Battery Maintenance for the Summer

[Tommy G]

We will be leaving hot Florida for the mountains of North Carolina from June until mid-October. We have done this every year since 2017 with our Chevy Volt just left left behind plugged-in. When returned, the car was charged and the 12V battery maintained. Our 12V battery lasted 7 years. Batteries in Florida are lucky to make it for 3.5 years. I keep the 2019 Corvette on a trickle charger and it lasted 7 years as well. It also sits in the same garageas did the Volt. Our Outback is used to go back and forth to the mountains stays on a charger during winter here and it holds a charge as well. From what Ford is telling me, I am supposed to just charge the Mache to 50% and disconnect the 12V for that time period. I makes no sense to me. I am not storing the vehicle. Pages 171 and 175 of the owners manual clearly note that the HV battery services the 12V. So why is all this disconnect when I am setup on the home charger to run from 11 PM - 5 AM every day? This seems like an awful lot trouble. Leaving the 12V to sit in the heat seems like a good way to kill a good battery. Why can I not leave it plug-in at 60-80% and let the HV battery do its thing?

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[AustinMachE]

Isn't the recommendation in the manual for long-term storage when it can't be plugged in for charging?

Just drain to 50-60%, set charging to 50-60% max, plug it in, and head on out.

 

[RickMachE]

So June to mid-October is not "storing the vehicle"? Ok...

Unplug 12v, put on battery tender.

Some updates reset charging parameters, resulting in 100% charge.

 

[E90alex]

What do you mean you’re not storing the vehicle? Leaving it not driven for months is the literal definition of storage.

50% is ideal for the HV battery to be at when sitting unused.

The 12V battery is charged when the HV battery is actively charging. If it’s sitting at the charge limit, it’s not going to charge the 12V, even if it’s plugged in to the car charger.

So in your scenario of just leaving the car plugged in, the 12V will not be charged everyday and will just continue to drain because it’s still constantly supporting other 12V functions in standby while parked. eg door lock system and communicating with Ford servers.

And your reasoning about leaving the 12V “sitting in heat” makes no sense. It’s going to be sitting in the same heat regardless of being charged or not. The 12V is not cooled.

If your garage sees extreme heat then I would drain the car to 50%, set charge limit to 50% and leave the car plugged in so it can cool the HV battery as needed. And get a battery tender to hook it up to the 12V jump posts (not directly to the battery terminals) to keep the 12V maintained.

 

[Teslaeata]

12V battery will charge if HVB has more than something like 15% whether car’s plugged in to charge or not, battery management sees to that.

I’d charge to 80% and just forget it

 

[luckie]

We will be leaving hot Florida for the mountains of North Carolina from June until mid-October. We have done this every year since 2017 with our Chevy Volt just left left behind plugged-in. When returned, the car was charged and the 12V battery maintained. Our 12V battery lasted 7 years. ... Why can I not leave it plug-in at 60-80% and let the HV battery do its thing?

Well, yes, this just reminds me, the Chevy Volt was so very smartly engineered and I'm not sure how why it ended up that way. I recall on the Volt forum everytime we were discussing "Hey, will the 12V charge?'" or "Wait, is the car going to tell me how long...?" an engineer from GM would post "Yep, we set it up to do that for..."

I guess the Volt project was a halo project for GM, a point of pride, Bob Lutz wanted to show GM could make a cool EV, potentially cooler and certainly more affordable than Tesla. Maybe the engineers were given more leeway to do things really well?

Interesting to me, I think the Volt was kinda reincarnated a few years ago in the 2023+ Prius Prime. Happy to see that. I do think a PHEV with 50+ miles EV range can help move a bunch of people toward 100% BEVs.

 

[Tommy G]

12V battery will charge if HVB has more than something like 15% whether car’s plugged in to charge or not, battery management sees to that.

I’d charge to 80% and just forget it

This is my thinking as well.

 

[E90alex]

12V battery will charge if HVB has more than something like 15% whether car’s plugged in to charge or not, battery management sees to that.

I’d charge to 80% and just forget it

80% is not recommended for storage, especially in high heat environments.

That’s not to say the battery will immediately fail if you do so, but it’s not as good for it as 50% or less if possible.

 

[DesertRat46]

I just bought a new left over 2025 in April. It had been at the dealer for five months. They only charged it the day I bought it. Only put in 15 KWH which brought it to 80 %.

 

[Ruthie B]

I think this is the perfect opportunity to leave your Mustang parked and unplugged at 50 -60 % and see what's left when you return in Oct.
I guess the Ford app can keep you updated from 3 states away ?
Enjoy your summer in the NC mountains !

 

[RickMachE]

I think this is the perfect opportunity to leave your Mustang parked and unplugged at 50 -60 % and see what's left when you return in Oct.
I guess the Ford app can keep you updated from 3 states away ?
Enjoy your summer in the NC mountains !

No. Vehicle goes to sleep. And prior to that, everything you use the app to check, you wake up the car, using the 12v...

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