Plug in to Maintain 12V Battery

[Mr. Toejam]

With Carscanner, I would notice a 20%drop in state of charge of the 12 battery every night. I took it to my Dealer and they said my batter was definitely not holding a charge. They replaced it. I still noticed about a 4% drop overnight. So I canceled my Recurrent account and I saw 1 or 2% last night. He said this is the second 12v they have changed on a mach-e with less than 2 years ownership.
Hopefully it stays this way.

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[Teslaeata]

14.4V means the DC-DC converter was charging the 12v battery.

Both charts show open circuit /resting/ battery voltage - should be measured 12-24 hours after removing from the vehicle.

Fully charged AGM battery will reach 13V, a bit higher than normal lead acid battery.

Of course, you’re right, I should’ve spotted that?

Should have provide the SoC voltage which was just over 13V.

 

[PonyTail]

Turn the car on in your garage occasionally. It will shut off after 30 minutes and charge up the battery in that time.

Or you could get a battery maintainer.

Additionally I’d recommend disabling welcome lighting to reduce the battery drain.

This message is somewhat expected for a car that is barely driven, especially short trips.

I'm getting the message also but there's no way I'm giving up my mustang on the ground

 

[Mari76]

I get the dreaded 12V fault all the time too. Dealership has no clue why and says the battery is testing good.

And just today i got this new message that i had never seen before.

 

[mkhuffman]

Maybe you should plug in.

?

 

[Mari76]

Maybe you should plug in.

?

Plug in every day?! I've had my car for 2 years and this just started happening in June.

 

[Teslaeata]

Dealership has no clue why and says the battery is testing good.

Was just thinking the same as the dealer regarding these messages because they are counter to the way the DC/DC converter, which is effectively the HV/LV charger, actually functions.

Is this more likely to be false messaging, misreporting something which doesn’t actually exist?

 

[Blackpony]

I have a CTEK MXS 5.0 battery charger which has an AGM option. Can I use this to recondition my 12V battery?

 

[mkhuffman]

Plug in every day?! I've had my car for 2 years and this just started happening in June.

It seems like you need to recondition your LVB. I do it yearly.

 

[JimmyMachE]

Plug in every day?! I've had my car for 2 years and this just started happening in June.

Well, your dashcam on OBD2 port probably takes its toll:
https://www.macheforum.com/site/thr...n-option-which-one-to-pick.10066/#post-255789

https://www.macheforum.com/site/thr...on-which-one-to-pick.10066/page-2#post-255903

 

[Mach-Lee]

Well, your dashcam on OBD2 port probably takes its toll:
https://www.macheforum.com/site/thr...n-option-which-one-to-pick.10066/#post-255789

https://www.macheforum.com/site/thr...on-which-one-to-pick.10066/page-2#post-255903

I don't understand when people install an always-on dashcam and then can't figure out why they later receive 12V drain messages...

 

[George Knighton]

When I had the Chevy Bolt, the forum grey suits said that the car should remain plugged in all of the time, and that this kept the accessory battery properly conditioned, and I would notice the circulation system running occasionally to keep the drive battery conditioned.

So this is not true of the Ford, and there is no advantage staying plugged in when the car is at home?

For some reason this surprises me.

 

[Teslaeata]

This is very helpful thread. I have had 12V warnings in the past and the warning last week. My car is typically used for very short trips so sounds like the 12V charging issue could be the result

I feel sure the message is for information not warning or instruction.

We all need to distance our thoughts from those of the ICE-age man where driving=12V charging and ONLY driving=12V charging.

‘s not how an HV EV 12V charging system works at all.

BMS will command charging the 12V battery whether you’re driving, parked, parked & plugged in or not, that this message appears or not, so long as we keep our HV battery above a certain percentage which I have written somewhere before (was that 15%??‍ I don’t remember) we’re fine.

Overthinking spoils the enjoyment of these wonderful cars and attempting to manage something which is already managed is pointless.

 

[Teslaeata]

I don't understand when people install an always-on dashcam and then can't figure out why they later receive 12V drain messages...

Drain message?

 

[RickMachE]

When we had our Fusion Energi, we believed that it kept the 12v charged when plugged in. When we got the Mach-E, we believed the same, and that even unplugged it would keep the 12v charged if necessary, down to some low level for the high voltage battery.

It seems quite ridiculous that Ford doesn't have the 12v charge whenever feasible - not just driving, not just charging, but when plugged in, when unplugged, etc.

If they can put warnings on the HVB at certain levels, they can certainly charge the 12v AND inform the customer - "Your 12v battery is currently being charged by the high voltage battery, when not plugged in. Please unplug things that are doing this (not exact wording) so you don't drain the HVB".

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