The stranded saga continues

[A-A-Ron]

Follow up from Mach E left us stranded

After taking it home, hooking the battery up to a tester/conditioner (it didn't fail on the tester) overnight and resetting the BCM after it was fully topped off - had no issues for 2 weeks. But the last two days, I've had low battery messages after leaving the car parked in front of my house in the afternoon.

Both days, it's charged to 90% overnight, no issues starting in the morning, 40 mi drive to work, park for 8 hours, drive 40 miles home. Leave it in the driveway for 30 minutes, turn it back on to head to the gym and Stop Safely pops up and it won't start. Plug the OBDII reader in and low battery messages abound. At some point yesterday, I turned it off and on and it turned on no problem. That was before I could find the 12v levels in CarScanner, so I'm not sure what it was showing prior, but it was reading 78% once I found it (after the car was on).

Today - same exact thing. This time, 12v was reading under 9v and the SOC quickly dropped from 48% to 38%. Turned it off and on a few times, and eventually it just started normally and immediately started charging the 12v. 10 minutes or so and it was back up over 70%.

So yeah - '21 MME, new 12v battery (December), doesn't seem to drain in 8hrs at work but drains in 30min back at home. No accessories plugged in, battery isn't faulting on my tester and seems to be charging as expected - it's like the car either isn't charging it on my drive home or it's draining quickly once I'm home. Any thoughts before I drag this in for service?

3FMTK3SU2MMA64628 if that helps

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[Mach-Lee]

If the voltage is only 9V, the SoC should be way less than 48%. So either something with the BMS is messed up, or you actually have the rare infant mortality of a 12V battery. Because the voltage is crashing so fast, the BMS isn’t able to trigger the automatic recharge in time before it completely dies.

Not sure if you have any way of testing the battery capacity, but I’d recommend you bring it back and have them test the battery again. You may need another new battery. And make sure the BMS is reset properly.

Can you verify the 12V battery age parameter in Car Scanner is properly showing the age as only a couple months (meaning it was properly reset)? It’s easy to mess up the timing during the reset procedure (the battery light won’t flash if improperly done).

Did somebody make sure your GWM, IPC, and BCM modules are updated to avoid drains?

 

[A-A-Ron]

If the voltage is only 9V, the SoC should be way less than 48%. So either something with the BMS is messed up, or you actually have the rare infant mortality of a 12V battery. Because the voltage is crashing so fast, the BMS isn’t able to trigger the automatic recharge in time before it completely dies.

Not sure if you have any way of testing the battery capacity, but I’d recommend you bring it back and have them test the battery again. You may need another new battery. And make sure the BMS is reset properly.

Can you verify the 12V battery age parameter in Car Scanner is properly showing the age as only a couple months (meaning it was properly reset)? It’s easy to mess up the timing during the reset procedure (the battery light won’t flash if improperly done).

Did somebody make sure your GWM, IPC, and BCM modules are updated to avoid drains?

I was worried the BMS wasn't reset properly in December so I reset it again 2 weeks ago after it died and I put it on a charger overnight. Figured at only 3 months and fully charged, it should be fine to reset again. I may try that again one more time - hook up the charger and let it go 12 hours, then reset the BMS. Just finished cutting access holes to the jump lugs because I'm tired of pulling panels in the frunk.

Tossing a jump pack in my bag, just in case it doesn't work, but willing to chance it one more time before I take it in.

 

[Mach-Lee]

I was worried the BMS wasn't reset properly in December so I reset it again 2 weeks ago after it died and I put it on a charger overnight. Figured at only 3 months and fully charged, it should be fine to reset again. I may try that again one more time - hook up the charger and let it go 12 hours, then reset the BMS. Just finished cutting access holes to the jump lugs because I'm tired of pulling panels in the frunk.

Tossing a jump pack in my bag, just in case it doesn't work, but willing to chance it one more time before I take it in.

Just use caution resetting the BMS on a potentially bad battery. That can cause it to die before recharge is triggered until it learns the capacity is lowered significantly. It's expecting the battery to be full capacity after the reset.

Unless you reset the BMS when it was low (instead of being fully charged) or have been charging it wrong (putting the battery charger on the negative battery terminal instead of the body ground), I don't think resetting the BMS again will help.

 

[A-A-Ron]

Just use caution resetting the BMS on a potentially bad battery. That can cause it to die before recharge is triggered until it learns the capacity is lowered significantly. It's expecting the battery to be full capacity after the reset.

Unless you reset the BMS when it was low (instead of being fully charged) or have been charging it wrong (putting the battery charger on the negative battery terminal instead of the body ground), I don't think resetting the BMS again will help.

Yeah, I didn't see your post and figured that out myself this morning.

So I ran the car last night for 1.5 hours (daughter had a dance class, I sat outside catching up on work), it was reporting 80% when I got home at 8. Plugged my battery charger/tender in and it said 77% and left it to charge. By 10 last night, it had topped off at 100% and I left it overnight on the minder. Came out this morning, disconnected the tender, did the BMS reset (probably shouldn't have but my thought was I wanted to do it right away knowing it'd been charged 10 hours overnight), turned the car on and... Stop Safely Now, Positrac errors, L2 charging fault, and no drive modes.

Plugged in the OBD - it's reading 9.7v (but 120% charge - so yeah, definitely resetting the BMS wasn't the best idea - also, no low voltage codes this time). A few attempts to turn it off and restart it didn't work, then I turned it off again and noticed the 12v level on Carscan was still reporting and was creeping up, got up to about 10.8 and stabilized, so I tried to start it again and poof - back on like nothing was wrong. 12v immediately started reporting 13.3v (likely with a boost from the HV).

So yeah - pretty sure the battery is junk. Going to pick up a new one on my way home tonight, let it charge overnight before installing it in the morning. Then I'll take this back for my core refund and see if they 'll honor any of the warranty on it.

 

[A-A-Ron]

@Mach-Lee - totally appreciate the help here (and the 12v FAQ)

 

[RickMachE]

Yeah, I didn't see your post and figured that out myself this morning.

So I ran the car last night for 1.5 hours (daughter had a dance class, I sat outside catching up on work), it was reporting 80% when I got home at 8. Plugged my battery charger/tender in and it said 77% and left it to charge. By 10 last night, it had topped off at 100% and I left it overnight on the minder. Came out this morning, disconnected the tender, did the BMS reset (probably shouldn't have but my thought was I wanted to do it right away knowing it'd been charged 10 hours overnight), turned the car on and... Stop Safely Now, Positrac errors, L2 charging fault, and no drive modes.

Plugged in the OBD - it's reading 9.7v (but 120% charge - so yeah, definitely resetting the BMS wasn't the best idea - also, no low voltage codes this time). A few attempts to turn it off and restart it didn't work, then I turned it off again and noticed the 12v level on Carscan was still reporting and was creeping up, got up to about 10.8 and stabilized, so I tried to start it again and poof - back on like nothing was wrong. 12v immediately started reporting 13.3v (likely with a boost from the HV).

So yeah - pretty sure the battery is junk. Going to pick up a new one on my way home tonight, let it charge overnight before installing it in the morning. Then I'll take this back for my core refund and see if they 'll honor any of the warranty on it.

You need to reverse the order. Bring old one to get warranty replacement on new one.

 

[A-A-Ron]

You need to reverse the order. Bring old one to get warranty replacement on new one.

That, unfortunately, would require another car

 

[RickMachE]

That, unfortunately, would require another car

I would make sure they understand you are going to make a warranty claim for the battery before you purchase.

 

[A-A-Ron]

I would make sure they understand you are going to make a warranty claim for the battery before you purchase.

I'll swing by on my way home and talk to them. If it's a problem, I can go home, pull the battery, walk the mile to my wife's work and snag her car - then go pick up the battery and swap it and drop it back off, return her car, walk the mile back home and finish. Assuming the storms are past.

At least she's fairly close - my office is 40 miles from the house - don't think I could make it work if this was reversed.

 

[JimmyMachE]

@A-A-Ron What is your Aux battery standby drain / Quiescent average in Car Scanner? It should not exceed -50 mA.

 

[A-A-Ron]

I would make sure they understand you are going to make a warranty claim for the battery before you purchase.

They require their service department to test and service it. It’s a 3 hour wait. Fml.

 

[A-A-Ron]

Also, told service tech we left it at the airport for a week and he told me “oh yeah, that’s too long, they die all the time even you leave it that long” which is both bullshit and sad

 

[A-A-Ron]

@A-A-Ron What is your Aux battery standby drain / Quiescent average in Car Scanner? It should not exceed -50 mA.

34mA

 

[A-A-Ron]

“Oh, it’s an EV, we’re going to need 1-3 days”

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