Ford BMS issues, research, testing, and solution results

[Snakebitten]

I'd be curious if the drain ceases after a full reset of the truck's 12V system.

What I mean is you clearly have logs showing a fairly consistent drain rate of the battery at rest. So it would be relatively easy to see a contrast in the graph if the drain rate decreased to "normal".

So if/when circumstances would allow, I would shut the truck down and disconnect the battery, but leave the Bluetooth voltometer in operation so that you capture everything the battery experiences, even being free of the trucks 12V bus.

After a couple of hours, reconnect the battery to the truck but do NOT do anything beyond connecting it. No FOB influence. No door opening. Nothing

Then after a few hours Sync the voltmeter data.

Did the truck drain the battery at the same rate that it has been in your previous logs?
Or did disconnecting the battery for a couple of hours successfully put to sleep whatever it is that is part of the excessive drain?

Not really trying to discover exactly what the source of the problem is, but rather confirming the hypothesis that some component is not properly shutting down after the truck gets parked.

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[Ricksc]

I will give this a try today when off work. Thank you for the advice.

 

[Snakebitten]

I will give this a try today when off work. Thank you for the advice.

You don't have to do anything this old geezer suggests. But I admit that I'm now emotionally invested in what the heck is drawing your battery down.

Is it something like the ACM refusing to go to sleep? (just one potential example)

 

[Ricksc]

Last Sunday the battery was out of truck and fully charged. New BMS module and reset. So it would be nice to figure this out.

 

[Porpoise Hork]

While it's not an exact match to your issues there are some similarities with what looks to be random module activation events in key off. I came across this one when trying to figure out why my headlights kept randomly turning themselves on. It's a long video but he methodically goes through diagnosing an odd power drain issue that presented itself with the headlights/tails randomly turning on and off. Might be able to do some similar testing methods he does to narrow down what module is causing the problem.

 

[Ricksc]

Thank you will check it out

 

[Ricksc]

You don't have to do anything this old geezer suggests. But I admit that I'm now emotionally invested in what the heck is drawing your battery down.

Is it something like the ACM refusing to go to sleep? (just one potential example)

2 hours no draw on battery with truck disconnected. Good SOC and voltage. Had rugedraw run vin nothing obvious. Will wait a couple hours re sync and see what happens.

 

[Snakebitten]

That's certainly less drain than when connected to the 12V bus, but I don't think it's nothing. I would expect it to be flat, or even go UP a little.

 

[Ricksc]

Your thoughts? Bad battery? 2 years old.

 

[Ricksc]

For sure much more draw. At a loss for now. Will recharge battery tomorrow and reset bms

 

[Porpoise Hork]

Should be able to hold charge at 2 years but could have heavy sulfate buildup. If your charger has an AGM cycle with auto desulfation could try letting it run to complete a full cycle and then monitor it to see how it holds up.

 

[Ricksc]

I did that last Sunday and full charge with BMS reset.

 

[Ricksc]

Truck has not left me stranded. I have a jump pack. Will ride this out for a bit. Seems to charge up while driving just won’t hold overnight.

 

[Snakebitten]

I just wasn't expecting to see a disconnected battery show visual voltage drop over that 2 hour period.

I do see batteries INCREASE in voltage after recovering from a temporary load. But I would expect a resting disconnected battery sit at a static voltage for hours/days. Or at least the drop would be in .01V over many hours.

I personally don't have the right to spend someone else's money, but I'm convinced a reasonably healthy AGM would sit out on a picnic table without any discernable voltage drop for hours. (as long as there aren't significant temperature swings)

 

[Ricksc]

Going to give it a good charge tomorrow and reset BMS and go from there. It charges fine so…… should be ok. Too many draws on this truck. Will talk to my ford mechanic buddy too

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