12v battery - difference between charging and maintaining?

Scooby24

Well-Known Member
First Name
Greg
Joined
Jul 2, 2021
Threads
24
Messages
1,897
Reaction score
2,871
Location
Olathe, KS
Vehicles
'21 MME-GT Star White; '22 MME Prem AWD DGM
Occupation
Perioperative Revenue Manager
Country flag
I'm not well versed in Lead Acid/AGM batteries. I bought a Noco Genius1 charger/maintainer as I saw voltage was low in my M40i (11.4). It charged overnight and was full by morning.

I was showing a healthy voltage on the GT at 12.8 but I figured I'd throw the Noco at it since I've seen several other GTs already indicated their 12v was either dead on delivery or has died shortly after.

It's charged overnight and it's still charging this morning. I suspect it was relatively low in charge. So if the HVB maintains the 12v...what's the difference between maintaining and charging?

Were 12v's not charged before installed? Were they just drained during transport? Does the "maintenance" the car does with the 12v not increase the state of charge of the 12v? Help me understand if you do please.

edit: Just finished charging so roughly 13-14 hours of charging at 1amp....so assuming 13-14ah and the battery is 35ah so I'm estimating that would mean the battery was at roughly 60% state of charge.

Yikes.
Sponsored

 
Last edited:

ShadowCVL

Well-Known Member
First Name
Chris
Joined
Jul 26, 2021
Threads
12
Messages
216
Reaction score
133
Location
40601
Vehicles
Jeep Grand Cherokee, GMC Sierra, MME Premium
Occupation
IT and Electronics
Country flag
I'm not well versed in Lead Acid/AGM batteries. I bought a Noco Genius1 charger/maintainer as I saw voltage was low in my M40i (11.4). It charged overnight and was full by morning.

I was showing a healthy voltage on the GT at 12.8 but I figured I'd throw the Noco at it since I've seen several other GTs already indicated their 12v was either dead on delivery or has died shortly after.

It's charged overnight and it's still charging this morning. I suspect it was relatively low in charge. So if the HVB maintains the 12v...what's the difference between maintaining and charging?

Were 12v's not charged before installed? Were they just drained during transport? Does the "maintenance" the car does with the 12v not increase the state of charge of the 12v? Help me understand if you do please.

edit: Just finished charging so roughly 13-14 hours of charging at 1amp....so assuming 13-14ah and the battery is 35ah so I'm estimating that would mean the battery was at roughly 60% state of charge.

Yikes.
I dont have a GT, Premium ER AWD here, did you pull the panel and charge the battery or is there another way I dont know of? I ask because I am now questioning the charge level of my battery, Ive had it a few months now though so its probably OK, but I also had to charge my mower 2 weeks ago cause for some reason it was almost flat.
 
OP
OP
Scooby24

Scooby24

Well-Known Member
First Name
Greg
Joined
Jul 2, 2021
Threads
24
Messages
1,897
Reaction score
2,871
Location
Olathe, KS
Vehicles
'21 MME-GT Star White; '22 MME Prem AWD DGM
Occupation
Perioperative Revenue Manager
Country flag
I dont have a GT, Premium ER AWD here, did you pull the panel and charge the battery or is there another way I dont know of? I ask because I am now questioning the charge level of my battery, Ive had it a few months now though so its probably OK, but I also had to charge my mower 2 weeks ago cause for some reason it was almost flat.
You just pull two plastic cowls. Takes about 2 minutes taking your time to not lose the clips. From there you charge via the dedicated power and ground lugs.

The charger needs to be "smart" and capable of charging an AGM at 12v.
 

dtbaker61

Well-Known Member
First Name
Dan
Joined
May 11, 2020
Threads
104
Messages
3,974
Reaction score
3,646
Location
santa fe,nm
Website
www.envirokarma.org
Vehicles
MME (delivered 2/26/21), DIY eMiata BEV
Occupation
Solar Sales/install
Country flag
I'm not well versed in Lead Acid/AGM batteries. I bought a Noco Genius1 charger/maintainer as I saw voltage was low in my M40i (11.4). It charged overnight and was full by morning.

I was showing a healthy voltage on the GT at 12.8 but I figured I'd throw the Noco at it since I've seen several other GTs already indicated their 12v was either dead on delivery or has died shortly after.

It's charged overnight and it's still charging this morning. I suspect it was relatively low in charge. So if the HVB maintains the 12v...what's the difference between maintaining and charging?

Were 12v's not charged before installed? Were they just drained during transport? Does the "maintenance" the car does with the 12v not increase the state of charge of the 12v? Help me understand if you do please.

edit: Just finished charging so roughly 13-14 hours of charging at 1amp....so assuming 13-14ah and the battery is 35ah so I'm estimating that would mean the battery was at roughly 60% state of charge.

Yikes.
You should not have to charge or maintain the 12v battery..... the MME supplies it with 14.4 and should charge it up when you are driving around, sort of like an ICE alternator; and the MME is supposed to 'check' the LVB even when 'off and sleeping', and maintain the LVB if needed.

If the LVB is NOT at 12.6-12.8 when the MME is off, the something is wrong with the on-board systems and you should have dealer make sure all modules and appropriate software updates have been applied.
 

ShadowCVL

Well-Known Member
First Name
Chris
Joined
Jul 26, 2021
Threads
12
Messages
216
Reaction score
133
Location
40601
Vehicles
Jeep Grand Cherokee, GMC Sierra, MME Premium
Occupation
IT and Electronics
Country flag
You just pull two plastic cowls. Takes about 2 minutes taking your time to not lose the clips. From there you charge via the dedicated power and ground lugs.

The charger needs to be "smart" and capable of charging an AGM at 12v.
thats what I thought, I have pulled those cowels.... and lost a clip down in the bay... that was fun to fish out with some bluetack and a ratchet extender....

I do have a "intelligent" charger, dont remember the brand, but its designed for LA and AGM, I bought it for my mower and my truck back when I wasnt driving but once a month.
 


OP
OP
Scooby24

Scooby24

Well-Known Member
First Name
Greg
Joined
Jul 2, 2021
Threads
24
Messages
1,897
Reaction score
2,871
Location
Olathe, KS
Vehicles
'21 MME-GT Star White; '22 MME Prem AWD DGM
Occupation
Perioperative Revenue Manager
Country flag
You should not have to charge or maintain the 12v battery..... the MME supplies it with 14.4 and should charge it up when you are driving around, sort of like an ICE alternator; and the MME is supposed to 'check' the LVB even when 'off and sleeping', and maintain the LVB if needed.

If the LVB is NOT at 12.6-12.8 when the MME is off, the something is wrong with the on-board systems and you should have dealer make sure all modules and appropriate software updates have been applied.
Understood, but "should not" and "do not" aren't necessarily synonymous here. We've had some GT's getting delivered with a dead 12v that needed charged...and @harrysiii just reported he had his 12v go dead.

Mine being at ~60% SoC and taking 14 ah of juice seems concerning, does it not?
 

TheVirtualTim

Well-Known Member
First Name
Tim
Joined
Oct 11, 2020
Threads
26
Messages
1,211
Reaction score
2,184
Location
Dearborn, MI
Vehicles
Mach-E First Edition, Escape Hybrid
Country flag
The high-voltage battery maintains the 12v when the car is not plugged in. The EVSE maintains the 12v battery when the car is plugged in. You shouldn't need to put a charger on it.

If for some reason the 12v were allowed to get low, you'll need a proper AGM battery charger (something that can put out 10 amps or better). Don't use a trickle charger. When my Mach-E had the 12v software bug, I put it on a 4 amp AGM trickle charger/maintainer and that wasn't nearly enough. Once I swapped it out for my 10-15 amp AGM charger the car was immediately happy and took on a proper charge.
 

harrysiii

Well-Known Member
First Name
Harry
Joined
May 13, 2020
Threads
15
Messages
596
Reaction score
618
Location
New Hampshire
Vehicles
'21 MME GTPE DMG; '18 Pacifica Limited
Country flag
Understood, but "should not" and "do not" aren't necessarily synonymous here. We've had some GT's getting delivered with a dead 12v that needed charged...and @harrysiii just reported he had his 12v go dead.

Mine being at ~60% SoC and taking 14 ah of juice seems concerning, does it not?
I asked the rep at the dealer if they notice my battery to be dead too and he quickly said "nope." I'm not confident in that answer since my AGM charger was showing it dead/extremely low. I did not, however, put my multimeter on it to check. I can say that it's been working fine since after they gave me my module updates yesterday.
 

Motomax

Well-Known Member
First Name
Max
Joined
Jul 19, 2021
Threads
4
Messages
971
Reaction score
984
Location
California
Vehicles
VW GLI, 4Runner
Country flag
The high-voltage battery maintains the 12v when the car is not plugged in. The EVSE maintains the 12v battery when the car is plugged in. You shouldn't need to put a charger on it.

If for some reason the 12v were allowed to get low, you'll need a proper AGM battery charger (something that can put out 10 amps or better). Don't use a trickle charger. When my Mach-E had the 12v software bug, I put it on a 4 amp AGM trickle charger/maintainer and that wasn't nearly enough. Once I swapped it out for my 10-15 amp AGM charger the car was immediately happy and took on a proper charge.
Trickle charger is perfectly fine to use, it’ll just take much longer to charge. I’ve used a motorcycle trickle charger to top off a car battery before when that’s all I had.
if your looking to immediately “jump” the car, obviously you’ll need more amps to trigger all the necessary systems.
 

TheVirtualTim

Well-Known Member
First Name
Tim
Joined
Oct 11, 2020
Threads
26
Messages
1,211
Reaction score
2,184
Location
Dearborn, MI
Vehicles
Mach-E First Edition, Escape Hybrid
Country flag
Trickle charger is perfectly fine to use, it’ll just take much longer to charge. I’ve used a motorcycle trickle charger to top off a car battery before when that’s all I had.
if your looking to immediately “jump” the car, obviously you’ll need more amps to trigger all the necessary systems.
When the 12v went low and I applied the 4 amp charger ... the car kept "trying" to wake up but it wasn't enough power. Crazy things were happening, lights were flickering all over the car, etc. When I finally applied a 10 amp charger, it all stopped and the car immediately stabilized.
 

Motomax

Well-Known Member
First Name
Max
Joined
Jul 19, 2021
Threads
4
Messages
971
Reaction score
984
Location
California
Vehicles
VW GLI, 4Runner
Country flag
When the 12v went low and I applied the 4 amp charger ... the car kept "trying" to wake up but it wasn't enough power. Crazy things were happening, lights were flickering all over the car, etc. When I finally applied a 10 amp charger, it all stopped and the car immediately stabilized.
Fair enough, most non-EVs don’t have the ability to turn themselves on and try to run off the charger.
Worst case is you disconnect one of the battery leads until you can get a decent charge. Obviously not ideal but if it’s all you have.
 

Mach-Lee

Well-Known Member
First Name
Lee
Joined
Jul 16, 2021
Threads
203
Messages
7,730
Reaction score
15,307
Location
Wisconsin
Vehicles
2022 Mach-E Premium AWD
Occupation
Sci/Eng
Country flag
To save energy, the system voltage may only be held around 13.2-13.8V to maintain the battery rather than charge it. This is why you'll notice the battery isn't fully charged, or see the messages regarding it. When the BMS thinks the battery is too low, it will switch to a higher voltage in the 14-15V range to actually charge up the battery to a higher SoC. Again, this is done to save energy and also prolong the life of the AGM. Seems like the Ford BMS targets about 70-80% SoC on the 12V batteries from what I've seen.

Fully charging your 12V battery overnight after delivery isn't a bad idea, I'd recommend that as well. It's probably been sitting at a low SoC for a while during transport, and probably has some internal sulfation built up. Putting it on an AGM charger and letting it maintain for 24-48 hours should mostly clear that up and restore most of the capacity.

But once you've fully charged the battery per the above, it should take care of itself. If it gets low or dies again, the battery is bad or the car has a software issue that should be corrected. A marginal battery will cause some issues due to the lack of capacity. It needs to power modules for long enough in between DC/DC wakeup events during certain conditions like sleep. Trickle charging is just a Band-Aid for the real problem of a failed 12V battery, so if it has issues send it to the dealer so you can get a new battery and not worry about it.

Per Tim here, if the car is completely dead you should jump start it or put it on a really big charger to avoid boot looping the modules when the voltage is right at threshold. It's sort of a Catch 22 situation where you need enough charge so the modules can go to sleep before getting anywhere with the battery.
 
OP
OP
Scooby24

Scooby24

Well-Known Member
First Name
Greg
Joined
Jul 2, 2021
Threads
24
Messages
1,897
Reaction score
2,871
Location
Olathe, KS
Vehicles
'21 MME-GT Star White; '22 MME Prem AWD DGM
Occupation
Perioperative Revenue Manager
Country flag
To save energy, the system voltage may only be held around 13.2-13.8V to maintain the battery rather than charge it. This is why you'll notice the battery isn't fully charged, or see the messages regarding it. When the BMS thinks the battery is too low, it will switch to a higher voltage in the 14-15V range to actually charge up the battery to a higher SoC. Again, this is done to save energy and also prolong the life of the AGM. Seems like the Ford BMS targets about 70-80% SoC on the 12V batteries from what I've seen.

Fully charging your 12V battery overnight after delivery isn't a bad idea, I'd recommend that as well. It's probably been sitting at a low SoC for a while during transport, and probably has some internal sulfation built up. Putting it on an AGM charger and letting it maintain for 24-48 hours should mostly clear that up and restore most of the capacity.

But once you've fully charged the battery per the above, it should take care of itself. If it gets low or dies again, the battery is bad or the car has a software issue that should be corrected. A marginal battery will cause some issues due to the lack of capacity. It needs to power modules for long enough in between DC/DC wakeup events during certain conditions like sleep. Trickle charging is just a Band-Aid for the real problem of a failed 12V battery, so if it has issues send it to the dealer so you can get a new battery and not worry about it.

Per Tim here, if the car is completely dead you should jump start it or put it on a really big charger to avoid boot looping the modules when the voltage is right at threshold. It's sort of a Catch 22 situation where you need enough charge so the modules can go to sleep before getting anywhere with the battery.
This is great information and exactly what I was hoping to gather. Thank you!
 

Bullitt_&_MME

Well-Known Member
First Name
Andrew
Joined
Sep 30, 2021
Threads
5
Messages
88
Reaction score
49
Location
Cleveland, OH
Vehicles
2001 Bullitt; 2018 Expedition Max Limited
Occupation
Logistics
Country flag
Understood, but "should not" and "do not" aren't necessarily synonymous here. We've had some GT's getting delivered with a dead 12v that needed charged...and @harrysiii just reported he had his 12v go dead.

Mine being at ~60% SoC and taking 14 ah of juice seems concerning, does it not?
yep my GT just arrived dead today. Anything else to do out there besides charging the heck out of the 12V and charging the MME up to it's highest levels too?

Mine arrived today w/ a dead 12v and <17 miles left on the range...
 

bshaw

Well-Known Member
Joined
May 18, 2020
Threads
12
Messages
1,280
Reaction score
1,709
Location
Boston, MA
Vehicles
2021 Mustang Mach E 4X (Job 1)
Country flag
yep my GT just arrived dead today. Anything else to do out there besides charging the heck out of the 12V and charging the MME up to it's highest levels too?

Mine arrived today w/ a dead 12v and <17 miles left on the range...
The low range is why your 12V battery was not charged. I believe once the HVB goes below a certain level, it won't run the DC-DC converter any longer to try and keep the 12V charged up.

Your 12V may be fine, if you are able to charge it externally, and then get on a L2 charger for the HVB.

Your dealer delivered the car to you in this condition?
Sponsored

 
 




Top