Dead Battery

[RogueMetal]

So I have a 2020 Mustang GT with the 401a package and Performance package. The car is also a rebuilt title. The problem I'm having is the car battery is dead every 2-3 days if I don't drive it. It's even worse in cold weather. I might get one day of not driving in the winter before the battery dies. I've had to keep a portable jumb device in the car just because I never know if it"s going to start or not. If I jump the car then I'm usually good for about a day before I have to jump the car. It's beginning to really drive me crazy and I'm wondering if there is anything I can do or buy that would fix my problem. Thanks in advance!

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[loucas-2021]

Given the rebuilt title, the most likely causes are:
1. A module that never sleeps

Especially APIM or BCM. Rebuilt cars often have mismatched modules.
2. A damaged harness

Even a single chafed wire can keep a module awake.
3. Aftermarket electronics

Remote starts, trackers, alarms — all notorious for this.
4. A failing battery + a parasitic draw

The battery is now weak, but it’s not the root cause.

I'd get a parasitic draw diagnosis and go from there.

 

[ORRadtech]

Given the rebuilt title, the most likely causes are:
1. A module that never sleeps

Especially APIM or BCM. Rebuilt cars often have mismatched modules.
2. A damaged harness

Even a single chafed wire can keep a module awake.
3. Aftermarket electronics

Remote starts, trackers, alarms — all notorious for this.
4. A failing battery + a parasitic draw

The battery is now weak, but it’s not the root cause.

I'd get a parasitic draw diagnosis and go from there.

I'd agree with most of this except the bit about the battery not being the root cause. I don't agree with that simply because we don't have enough information. All we know from his description is that the battery keeps dying and he jump starts it. The car charging system is not meant to charge a completely dead battery. Its purpose is to operate the electrics while the car is running and top off the little bit of charge used in starting the car.
The very first thing that needs to be done is to fully charge the battery with a dedicated charger and then have it tested. Preferably with a carbon pile tester but one of the electronic ones will suffice. If it turns out to be bad, then replace it.
Only once you're working with a good, fully charged battery and have verified that the charging system is working properly should a parasitic draw test be done.

 

[Unas2k5]

How old is the battery ? You probably just need to replace it.

 

[Skye]

6G Mustangs and modern cars do have processes that run when the car is shut off. But the load from these is low enough where the car should be able to sit for up to two weeks and still start.

That it's more challenging when the weather is cold is normal. Batteries are taxed when really cold or really hot.

Is this a recent problem? Or have you had this issue since buying the car? If a recent problem, do any other events correlate with that (maintenance, equipment change, mods, etc.)?

Rebuilt title. 2020.

- Check the connections at the battery terminals. Confirm the lugs are firmly attached and there is no corrosion on the cables

- Do a general look underneath the hood, for anything that doesn't look right, loose cables, burnt connections, etc

- Disconnect anything that is not OEM. Radar detectors, audio amps in the trunk, etc. Any physical device that might be a drain. Any size or type

- Disable all services on the car. Bluetooth (802.15), Wireless (802.11), Automatic Sync downloads, etc. Work through the Sync menus and shut everything off

- Keep the key fob out of the car, at least 10 feet / 3m from the door and the trunk when no in use. Keep the fob in a faraday pouch if possible

- Confirm the doors, hood and trunk close well and securely

- Turn any light switches off

- Lock the vehicle when not in use

What is the brand, Cold Crank Amperage rating and age of the current battery? The stock battery is rated at 590 CCA, so what's there now should be at least that. If any less, I'd replace it.

Attached is a photo. If there is an existing Motorcaft battery in the car, look to some raised numbers in-between the fill caps; those will list the date the battery was made. If there is another brand in the car, try to see how old it is. Batteries wear out, no matter how well maintained. Anything past three years is suspect. Anything older than five, I recommend replacing immediately.

The stock battery is a Flooded Lead Acid type. If looking for a replacement, I recommend another FLA. Keep it stock. Keep it simple.

If the battery is replaced, perform a Battery Management System reset. It's simple and takes only moments.

https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

A BMS reset tells the car there's a new battery in it, so it can adjust the charging system accordingly. As batteries age, their characteristics change. BMS adjusts how the charging system works over time.

If the existing battery is younger than five years and rated at 590 CCA or higher, charge it fully. Then perform a load test. It should pass. Parts stores can do a test. If you need to fully charge the battery, you might need to take it to a mechanic and have them charge it overnight.

After the battery is confirmed good, start the car and confirm the alternator is working correctly. Don't test the alternator on a weak or suspect battery. A parts store might be able to check the alternator. A mechanic certainly should.

If all that passes, you've established a baseline. If you've fixed it, great. If not, you might have a short circuit or large parasitic loss. You can t-shoot this by attaching a current meter to the battery and seeing what the drain is. If you're seeing a large load when everything is off, you can pull fuses, one at a time, to see what circuit that is. One you have an area or item of interest, you'll then need to study that circuit and physically inspect it.

T-shooting a short circuit or large loss could be obvious, or might take someone a while to go through the car. Some current loss is expected. Processes are running in the background. But they shouldn't be enough to drain the vehicle overnight.

IDK the history of this car. Given the rapid loss and with the car's rebuilt title, it might be best to keep the car outside until fixed. Not trying to instill drama, but short circuits are powerful. Strong enough to drain systems in moments and start fires. Hopefully, the issue is something simpler, like a bad battery or loose cable.

 

[MSheets]

I have a '22 GT Premium. Mine did that too. I turned the auto update off now I don't have a problem.

 

[FiveOh500]

I'd start with just replacing the battery since it's a 2020 and might be the original one - especially with how much worse it gets in cold weather that screams weak battery to me.

 

[MotoMike]

My '21 never got to an issue with starting but when it was just short of the end of the 3/36 warranty period, I checked the battery with an electronic tester. I wasn't having any starting problems, but I like to check all my batteries going into Winter. The battery checked with very low CCA and screen message was "Replace Battery." Took car to the dealer and they did their check where it also failed and I got a replacement under warranty. They told me the batteries in these only last 3-4 yrs. Mine is a '21 GT Premium coupe with 401a also.

 

[Stangnut]

I have a '22 GT Premium. Mine did that too. I turned the auto update off now I don't have a problem.

Thanks for the tip. I'm going to try that. Ive had batteries die every 2 years in my '19 Bullitt.

 

[gvn49]

Charge battery fully, they sell parasitic draw tester even on amazon, should tell you if you have a draw, which sounds like you do, then you can work from there to isolate the problem, get a battery tender which won't find you problem but shood keep battery charged, if all else failes get a battery disconnect PITA but if battery is good should keep it from dieing, only fix I listed is the parasitic draw tester, good luck

 

[sk47]

Hello; A friend has a new RAM pickup. Only a few months old. He complains of having to jump start if it is not driven for a few days.
I stopped by the shop where i buy my batteries. The shop owner tells me the newer cars somehow monitor the starter voltage and will not operate if below 12 volts. I do not quite follow this.
The truck owner does have the remote start feature. I think the truck is loaded with every electronic gadget possible.
I suggested the truck owner get a float charger. The battery shop owner suggests a battery maintainer.

NOTE- that same owner told me a few years ago that new cars do not charge up by the alternator. That a 20 minute drive likely will not charge up a low battery.

Question- say you decide to shut down things such as remote start and do not know the procedure. Where to find out how to shut that and other such off.

 

[Stangnut]

As far as the alternator, the S550 has a smart alternator. It won't charge the battery under spirited driving so it doesn't take power away from the engine.

 

[ORRadtech]

Hello; A friend has a new RAM pickup. Only a few months old. He complains of having to jump start if it is not driven for a few days.
I stopped by the shop where i buy my batteries. The shop owner tells me the newer cars somehow monitor the starter voltage and will not operate if below 12 volts. I do not quite follow this.
The truck owner does have the remote start feature. I think the truck is loaded with every electronic gadget possible.
I suggested the truck owner get a float charger. The battery shop owner suggests a battery maintainer.

NOTE- that same owner told me a few years ago that new cars do not charge up by the alternator. That a 20 minute drive likely will not charge up a low battery.

Question- say you decide to shut down things such as remote start and do not know the procedure. Where to find out how to shut that and other such off.

Automotive charging systems have never been meant to charge a low battery. They're purpose is to power the electrics of the engine and accessories while the car is running and to top up the little bit of charge used to start the engine. Since modern cars are massively electronic you can figure that very little power goes to recharging the battery.

To your question, with a Ford I'd guess you might be able to turn remote start off with Forscan or Ford's proprietary system. I have zero experience with Dodge so won't even venture a guess there.

 

[tom_sprecher]

Buy one of these for life.

https://www.schumacherelectric.com/products/battery-load-tester/

A good friend of mine has one for years, and with five cars/trucks I borrow it at least once a year

 

[sk47]

Automotive charging systems have never been meant to charge a low battery.

Hello; My first car was a 1957 Chevy with a straight six & a manual trans. I can recall having to jump or roll start that car when the battery was so low the starter would only click. Then driving for maybe twenty minutes and the battery being charged enough to start later on. Same sort of thing for other people's cars over the decades.
Jump the car off and sometimes never have a problem with the battery again. I put a CB radio in my 2004 Chevy Silverado and mistakenly used a hot all the time 12 volt wire to power the radio. I forgot to turn the radio off and a few days later the battery would not spin the starter. I jumped it off and did not have a problem with the battery for many years.
I did power the radio from a wire which is only hot with the engine running.

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