses until it redicuces / goes away (it'll be faster if you have someone keep an eye on the meter while you pull fuses), once you know which fuse you now know which direction to look, rather than fumbling more or less in the dark.

Just keep in mind that the truck will wake up when you open the doors and it'll take 10-15min to go back to "sleep", so you'll have to give it that time. It would buy you some more time if you were able to hook up a charger / powersupply.

 

[bmwhitetx]

Personally I'd start off with getting a cheap clamp meter, stick it on both positive and negative leads to verify that it's more or less the same, then leave it on either one and start pulling fuses until it redicuces / goes away (it'll be faster if you have someone keep an eye on the meter while you pull fuses), once you know which fuse you now know which direction to look, rather than fumbling more or less in the dark.

This is an excellent idea. I would just note that most cheap clamp-on meters you find at Lowes or Harbor Freight will only do AC current (much easier to do). You will need a clamp-on that does DC current. Those are usually more expensive.

Look at the specs, they will all say AC/DC voltage, but will likely only says AC amps. You need one that says AC/DC amps. The symbols on the meter tell you which:

 

[lister coggs]

This is an excellent idea. I would just note that most cheap clamp-on meters you find at Lowes or Harbor Freight will only do AC current (much easier to do). You will need a clamp-on that does DC current. Those are usually more expensive.

Look at the specs, they will all say AC/DC voltage, but will likely only says AC amps. You need one that says AC/DC amps. The symbols on the meter tell you which:

Great call out. It looks like the cheap one at Princess Auto (Canadian Harbor Freight) will do AC/DC. https://www.princessauto.com/en/mini-digital-clamp-meter/product/PA0008344707

Will give that a go later today.

 

[bmwhitetx]

Great call out. It looks like the cheap one at Princess Auto (Canadian Harbor Freight) will do AC/DC. https://www.princessauto.com/en/mini-digital-clamp-meter/product/PA0008344707

Will give that a go later today.

It looks like that one will only do AC amps, not DC. It has the sine wave symbol next to the 20A, 200A, and 400A scale. That indicates AC only.

If it did DC there would be a horizontal line with three dashes below it. Note for the Volts scale there is a setting for 300V AC (sine wave) and 300V DC (line with dashes).

 

[lister coggs]

It looks like that one will only do AC amps, not DC. It has the sine wave symbol next to the 20A, 200A, and 400A scale. That indicates AC only.

If it did DC there would be a horizontal line with three dashes below it. Note for V=Volts there is a setting for 300V AC (sine wave) and 300V DC (line with dashes).

Great call (again).

From the description: "Measures AC/DC voltage, AC current".

I'll probably just set up my regular multimeter for the testing. Confirmed it can measure DC current.

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