Unusual loss of charge

[doghousePVD]

I arrived at my in-laws with 10%. Unfortunately I could not start charging for about an hour. My SOC dropped to 4% in that hour! Sentry and HVAC off, ambient temperature about 55°F.

Last hour of driving below 50 mph on non-Interstates with no hard accelerations. Battery should not have been stressed or overheated.

I have no idea I could lose 6% in an hour. Any ideas?

It’s now charging at 23 A on a 10-30. 16 hours of charging to get back to 90%.

2018 MX 100D with 100,000 miles. I’m the only owner.

 

[LoudMusic]

Someone else probably has a better answer, but maybe just the bms getting a better reading once there was no load on the battery. When was the last time you charged to 100%?

 

[doghousePVD]

A week ago

 

[ucmndd]

This is normal when parking your car under ~20% SoC without charging.

My 2016 S did it every single time, “losing” 4-6% within an hour or two of parking at low charge. Many other reports of the same. You don’t actually lose that much energy… just the BMS doing BMS things.

Doesn’t seem to be anything to worry about.

 

[Rocky_H]

Yeah, normal and is usually a combination of two or more factors:
Load off the battery, so it can recalculate unloaded. Also temperature almost certainly cooling down. That doesn't meant it was "overheated", as you said--just nice and cozy warm from being in use, and then cooled down from being parked, so lower temperature equals lower energy.

And if you look at the voltage curve of lithium ion batteries through their entire state of charge, they are pretty flat through the middle, but they curve sharply up at the top end and sharply down at the bottom end. So when you're down in that 5% to 10% kind of area you're talking about, the little bit of battery cooling and reduced energy is probably going to be dropping off the voltage more steeply, and will show up as a more significant battery loss than if this were happening around 40% or somewhere in the middle.

 

[doghousePVD]

OK , thanks all. I had never noticed since I usually charge immediately when I arrive so low.