Odd battery problem any suggestions?

[Northeast]

Long post but hoping for some insight on an inconvenient problem.

I have a 23 Ecoboost with less than 2k miles on it. Twice now it’s had a dead battery sitting in the garage. The first time, about 6 weeks ago, after checking for loose connections at the battery terminals and putting it on a charger overnight I took it to the dealer to have it checked since it’s under warranty ( and it also needed a couple small adjustments). They kept it 2 days, charged and tested the battery, and told me it was fine. They asked if I had any aftermarket stuff and if maybe I was making short trips and there wasn’t time for it to charge.

I did have a radar detector connected using the power port under the infotainment screen, and I wasn’t 100% sure that wasn’t to blame, so I kept it unplugged for a while and no troubles. Then I guessed that power port does not shut off with the ignition, bought a hardwire kit, and connected it to a fuse that for sure switches off (heated steering wheel). I set up the gauges so I can watch the voltage (always shows charging at about 14V when running) and everything was fine until today.
Both times this happened I got a message in the Ford app that the car was shutting down communication due to low battery power.

So now I’m not sure how to proceed. I’m pretty confident the radar detector was never the problem. Is it possible that I’m just not driving it enough? It’s true that it often sits a couple days and makes short trips, but our other cars have been driven even less without this kind of problem. Is the factory battery undersized? If so I’ll gladly upgrade it myself. Or, is it possible for a battery to be defective in this way? All my experience has been with gradual, not sudden/intermittent failures. I expect that a charging system failure would throw a CEM right?
Any of this sound familiar? Do you all keep the Mustang on a tender?

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[Farkel]

Tender for sure, especially with the way you describe how it gets driven. These cars have considerable parasitic draw.

 

[ORRadtech]

Not normal, no. You should get a few weeks with no problem.
There have been reports of new cars sitting on lots with a discharged battery to the batteries detriment.
You likely have 1 of two things happening. Either it's a failing battery or an intermittent parasitic draw.
I'd take it by a local auto parts store and have them load test the battery and go from there..
I'd hope for it being the battery as parasitic draws are hard enough to find much less an intermittent one.

 

[ORRadtech]

Tender for sure, especially with the way you describe how it gets driven. These cars have considerable parasitic draw.

What he describes is not normal.
My '18 EB can sit for two or more weeks with no problem. And I have an automatic phone holder/charger plugged into the power point at all times.

 

[Johnny Rockit]

From what I have read here, a load tester will not do much good on these cars. I forget the technical reason but search the forum, the info was posted.

 

[young at heart]

I just replaced a perfectly fine battery in my 2020 GT convertible because it was almost three years old and I prefer not to take chances. But it was showing zero signs of any weakness at all.
And the car is a pretty day toy so it has gone 2 months + several times without being cranked or run.

Based on my experience I’d say something ain’t right in your case. Big time.

Oh, and no tender or anything.

 

[Johnny Rockit]

My car sat in the showroom for a long time until this sucker came along. It had to be jumped two times before my road test. And I stalled it at a light but thankfully popped the clutch out of experience as I was moving enough to fire it up. The "new" battery was junk and it was replaced that night after I paid for the car. The alerts on the app kept me informed as to what was done and when with respect to the battery.
As soon as I got the car out of storage, it got the tender pigtail installed. It may go a few days without being on the tender but when I take it out for a ride it is never to the store and back. If it is not at least an hour trip one way I make sure to find the circuitious route to put some miles on the car.
Not sure if the alerts are even on the app any more.

 

[Johnny Rockit]

Alerts gone.

 

[Northeast]

Thanks for the feedback, I’m going to get the battery tested at auto zone and see what they say. It’s not that I don’t trust the dealer but they didn’t really help despite having it for 3 days. I also ordered one of those voltmeters that plugs into the cig lighter so I can keep an eye on it. I’m loving this car and don’t really mind fiddling with it, but this could get old pretty quickly.

 

[Jackismydog]

2023... I would go to the stealer right away...This must be covered

 

[paulm1]

how close is your key fob to the car when you're home?

 

[Johnny Rockit]

Document everything.

 

[Northeast]

how close is your key fob to the car when you're home?

Maybe too close. I read some of the many threads around battery issues here and learned about the key fob “wake up” someone described. Key is usually in the bedroom, which is above the garage, and maybe 20’ from the car, which I leave unlocked. But, I’ve had 3 Volvos with similar connected features and no troubles. Although I think Volvo batteries are oversized compared to other brands, so maybe that’s the difference.

 

[Cory S]

Tender for sure, especially with the way you describe how it gets driven. These cars have considerable parasitic draw.

It’s not much draw at all. Usually under 40mA. My car can easily sit for 30-35 days with the car locked, alarm enabled with only a small 30Ah battery that’s only 1/3rd of the size of the OEM 96R group size battery.

 

[Farkel]

It’s not much draw at all. Usually under 40mA. My car can easily sit for 30-35 days with the car locked, alarm enabled with only a small 30Ah battery that’s only 1/3rd of the size of the OEM 96R group size battery.

Duly noted. I thought I had read that somewhere in the forum. Thanks.

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