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Normal for battery to under-charge?

Aug 7, 2020
824
1,737
USA
Past few days I’ve noticed the car reporting 77% battery even though I’ve set the limit to 80%. I’ve read it’s normal for the battery to overcharge a few percent but what about undercharge? I haven’t changed any charging habits recently. Car charges in a garage starting a midnight and does sit a few hours before I leave in the morning. Live in So Cal so no freezing temps. No sentry mode or preconditioning.
 

Apprunner

Member
Jul 2, 2019
599
703
So-cal
Past few days I’ve noticed the car reporting 77% battery even though I’ve set the limit to 80%. I’ve read it’s normal for the battery to overcharge a few percent but what about undercharge? I haven’t changed any charging habits recently. Car charges in a garage starting a midnight and does sit a few hours before I leave in the morning. Live in So Cal so no freezing temps. No sentry mode or preconditioning.

If I set to 80%, it can be both higher and lower. Most of the time, its slightly higher, but being lower isn't uncommon.
 
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KenC

Active Member
Sep 4, 2018
3,943
3,642
Maine
How about Smart Summon? Okay, saw your sig file, funny way to describe it.

Anyhow, my car lives outside and it's set for 61% SOC, but when it charges, it must stop at 60.51%, because it almost immediately drops from 61% to 60%. And, it almost always is around 58 to 59% by the morning. Then again, I live in a cold state. Stats tells me I have phantom drain of 0.1mph in summer to 0.5mph in winter. It's easy to see losing 6 miles or 2% overnight, so 60% becomes 58%. I don't have anything running at home, no sentry, not preconditioning, no smart summon, either.

From Stats, you can see quite a wide range of phantom drain rates.
IMG_9893.jpeg
 
At least on my car, you can't know what you set the limit at, since it doesn't say. If you want a bit more, just move the 'limit' line a little bit more to the right, and problem solved :).

When you set the charge limit in the app it actually does tell you the percentage along with the bar in the graph. Always wondered why the graphic in the car doesn't do the same. Or why even have the slider at all. It's more of a visual for after you set it. You just type in the value and then it shows you on the graphic.
 
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I have seen similar to the OP. However mine behaves more like Let's Drive comment above. I drove the car down to 48% like he said, but it never fixed the "issue." I still got 88%-89%, and have not seen 90% for more than a few minutes since early December 2020. Having said that, the garage has been between 37F-47F since then.

I posted about this topic in another thread, and the conclusion was that this behavior is normal.
 

elptxjc

Member
Dec 15, 2019
833
270
El Paso, TX
When you set the charge limit in the app it actually does tell you the percentage along with the bar in the graph.
Yeah, you're right. Didn't notice the super little white numbers at the bottom left of the battery graph :). Thank you. Set it to exactly 70%, to see how much it charges. Before it went to 71 or 72, but set the limit on the screen. I honestly don't mind if it's 1 or 2 percentage points more or less. But if charge level is not dead on, prefer it to be a bit more :).
 

Gasaraki

Active Member
Oct 21, 2019
2,325
1,611
Syracuse, NY
Past few days I’ve noticed the car reporting 77% battery even though I’ve set the limit to 80%. I’ve read it’s normal for the battery to overcharge a few percent but what about undercharge? I haven’t changed any charging habits recently. Car charges in a garage starting a midnight and does sit a few hours before I leave in the morning. Live in So Cal so no freezing temps. No sentry mode or preconditioning.

I've had mine "undercharge" but never 3% under.

Also on another topic, don't mess with the app charging bar when the battery is cold because that scale changes with the temperature of the battery.
 
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