12V Battery Replacement

[MightyMike]

There are a lot of posts of people ending up with bricked MMEs when their 12V Battery dies. In my older (gas) cars, when the battery died, I'd just pop the hood, replace it and move on.

It feels like the MME is both more difficult to replace, and likely to die at unexpected times (like maybe away from home). Is it worth looking at replacing it prior to failure? Or is there a test that should be run to see if you are "close to failure."

Or am I just unnecessarily worried (I figure my 22 MME with 30k miles on it might be getting close?)

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[Snakebitten]

There can't possibly be anything wrong with replacing the battery before it fails.
As you described, with this particular vehicles, waiting until it fails is far riskier.

 

[Sikkun]

It’s not an ICE vs EV issue. Your 12v was never guaranteed to die in a convenient place/time.

It’s a bigger problem because of the decision to make the battery more annoying to access and remove the ability to mechanically open a door. But neither of those are EV requirements, just trying to be “cool”.

 

[AliRafiee]

It’s the same as a gas car. You know it’s dead when it won’t start the car and you replace at home or away from home. Same here.

 

[thenew3]

Are you saying 12V for ICE vehicles only die while they are at the owner's home/driveway/garage?

 

[alexgorod]

remove the ability to mechanically open a door

This.

I'm getting the new battery this week.

 

[markboris]

I've always replaced my 12V batteries at 3 years regardless of what shape they are in. I'm sure I've wasted quite a bit of money doing this over the last 50 years or so but I've also never been stuck anywhere with a dead battery. My Mach-E is three years old this month and I replaced the battery last month. I don't find it difficult at all to replace.

 

[JoeyD]

My car is 3 1/2 years old and I replaced the 12V battery last month also. Being subject to several months of very high summer heat we have here in AZ, the batteries don't seem to last as long so I replace them at around 3 years so I don't find myself stranded.

 

[RickMachE]

There can't possibly be anything wrong with replacing the battery before it fails.
As you described, with this particular vehicles, waiting until it fails is far riskier.

Sure there is.

Waste of money.
Waste of resources.

Get it load tested. Then every fall.

 

[Snakebitten]

That's a similar argument to oil change intervals.

I am draining oil that is still doing it's job of lubricating the engine. I wouldn't wait until it fails.

I plan on changing the battery while it still is providing 12V. Have no intention of waiting until it fails.

Obviously not everyone would agree with the approach. I've lived without consensus for nearly three quarters of a century. Nothing new about that. ?

Heck, driving a Mach-E certainly doesn't meet that bar.

 

[AliRafiee]

I've always replaced my 12V batteries at 3 years regardless of what shape they are in. I'm sure I've wasted quite a bit of money doing this over the last 50 years or so but I've also never been stuck anywhere with a dead battery. My MME is three years old this month and I replaced the battery last month. I don't find it difficult at all to replace.

I’m pretty sure my 2011 Mustang GT had the original battery when I sold it 10 years later. I don’t recall changing the battery on it. Same with my GTO that I had for 6 years. Before that I never kept a car more than a couple of years.

 

[markboris]

I don't know if load testing batteries helps much. I guess it does if a battery is showing signs of getting weak? I don't know much about batteries except they can suddenly fail. My dad has his 2007 Volvo XC-70 battery tested at Pep Boys about twice each year and it made no difference. His battery has died twice just like a light bulb. One minute working, next minute dead. Once was when my parents were up in Tahoe with friends at a remote cabin and the other time on Christmas Eve around midnight. That was a fun one. Both times the battery was around 5-6 years old. I know he's had batteries fail like that a few times when he was working (drove delivery trucks). He's very frugal and doesn't follow my advice to replace it when they are around 3 years old. I totally get that he doesn't want to spend money on something that is still working. I would rather spend the money and hopefully never have a sudden, inconvenient failure (which in 50+ years I haven't yet).

 

[thenew3]

I’m pretty sure my 2011 Mustang GT had the original battery when I sold it 10 years later. I don’t recall changing the battery on it. Same with my GTO that I had for 6 years. Before that I never kept a car more than a couple of years.

Your GT and GTO likely had fewer electronics that stay awake draining the battery 24x7 compared to the MME. Also those cars likely also had a 12V that's 2x the size/capacity of the tiny 12V in the MME.

 

[thenew3]

In older ICE vehicles there are usually signs that a battery is getting weak (slow/long crank for example) also a dead battery doesn't prevent you from getting into the car (there was a physical key you can use to unlock the door, and a mechanical door handle to open the door).

On these newer cars with only electronic keys (phone, nfc card etc) and electronic door actuators, a weak/dead 12v means you can't even get into the car.

On an EV, it's hard to tell if a 12V is getting weak since there's no cranking to start the car. So I can see why people are proactively replacing the 12V battery.

Also, older cars do not have a ton of electronics that stay awake 24x7 even when the car is off. Newer cars have computers that are always awake, thus constantly draining the 12v.

My wife's BMW X3 is on it's original battery after 9 years and it's still going strong. My BMW X7's battery was too weak to do any OTA updates last year at under 4 years old. It still starts the engine just fine, but the computer thinks the battery is too weak for it to complete OTA updates. Of course the X3 is much older and doesn't have a cellular connection or any kind of PAAK thus little to no power drain when the engine is off while the X7 is connected to 4G all the time and has paak.

Also temperature of the operating environment will affect a battery life span. When we used to live in Texas, our 12V would need replacement every 2-3 years due to the hot temps. Now that we're in a more mild climate (50-60 year round, occasionally 70-80 in summer). the 12'v batteries are lasting much longer, frequently over 10 years.

I have a 21 Job 1 that was built in December 2020, 12v still going strong in it.

 

[Teslaeata]

That's a similar argument to oil change intervals.

No it’s not, it really isn’t?

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