Odd battery behavior - rapid drops on short trips

[DCMME]

Hey all- long time, first time. I appreciate any advice or assistance.

My 2021 MME has 32000 miles on it and I've had it for coming up on 4 years. I'm familiar with all the quirks of the car, including those that come from living in a cold weather environment. Lately though, on 3 separate occasions, it has behaved strangely- reporting a decline in battery percentage of 10% or so over the course of very short- about 5 mile- drives.

The percentage will go down very very quickly at first- by 3-4% almost immediately, and then continue to decline far more rapidly than normal. For instance, a recently trip took me about 2% to get there and then about 12% to get home, on the same route. In between these instances, it has behaved normally, including during 200+ mile road trip Any idea what's going on? It's the start of winter and has been relatively cold, but I've never seen this behavior before and it's not clear to me if it's actually the battery charge declining that fast (and what would account for that, as it shouldn't take that much power to heat the vehicle) or if it's something with how the info is being reported on the dash.

Thanks!

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[E90alex]

The BMS may be out of calibration. What are your usual usage and charging habits?

Eg how much battery do you typically use in a day, how often do you charge, what is your charging setup (voltage/amperage), what SOC do you usually plug in at, what is your charge limit set to, do you charge immediately or do you have a schedule, etc?

@Mach-Lee has a thread with how you can help the BMS recalibrate itself which may help your problem.

Also it’s pretty normal for short trips to eat up more range than you expect since the car needs to bring the cabin and battery up to temp again after each stop. Even more so if you normally park in a garage and preconditioned before you left and you parked in the elements before driving home.

 

[Mach-Lee]

FYI setting a battery-only departure time every morning might help with that.

Also try to use Level 2 instead of Level 1 and plug in each night so the battery can stay warm. This will minimize the initial % drop.

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