Dead Battery! Need electrical advice...

[jaeggernaut]

I came back from a few-week vacation and found my Bronco with a completely flat battery. So flat, I needed to try boosting it multiple times to get the engine to turn over and finally get it going. But I had all kinds of dash lights come on and the breaks were acting really funny. Had the Bronco running for almost an hour and afterwards the battery was still flat.

Towed it to my dealer and the mechanic said there was a strong electrical draw and because of all my aftermarket parts, he couldn't tell me how much the repair would be and it's definitely not covered under warranty.

So, I'm going to try to figure it out myself. Anyone have any clue on what could be going on?

I've added all my aftermarket stuff over the past year with nothing new added since May, with no issues. This is what I've attached that's electrical, ordered from most recent:

- CB radio and antenna (that uses the cigarette lighter for power. It might've been left plugged in. It's at the dealer now and they're not returning my calls) (but, I believe the outlet turns off after a certain amount of time)
- rear and front bumper lights (connected via upfitter switch)
- air compressor (via upfitter switch)
- 'raptor-style' led running lights
- winch (directly to battery)
- rockslide engineering step sliders (disabled via included switch. But I think power still runs to them, since they open and close when trying to boost battery)
- roof lights (via upfitter switch)
- roof lights have a LED running light function

A

ny help would be appreciated. Thanks everyone.

——>
UPDATE here if thread is TLDNR.
I decided it was just parked too long.
30 days. I’m going to follow up with rockslide engineering just in case, though.

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[Jdyount]

So who knows given it's impossible to know exactly how everything is wired.

I would start with the winch, make sure the power cable isn't grounded out somewhere. Given the winch can draw hundreds of amps, in the event of a solenoid failure or a wire rubbing through the cover, I would make sure you have a power disconnect switch mounted very close to the battery.

The air compressor, I would hope you're not actually powering it though an up-lifter given the amperage draw. Having it switched through a relay through the up-lifter sounds better. My compressor draws 22.5 amps so could the AUX1 switch handle it? Yes, but I wouldn't, no way.

I mean ultimately, you're just gonna have to remove circuits until you find the cause. Shouldn't be that hard. Once you're isolated it to the circuit you can trace the wiring to the accessory and find the problem.

 

[da_jokker]

You are corrected at the Bronco will shut off the 12 volts (unless you did the Forscan hack to tweak that).

Upfitter switches all lose power the moment you turn off the Bronco

Also, the Bronco goes into deep sleep after a few days and really shuts things down.

So I would start with those other items, especially the winch). You can use an amp meter to see how much power they are pulling when everything is off.


Question: when you say you left it running for an hour, what was the voltage output on your dash? Did you measure at the battery as well? Should be 13+ at the battery while running, 12+ when not running.

 

[projectbadlands]

I would also suggest start at the winch. Maybe hook up a meter to the negative and positive connector of the winch cables and see if there is a draw happening with it just sitting there.

What you could also do is as the vehicle sits, check the battery voltage and see if it changes as you disconnect each aftermarket component starting with the individually connected components.

 

[wjtinfwb]

Go to Home Depot and buy an inexpensive Multi-Meter (under 30 bucks for a decent one). Connect it to the charged battery with the engine off and doors closed. One by one disconnect the circuits to your added electrical equipment and note the readings on the meter or have someone watch it while you disconnect. When the meter jumps up after a disconnect, you've found your offending circuit to fix.

 

[Owl]

Taking ...FWB's advice a bit farther.

1. Get a cheap multi-meter from Harbor Freight ($8).

2. With a charged battery and everything off... at night check the voltage across the battery and write it down.

3. Check the voltage in the morning... has it changed. If it has, then you are getting a draw-down somewhere. If the draw-down is say 0.3 volts... then a certain amount of amps are being used, and once the battery hits about 10-11 volts it is essentially dead. The volts draw-down though depends on a bunch of factors (like when the computer is on, sleeping, or in a deep sleep). What does "deep sleep" even mean? The fact of the matter is... the computer still has to draw enough power to monitor sensors so it knows when to wake up.

Checking Winch:
4. Set the multi-meter to the "amps" setting.

5. Disconnect the winch, and put the leads from the multi-meter inline with the winch-cable and the battery. See if there is a reading. If there is... this is the problem. If the draw is (for example) 0.25 amps... then the battery will probably be drained completely in say 200-400 hours).

Go to Harbor Freight or someplace and get a relay that can be toggled on/off for powering the winch. It will have to have enough amps to withstand the use of the winch. Hook it up so the relay on/off function is powered by one of the Aux switches.

6. In older cars you could hookup the multi-meter as in #5 for the entire car, but since the Bronco is so computer activated/driven beast when you hook up power... I have no idea how much normal power draw is once it goes to sleep. I believe "Mid" and "High" packages draw more power than the Base package.

Fun fact -- I had a 2001 Mustang. If I left it at an airport (or anywhere) for a couple of weeks then it would be too dead to start. It had no add-on options. That's just the way it was. I had to disconnect the battery (with a manual battery disconnect after this happened a couple of times).

This would be the easiest way to solve your problem (if its not the winch) (i.e. a manual battery disconnect), but I'd talk to the Ford Service guys and ask what happens when the computer is completely disconnected from power for an extended period of time.

O.

 

[Fishwrinkle]

i'm almost in the same predicament. i've already eliminated all my add-ons, but 2 days ago it will go so dead the only way to get it to start is a traditional jump (jump pack and a trickle wouldn't do it, weird). i've been battling it since march and the 1st dealer just started throwing parts at it and i took it back when they wanted to swap the pcm or whatever they call it now. they gave me an f150 with 6 miles on it and it had 2 blinker bulbs burnt in the rear pass light. they wanted to change the bulbs and i said it's more than the bulbs so i'll take a different loaner. 23 f150 with 9 miles on it. quality job 0

 

[Owl]

Well the only thing I can suggest is to get a volt meter that plugs into your cig-lighter in the center console, and check it when the car is running, and when the car is off just after a long run, and then maybe the next day or so. Maybe its not charging correctly???

Also... I'd have battery checked if this persists.

This one would probably work...
https://www.amazon.com/INNOVA-3721-...x=cigarette+lighter+volt,aps,233&sr=8-14&th=1

 

[Happy]

We have all of our add on's running through a distribution block that is connected to the battery through 1 fuse protected 6 ga wire. While I'm certain (mostly) that none of the devices are left on and do not cause a parasitic draw, it is simple to disconnect 1 wire from the battery.
This is the distribution block. https://www.amazon.com/Young-Dance-...-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

You have more connected than we do, so this may not be a good application for your needs.
Even with nothing connected, our Bronco will power down after 6-9 days. At around 15-18 days it has been down enough to not start. Bronco has a lot of battery draw from the factory.

 

[Rydfree]

Well the only thing I can suggest is to get a volt meter that plugs into your cig-lighter in the center console, and check it when the car is running, and when the car is off just after a long run, and then maybe the next day or so. Maybe its not charging correctly???

Also... I'd have battery checked if this persists.

This one would probably work...
https://www.amazon.com/INNOVA-3721-Battery-Charging-Monitor/dp/B000EVWDU0/ref=sr_1_14?crid=1D9PQBV9C4IN6&keywords=cigarette+lighter+voltage+meter&qid=1695417115&sprefix=cigarette+lighter+volt,aps,233&sr=8-14&th=1

The Bronco has a built in battery voltage gauge in the instrument cluster . You just have to toggle to it from the My View screen.

 

[Owl]

I realize the Bronco has an integrated volt meter. I guess I should have suggested that 1st. I guess I like old-school... being old-school.

 

[da_jokker]

The Bronco has a built in battery voltage gauge in the instrument cluster . You just have to toggle to it from the My View screen.

The vault gauge in the dash is just telling you the charging system. It doesn't necessarily dictate what's going on at the battery. It also of course can't measure anything when the Bronco is shut off.

Having a multimeter is a very handy tool. Even the cheap harbor freight one (which I've had for years and has served me well)

 

[Owl]

Yes... the Harbor Freight ones are pretty OK. Not a a Fluke, but pretty much the same readings for the simple stuff (volts, ohms, etc).

 

[jaeggernaut]

…..

Question: when you say you left it running for an hour, what was the voltage output on your dash? Did you measure at the battery as well? Should be 13+ at the battery while running, 12+ when not running.

when I had it running the guage was jumping all over the place. I don’t know if it’s possible but it was like the only electricity was being given by the alternator.
———-

Thanks for all the advice everyone.

the dealer replaced the battery ($325! $240usd) and charged me $65! ($50usd) to do it! What a scam.

I got a good multimeter and once connected in series to the negative battery post, after an initial draw of about 7amps (my side steps initialize even through the power switch that came with the steps is ‘off’. I guess it still goes through an initial Electrical cycle to ‘zero’ the step fitment), after about 3 mins the draw reduces to about 100mA. That feels like it’s high but still reasonable.

at this point, I’m going to drive the car around and just chalk it up to ‘dead battery because not driven enough’. It was parked for at least 30 days.

what do you guys think? Is 100mA still too much that I should start disconnecting everything?

I don’t even understand why something that is ‘off’ would draw power (ie. winch)

 

[Owl]

Depends on how often you run your Bronco, but I would think 100 milliamps isn't that big of draw, as it would take 10 hours to do one amp-hour.

If the Bronco battery is a 100 amp-hour battery (check... as I'm just assuming for this example) that means to draw it down 30% (30 amp-hours) would be 10x30 or 300 hours. 50% draw = 10x50 or 500 hours.

The number of days for a 50% draw-down would be 500/24 = 20.8 days.

If the Bronco is not run for a long period of time I'd suggest getting a trickle-charger (also called a maintainer) that supports AGM batteries... about $30 off Amazon.

If you are parked out in the boonies somewhere you'll have to get one of those fancy solar battery maintainers... about $40-60 on Amazon.

Note: I've never used anything but a standard trickle charger and not on a AGM battery, but just reading the ads it seems they'd work OK as they say they support AGM batteries.

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