Leave plugged in?

[FloridaBreen]

A bit more detail, I was on vacation for 25 days. Having read the owners manual, I elected to not plug in, leaving hv battery at 61% (close to recommended 50%). When I returned home, truck was dead - no lights, no screen, drunk had to be manually opened. I measured 12v battery at it's terminals at 3.68 volts before connect my jump start battery, when I attached the positive, a small spark occured and the lights came on and I was able to activate the truck. I left it in run mode for 1.3 hours after removing the jump start.

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[Mal106]

That is the experience many here share. Interestingly, this is what the manual states:

A properly functioning truck should never completely drain the 12V battery unless you have something extra drawing power from it.

I think we are at a bit of an impass. The quote from the owner's manual does not specify truck on or off nor charging or not, or plugged in and finished charging. Anecdotal evidence says 12v charging is only with the truck on or actively charging and, from the manual, when the 12v is low.

As many times as the 12v has gotten low I can't help but think it can run down on its own if not on or actively charging even on a properly functioning truck.

I got an OTA 19 May that noted protection for the LVB. My likely failure was a couple days ago.

 

[carys98]

This is from the police modifiers bulletin. I don’t know if this applies to all Lightnings or just the SSV package but with all the reports of dead 12Vs it seems like it may not be working.

 

[Maquis]

This is from the police modifiers bulletin. I don’t know if this applies to all Lightnings or just the SSV package but with all the reports of dead 12Vs it seems like it may not be working.

I think that applies to all Ford EVs, and I read somewhere (maybe on the Mach-E forum) that the 40% threshold has been increased.

 

[Mache_Enrique]

Guys, was wondering what the school of thought is regarding your routines for charging. Seems most folks use the 80% rule or some charge to 90 pretty routinely, but I want to know if generally leaving the charger plugged in even after you reach the desired SOC is best for the battery?

Was told today by a Tesla owner that it’s best to leave them plugged in after you reach the desired charge and he gave me some scientific explanation why, but this could be the same argument as some of the oil threads I’ve read over the years.

I think all of your questions are answered via the uber smart folks on this thread. Just wanted to add a thank you for your service as law enforcement! Protecting your community is greatly appreciated!

 

[Robert1380]

I think all of your questions are answered via the uber smart folks on this thread. Just wanted to add a thank you for your service as law enforcement! Protecting your community is greatly appreciated!

Thanks. If I had it to do over I’d of been train engineer or a poet. Anything but a cop.

 

[chl]

Leaving the truck plugged in when the temp is going to go below 40F is a good idea.
It will use house energy to maintain the battery temperature.
I suppose it would also aid in running the cooling system when it is hot, but I am not sure.
If your truck will sit unused for an extended period of time, also leave plugged in to avoid a deep discharge of the HV battery.
However that won't prevent the 12V from being discharged unless the truck charges during that down time.
Energy is added to the 12V battery when charging, or when the truck is on, or when the low threshold is reached.
The on-board systems are always using some energy from the 12V unless it is disconnected (which leads to a hassle when reconnecting and having to re calibrate I read) even when the truck is "off."
Communications, timers, computer processes are still going on.

As for the Tesla recommendation, AI says:

"Many manufacturers, like Tesla, recommend keeping their vehicles plugged in to take advantage of the battery management system and avoid potential daily discharge"

whatever that means...

I did not have a significantly discharged 12V battery such that the truck would not boot up when I went away for two months in 2024 - not plugged in not charging just sitting at approx. 50% HV SOC.

I did have an issue with my 2012 Leaf under those circumstances however, because the 12V battery was running the computer timer programs...now I keep the Leaf on a trickle charger.

I recharge my truck to 80% whenever the SOC gets to no lower than 40% usually only once a week, because some experts say to avoid discharging more than 50% of your battery's capacity at a time, e.g, from 80% to below 30%, for longevity.

My low mileage 2012 Leaf is now almost 14 years old and still has over 80% capacity, most of the loss being due to age (1% to 2% per year is the norm). Still useful for local trips to the store and back - I no longer commute.

The rate of capacity loss is steeper in the beginning due to chemistry in the battery affecting the electrodes more at the beginning (a rough explanation), then it slows to a slower steady pace thereafter.

Bottom line I think is: Leaving it plugged in all the time won't hurt, but unless charging, or the temps are extreme it won't help anything either.

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