Plug in to Maintain 12V Battery

[mkhuffman]

@Mach-Lee could you help me reconcile these two statements? It seems in the first message that the car will maintain the LVB as long as the HVB isn’t low. But in the second message that it will only maintain while charging.

While charging and while the car is on, it will maintain the LVB at 92-94%, from what I have measured. When the car is off and not charging, when the SOC hits 40%, the car will recharge the battery. It is not healthy for the LVB to get down to 40% on a regular basis, and really that is unusual. As Lee said, it could happen if you rarely drive the car. It definitely happens if you have a 12V device connected that is draining the battery.

IMO if the LVB regularly drops below 80%, it is going to wear out sooner than if you can keep it above 90%. If you can't drive it and you don't want to turn the car on to charge the LVB, get a battery tender. It is common sense maintenance needed for a car that isn't driven often, ICE or BEV.

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[Triggerhappy007]

With daily use, your 12v battery should have no issues. The only thing that might affect it could be accessories such as improperly installed dashcams, or leaving things plugged in to the "cigarettte" lighter.

Doesn't the 12V outlet automatically shut off after a few minutes? Isn't that a good enough safeguard?

 

[RandyMache]

While charging and while the car is on, it will maintain the LVB at 92-94%, from what I have measured. When the car is off and not charging, when the SOC hits 40%, the car will recharge the battery. It is not healthy for the LVB to get down to 40% on a regular basis, and really that is unusual. As Lee said, it could happen if you rarely drive the car. It definitely happens if you have a 12V device connected that is draining the battery.

IMO if the LVB regularly drops below 80%, it is going to wear out sooner than if you can keep it above 90%. If you can't drive it and you don't want to turn the car on to charge the LVB, get a battery tender. It is common sense maintenance needed for a car that isn't driven often, ICE or BEV.

Are you sure the HVB won’t keep the 12v battery at a nearly full state of charge nearly all the time? You’re right about lead batteries. An ICE vehicle will constantly keep the 12v battery at a full state. Seems weird if the MME dosen't do the same….. but I don’t know….. I’m just asking…..

 

[Mach1E]

While charging and while the car is on, it will maintain the LVB at 92-94%, from what I have measured. When the car is off and not charging, when the SOC hits 40%, the car will recharge the battery. It is not healthy for the LVB to get down to 40% on a regular basis, and really that is unusual. As Lee said, it could happen if you rarely drive the car. It definitely happens if you have a 12V device connected that is draining the battery.

IMO if the LVB regularly drops below 80%, it is going to wear out sooner than if you can keep it above 90%. If you can't drive it and you don't want to turn the car on to charge the LVB, get a battery tender. It is common sense maintenance needed for a car that isn't driven often, ICE or BEV.

This is what I would expect, which is why I’m wondering why my battery has been dropping lately when I’m driving every day and charging every couple days.

Some say “don’t worry, car should take car of it,” but I’ve read too many threads about people getting towed from a dead LVB I think.

12v batteries never seem to last more than a few years in Florida anyways.

 

[mkhuffman]

Are you sure the HVB won’t keep the 12v battery at a nearly full state of charge nearly all the time? You’re right about lead batteries. An ICE vehicle will constantly keep the 12v battery at a full state. Seems weird if the MME dosen't do the same….. but I don’t know….. I’m just asking…..

It does when the car is on and when it is charging, which is similar to how a ICE vehicle maintains the 12V battery. It does not keep the 12V battery at "full state" when the car is off.

I don't think you want it to anyway, because then it could cause the HVB to lose charge. Ford did a good job keeping HVB vampire drain at practically zero while still protecting the LVB. Not maintaining it, but protecting it from discharging completely.

 

[RandyMache]

This is what I would expect, which is why I’m wondering why my battery has been dropping lately when I’m driving every day and charging every couple days.

Some say “don’t worry, car should take car of it,” but I’ve read too many threads about people getting towed from a dead LVB I think.

12v batteries never seem to last more than a few years in Florida anyways.

I think we are talking about 12v batteries here and not EV 12v batteries. So other than the battery being a little smaller at 330 cca, which some small cars actually use, it is the same battery whether in An EV or ICE. My experience with Ford is that 8 out of 10 new Ford cars I’ve bought over the years, almost always the battery never went past 2 years. Upon replacement, even at Ford, the batteries went on to last 5+ years. So, I don’t know if they put inferior batteries at the factory, or they are using old [but new] batteries sitting in storage or what. But the bottom line is that if you’re driving a 2021 or even an early 2022 MME, your battery could be going out. If the battery is not holding power and the charging system is ok, then replace it under warranty. Or just replace it yourself.

 

[Triggerhappy007]

This is what I would expect, which is why I’m wondering why my battery has been dropping lately when I’m driving every day and charging every couple days.

Some say “don’t worry, car should take car of it,” but I’ve read too many threads about people getting towed from a dead LVB I think.

12v batteries never seem to last more than a few years in Florida anyways.

I'm worried too because I live in a hot state and had bad experiences in the past with 12V batteries failing prematurely. The battery on my 15 Focus EV lasted 1.5 years, my 19 Leaf lasted a year. Someone on the Leaf forum from Arizona said an AGM battery in their Leaf lasts about 4 years compared to 1-1/2 years for a Lead acid battery. I have an AGM battery in my Pacifica Hybrid and it's just over 3 years old but it doesn't sit in the sun like my Mach-E.

 

[RandyMache]

I'm worried too because I live in a hot state and had bad experiences in the past with 12V batteries failing prematurely. The battery on my 15 Focus EV lasted 1.5 years, my 19 Leaf lasted a year. Someone on the Leaf forum from Arizona said an AGM battery in their Leaf lasts about 4 years compared to 1-1/2 years for a Lead acid battery. I have an AGM battery in my Pacifica Hybrid and it's just over 3 years old but it doesn't sit in the sun like my Mach-E.

All 12v car batteries should last 4+ years, period. When they don’t, it’s caused by the vehicle or the battery itself. I grew up in Minnesota and in my day it got frick’en cold in the winter and super hot in the summer. Back in the 1970’s and 80’s, batteries lasted 5+ years no problem. Replacement batteries lasted no problem. I’ve only had ”factory” batteries die prematurely in my experience.

 

[Rj786]

JL is correct. I don’t drive as much either and do short trips under 30km(~18miles) two or three times a week plus once month 200km(120 miles) trip to Toronto. I have never seen this message Because Car is always plugged in when it is in the garage, charging is set at 90% during off peak hours.
2022 Premium ER 11k km(6600 miles) in 12 months.

 

[Mach-Lee]

@Mach-Lee could you help me reconcile these two statements? It seems in the first message that the car will maintain the LVB as long as the HVB isn’t low. But in the second message that it will only maintain while charging.

Well that depends on your definition of "maintain". Does maintain mean prevent from dying, or maintain in a healthy voltage range that promotes battery longevity?

The car will automatically recharge the battery when it gets all the way down to 40% so it doesn't go completely dead, but these recharge events are stressful on the battery. As Ford's bulletin states, you don't want this recharge event happening daily because it will wear out the battery quickly.

With normal driving and charging, the 12V battery should stay in the 70-95% range, which is healthy. If you want the AGM battery to last the longest, you want to keep it in this higher range and avoid discharging below 50%. The charging system is only active when the car is on or charging, so if the car is parked for a long time the battery will slowly drain down.

My advice is to ignore the "plug in to maintain 12V battery" message the first time, but if it keeps occurring multiple times it does mean you have a situation that is putting excessive stress on the 12V battery. Either you have some kind of 12V drain occurring, or your 12V battery is becoming marginal and needs reconditioning or replacement.

I want to remind everyone that draining a lead acid battery below 50% is bad for it. The longer the battery spends at a low state of charge, the more sulfation buildup it will have, and the harder it will be to fully remove the sulfation with charging. For maximum longevity, always keep the battery above 80% SoC.

I think we are talking about 12v batteries here and not EV 12v batteries. So other than the battery being a little smaller at 330 cca, which some small cars actually use, it is the same battery whether in An EV or ICE. My experience with Ford is that 8 out of 10 new Ford cars I’ve bought over the years, almost always the battery never went past 2 years. Upon replacement, even at Ford, the batteries went on to last 5+ years. So, I don’t know if they put inferior batteries at the factory, or they are using old [but new] batteries sitting in storage or what. But the bottom line is that if you’re driving a 2021 or even an early 2022 MME, your battery could be going out. If the battery is not holding power and the charging system is ok, then replace it under warranty. Or just replace it yourself.

Ford does use good batteries. I've just replaced a couple originals that lasted 7 years. I personally only buy Ford Max batteries because I've always had good luck with them. Heat kills batteries, so in California 5 years is probably the most you can get out of one. If the vehicle was parked for a long time on a dealer lot before sale, that can damage the battery from sitting at a low SoC and not being driven. This is why I recommend reconditioning batteries in new vehicles to remove sulfation from sitting unused.

All 12v car batteries should last 4+ years, period. When they don’t, it’s caused by the vehicle or the battery itself. I grew up in Minnesota and in my day it got frick’en cold in the winter and super hot in the summer. Back in the 1970’s and 80’s, batteries lasted 5+ years no problem. Replacement batteries lasted no problem. I’ve only had ”factory” batteries die prematurely in my experience.

Again, battery lifespan depends on the temperature it's exposed to, heat kills them faster:

In Minnesota 5 years is typical, but where you live now they will only last about 3 years because of the heat.

 

[mkhuffman]

If the vehicle was parked for a long time on a dealer lot before sale, that can damage the battery from sitting at a low SoC and not being driven. This is why I recommend reconditioning batteries in new vehicles to remove sulfation from sitting unused.

@RandyMache, this is why I think you have had problems with new car batteries. Not only do cars sit on the lot without being driven, the salespeople will open the doors, open the truck, etc. which runs down the 12V battery. I remember one time I was looking at a car and they mentioned they had to recharge the 12V battery because of that.

I didn't know about the reconditioning procedure until I read Lee's thread about how to do it. I expect many people don't know about it either, and they just think the battery died because it was bad from the factory. I think it is much more likely the battery was damaged by sitting at a low state of charge for too long.

 

[RandyMache]

@RandyMache, this is why I think you have had problems with new car batteries. Not only do cars sit on the lot without being driven, the salespeople will open the doors, open the truck, etc. which runs down the 12V battery. I remember one time I was looking at a car and they mentioned they had to recharge the 12V battery because of that.

I didn't know about the reconditioning procedure until I read Lee's thread about how to do it. I expect many people don't know about it either, and they just think the battery died because it was bad from the factory. I think it is much more likely the battery was damaged by sitting at a low state of charge for too long.

Your mostly likely right. I didn’t always pay attention to the manufacturing date of the vehicle. I can say that my new MME was manufactured in July this year and I bought it September 30th. So in theory, I should have a pretty good 12v battery. Let’s see…….

 

[kodiakng]

I want to remind everyone that draining a lead acid battery below 50% is bad for it. The longer the battery spends at a low state of charge, the more sulfation buildup it will have, and the harder it will be to fully remove the sulfation with charging. For maximum longevity, always keep the battery above 80% SoC.

i'm curious why ford waits until the LVB gets down to 40% before initiating a charge from the HVB. 50% would seem to be a better floor value.

 

[Mach-Lee]

i'm curious why ford waits until the LVB gets down to 40% before initiating a charge from the HVB. 50% would seem to be a better floor value.

Agree. They were probably worried that setting the threshold higher would cause too many wake-up/recharge events, causing more cycles on the 12V battery and draining the HVB. The whole “avoid phantom drain” thing is viewed as a big deal in their engineering decisions.

Personally I would set it to recharge at 60% up to 90%. That would be better for the 12V, but would drain the HVB more often. Unlike the Ford engineers, it’s not a big deal to me if the HVB loses 1% a week from maintaining the 12V battery. I’d rather keep the 12V topped up than waiting for it to get all the way down to 40% before recharging.

 

[Teslaeata]

i'm curious why ford waits until the LVB gets down to 40% before initiating a charge from the HVB. 50% would seem to be a better floor value.

Because they know what they’re doing??‍

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