Potential parasitic draw/electrical wonkyness after offroading

[Tharberats]

2 weekends ago, I took my 23 BadSas on a light offroading/rock crawling trip. Spent about 10 hours going all around the area with both front doors off, scraping rock rails and skid plates, but nothing obviously damaging. It did get pretty dusty on the inside.

While in 4lo and not in any GOAT mode, occasionally the Bronco would rev up (maybe downshifting, but didn't act like it) when brakes were pressed, acting like I had accidentally instead pressed the gas. First time that had happened, not the first time I've been in 4lo.

When we were all done, I popped the front doors back on, and after rolling the windows up with the engine off, when we turned it fully off and closed the door, I got the double honk like the keys had been left inside and it was on. Odd, but not troubling.

Over the next week, I started getting more and more little oddities, double honking when I got out, the door locks unlocking (even when already unlocked) when starting the engine, having the auto entry lock the doors instead of unlock them. This built up over the week until I went out and it didn't remote start from the fob and took several presses to unlock it from right outside the door. Got in, tried to start it to get it cooling down, got the very angry rapid beeping and the "parking brake system failure" message, ABS failure, and a bunch of other failures as the bronco failed to start. Turns out, the voltage on the battery was around ~9V. Jumped it, everything running fine, checked the voltage again and the voltage was slowly ticking down. Disconnected the negative battery post, it decided it wanted to continue the flow of electricity and sparked back to the battery, caused a bunch of clicking and headlight flickering that stopped with the sparks.

Oddly enough, that seemed to fix it, but tonight, 5 days later, just got the Ford pass notification my bronco is going into deep sleep to save the battery. Started up this time, but clearly there is still something wonky.

Accessories are total of 4 little ditch lights and a winch. Winch is weird through a marine solenoid and hooked up to Aux 6, been installed since winter 23-24. Lights are wired up to Aux 4 and 5 (1 pair each), and last pair was installed last fall, with no issues so far.

I'm at a loss, thoughts?

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[adam1991]

it's nothing more than a failing battery.

 

[Dan-O]

I would tend to agree with “adam1991”.. classic symptoms of many other posters on here 2-3 year mark. Probably just coincidence that it happened on return of trip.

 

[Tharberats]

Well, guess I'll dig into the battery replacement then, thanks!

 

[PWillette]

Well, guess I'll dig into the battery replacement then, thanks!

When you replace the battery pay close attention to the BMS reset procedure. There are few threads here detailing the procedure.

 

[Tharberats]

So I finally got some time to dig into it. Before dropping cash on a new battery I wanted to double check.

Disconnected the positive terminal and was running a amp meter and got a surprising greater than 10A draw, as it was putting my 10A fused meter into Overload.

Disconnected my 3 accessories (winch, 2 pairs of lights) one by one, no change in the draw, so good to know it's not things I added.

Started pulling fuses 1 by 1. Eventually I got a drop from Overload to ~2A when both "BCM Module B+" and "BCM Module Start/Stop" were pulled. Further investigation led to the last 1.75A drop from the "Sync Module" circuit.

Currently (pun fully intended) the draw with everything off sits at 0.25A. still seems pretty high, so going to keep pulling fuses to see if I can ID another drop.

Any of these sound "normal" to you guys?

 

[Tharberats]

Current state of fuse box

 

[dgorsett]

Whenever I get around my Bronco or Explorer with keys in my pocket (and oddly the Explorer with the Bronco fob) there is all kinds of clicking and clicking. It seems all kinds of stuff activates by your mere presence so it would be hard to isolate.

 

[B22-2023]

Further investigation led to the last 1.75A drop from the "Sync Module" circuit.

That alone seems like a lot of amps for a vehicle that is off and not in ACC mode, and I don’t even get the 10 A+ reading. As @dgorsett said try the tests again with your key out of play, and make sure the doors are closed.

 

[Tharberats]

Yeah, the 10+A reading was nuts to me. So the doors were closed (except for the window as the battery is too low to do it's shuffle down and up as the door opens and closes). I'll charge it up and try again with no key around.

 

[Brian_B]

Any of these sound "normal" to you guys?

Yeah kind of. Whenever you hit unlock or have just shut off the Bronco, there are a ton of things that light off before you even start the engine - all those clicks and whirrs and what not. And when you shut it off, it’s a good few minutes before all the electrical dies down

So a high amp draw immediately after reconnecting the battery is not abnormal - all the computers are booting up and re-initializing and a lot of things wake up. Same deal if you hit unlock, or just open the door, or touch the hands-free unlocks. You don’t have to have ACC on for the Bronco to be doing things

After about 30 minutes of either shutting down or connecting the battery fresh, that’s when you really need to check for your parasitic draw.

There was a spec sheet around here somewhere - may have been in that aftermarket manufacturer white sheet - that after 30 minutes or an hour the total parasitic draw should be less than 200mA (going off memory, will see if I can find that white paper around here)

 

[Tharberats]

So, boosted the battery to ~10.5V, enough to activate the windows so it won't leak if it rains.

Both fobs wrapped in tin foil (poor man's faraday cage) and ~50+ feet away inside the house. No whirrs, clicks or anything.

Disconnected the positive terminal, and checked current. Burst of clicks and whirrs them coinciding with a 10A+ draw, that quickly calmed to ~5A after 30 seconds or so.

Pulled the same 3 fuses, back down to 0.22A.

To sum it up, no real change that can be linked to the fobs. The drop to a stable ~5A draw is probably the same condition, I did not wait that long to see it drop earlier.

I guess next step would be to get the battery checked and or replaced.

Haven't seen anything clearly, but any idea if the standard warranty covers a new battery? I'm at just about 2 years and 23k miles.

 

[Tharberats]

Yeah kind of. Whenever you hit unlock or have just shut off the Bronco, there are a ton of things that light off before you even start the engine - all those clicks and whirrs and what not. And when you shut it off, it’s a good few minutes before all the electrical dies down

So a high amp draw immediately after reconnecting the battery is not abnormal - all the computers are booting up and re-initializing and a lot of things wake up. Same deal if you hit unlock, or just open the door, or touch the hands-free unlocks. You don’t have to have ACC on for the Bronco to be doing things

After about 30 minutes of either shutting down or connecting the battery fresh, that’s when you really need to check for your parasitic draw.

There was a spec sheet around here somewhere - may have been in that aftermarket manufacturer white sheet - that after 30 minutes or an hour the total parasitic draw should be less than 200mA (going off memory, will see if I can find that white paper around here)

I'd be glad to see that white paper if you can find it!

Also, maybe I'm doing this all wrong, where else do you check your parasitic draw besides disconnecting the positive terminal? As I feel that you get that reconnecting the battery surge whenever you then put the amp meter between the + post and the post clamp. Wouldn't that make it real hard to check the amperage 30 minutes after the battery is connected? (I'm working with a standard prong multi/amp meter, so can't just clip it and wait.

 

[Brian_B]

Also, maybe I'm doing this all wrong, where else do you check your parasitic draw besides disconnecting the positive terminal? As I feel that you get that reconnecting the battery surge whenever you then put the amp meter between the + post and the post clamp. Wouldn't that make it real hard to check the amperage 30 minutes after the battery is connected? (I'm working with a standard prong multi/amp meter, so can't just clip it and wait.

two ways to accomplish that

First is a shunt resistor, and you measure the voltage drop on the resistor. They are common for DC systems if you just search for them. You would have to disconnect to install it, but then you would just leave it in for a few hours.

Second would be a clamp-on ammeter. You can get them that read DC amps for not too expensive, but you have to make sure it reads DC amps, most of the really inexpensive ones only read AC amps.

I found the document I was thinking of, but it didn't have the specification I was remembering =/ so win one, lose one.

I'll link that document here, it has some interesting stuff, but not the parasitic draw.

https://www.bronco6g.com/forum/threads/2024-bronco-equipment-install-guide-official.89188/

If I can remember where I saw that (It was around these forums somewhere) I'll circle back around and post.

 

[Brian_B]

I'll also say my battery crapped out after 2 and a half years, give or take. I wouldn't say it's common, but it's not exactly uncommon for these AGM batteries either. In my case, It took a 300 mile trip to charge it fully by just driving, and it was back in deep sleep about week later. It never failed to start the Bronco, but I did get some weirdness before I noticed it was dying, and the dreaded repeated Deep Sleep notifications before I finally just upgraded it.

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