How will I know when the 12 volt battery needs replacement?

[Ev Blau]

Same is true for an ICE car. Eventually the 12V will be dead and you’ll need a jump. I would familiarize yourself with the procedure to pop the frunk through the bumper access panel. And then learn how to remove the panels to get access to the 12V. Or even drill the access holes to get at the 12v connection points without removing panels. It will make a jump start that much easier.

Bought our low mileage ‘22 Select, RWD, no extended battery in Feb ‘23. Still has low mileage after a year (we’re retired and don’t drive long road trips). Bought with an extended dealer warranty.

If we can find someone reputable to drill access holes, will that void our warranty? How do we go about finding service to even do this? Thanks, nervous mom, owner of Red Hot

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[RickMachE]

Bought our low mileage ‘22 Select, RWD, no extended battery in Feb ‘23. Still has low mileage after a year (we’re retired and don’t drive long road trips). Bought with an extended dealer warranty.

If we can find someone reputable to drill access holes, will that void our warranty? How do we go about finding service to even do this? Thanks, nervous mom, owner of Red Hot

Cutting holes in the plastic lid, and then inserting covers into them, has zero impact on warranty.

Why do it? Are YOU going to charge or jump the battery?

 

[Teslaeata]

Your battery is fine. You‘re unlikely to ever see 100%.

This /\ /\ /\

There’s a perfectly good battery management system, worry ye not!

The more you worry about it spoils your enjoyment of the Stang, the more you’re talked into messing around with 12v battery, reconditioning, trickle charging etc etc the more chance you’ll bring about its premature demise or screw something else up……….IMO.

 

[Ev Blau]

Cutting holes in the plastic lid, and then inserting covers into them, has zero impact on warranty.

Why do it? Are YOU going to charge or jump the battery?

Just running “What if” scenarios through my head - especially since AAA didn’t ever show up the time my hubby called for flat tire service along a sketchy road. I frequently drive alone (can probably change a tire in an emergency if I have the strength to unscrew the lug nuts) but I would likely rely on someone to jump the battery.

 

[RickMachE]

Just running “What if” scenarios through my head - especially since AAA didn’t ever show up the time my hubby called for flat tire service along a sketchy road. I frequently drive alone (can probably change a tire in an emergency if I have the strength to unscrew the lug nuts) but I would likely rely on someone to jump the battery.

No spare as you know.

12v if it dies is simply under a panel. Have to remove center panel, then side panel. For the "it might" I would not do it. I did it to use my trickle charger.

 

[Logal727]

There’s currently a bug with some sort of 12v drain happening so some folks may be seeing the low 12v symptoms more frequently lately, which doesn’t necessarily mean the 12v is bad.

 

[Ev Blau]

No spare as you know.

12v if it dies is simply under a panel. Have to remove center panel, then side panel. For the "it might" I would not do it. I did it to use my trickle charger.

Rick, Thanks for your input. Always looking at Plan B’s, even if never implemented. The tire issue was for our Q5, not the MME.

Love the ‘Stang (my first was a ‘65 blue pony convertible bought in 1970) but I do get a teensie bit nervous these days about being stranded, for any reason.

 

[dml105]

Your battery is fine. You‘re unlikely to ever see 100%.

But I thought a long drive was supposed to raise the 12v voltage. Having driven an hour and a half today (a second time), my batter now sits at 73%.
Normal?

 

[Fremont Kid]

I was inquiring since I have an Interstate distributor by me, so I was wondering if it does show up as borderline to be replaced I could then just exchange it and be done, rather then go home remove, drive back, swap out and drive home and replace since I bought the car in May 2021

This is actually a good plan. I have found Interstate dealers have always been professional and done what is best for customer.

 

[Homestead]

But I thought a long drive was supposed to raise the 12v voltage. Having driven an hour and a half today (a second time), my batter now sits at 73%.
Normal?

For comparison I charged to 100% this morning and then drove 1 hour. Just checked and 12V battery is at 89%. Car/battery is 2 months old.

 

[JSW]

Replacing the 12v on your own is a PITA.
In my view, this alone makes it different than the above references to a 12v in an ICE vehicle (it is not an EZPZ task when it dies). My thoughts:

1. ICE vehicles don‘t lock you out when the 12v goes bad.
2. You cannot easily swap out the MMe 12v. To remove the 12v, you have to remove way more than just remove the FRUNK trim panels, and will likely need dealer intervention.
3. Getting stranded in the MMe is more arduous than an ICE vehicle (jump the FRUNK, remove panels, etc.)

In my view, if you do not frequently drive your MMe (especially when it’s cold), it’s worth considering a battery tender. The MMe will not intervene to charge the 12v until its charge drops to an unacceptably low level (again my opinion) and repeated cycles of this are problematic for the 12v. I find it easier and more efficient than the suggestions of others (use an inefficient 120v charger to prolong the charging process, etc). It’s soooo easy to simply connect the battery tender to the pigtail in the MMe.

I just prophylacticly replaced my 12v after 3 years because it outweighed the risk of getting stuck in the cold again at an inopportune time (like most folks, if I’m out in the cold it’s only because I’ve got things to do…places to be). I also acknowledge I’m more risk averse about getting inconvenienced in the cold than most people.

 

[apwelsh]

Does anyone know, if there is any thing preventing the use of a LiFePo4 battery? Lead Acid is only 10% usable before voltage drops too low. AGM is 20% usable before voltage drops too low. LiFe is 90% usable. In our RVs we replace the Lead Acid batteries with AGM to double battery life between charges, and now that AGM or standard in RVs we replace them with LiFePO4 because they are not a fire hazard like LiFe and have better BMS, so we can get 4.5x more battery life compared to AGM or 9x battery life compared to Lead Acid.

Seems since we don't have an engine to start, these cars should have an LiFePO4 deep cycle battery. any thoughts?

 

[Stanmckinney]

Is there some safe modification or some way to easily access 12 volt posts for a battery tender?

 

[Mach-Lee]

But I thought a long drive was supposed to raise the 12v voltage. Having driven an hour and a half today (a second time), my batter now sits at 73%.
Normal?

12V charging can be extremely slow if the battery is cold. I'm also not sure if you checked the 12V immediately after driving or not. So yes that could be normal depending on circumstances.

Does anyone know, if there is any thing preventing the use of a LiFePo4 battery? Lead Acid is only 10% usable before voltage drops too low. AGM is 20% usable before voltage drops too low. LiFe is 90% usable. In our RVs we replace the Lead Acid batteries with AGM to double battery life between charges, and now that AGM or standard in RVs we replace them with LiFePO4 because they are not a fire hazard like LiFe and have better BMS, so we can get 4.5x more battery life compared to AGM or 9x battery life compared to Lead Acid.

Seems since we don't have an engine to start, these cars should have an LiFePO4 deep cycle battery. any thoughts?

The short answer is NO, LFP is bad idea for replacement. See my 12V FAQ for why: 12V Battery FAQ

 

[HuntingPudel]

Is there some safe modification or some way to easily access 12 volt posts for a battery tender?

There are several safe methods. The cheapest is the two holes and furniture plug method. There is also the method @markboris used in placing a bulkhead connector inside the charge port. There's also the much more expensive route that I took (but it's really intended for doing FDRS updates, not trickle charging): ??

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