Battery drain when turned off

Well, I can tell you that in the summer, on a really hot day, out of curiosity, I looked at the app to check how hot the cabin was, and it said 49°C. I then glanced at the battery, and it had dropped 9% in 3 days. I was surprised, could it be damaged, or is it cooling the battery due to the hot weather? Took it indoors, and it was stopped for 1 week and the battery dropped 0% during that week. Does this mean the car uses some battery to maintain the batteries under certain parameters? Perhaps.

I suspect this might be the case, yes.

Oh wow, don't think our Atto has ever gotten that hot! But that makes total sense. We'll have to leave the car stored for a while, and it'd be quite an inconvience to arrive back and find the battery flat 😅 Luckily it's a warm parking hall at an airport, so based on this we should be ok.

How long have you owned your Atto? Severe main battery drain is common if the 12V battery has failed. It will need to keep charging the 12V and hence drain the main battery.

When I am using "Sentry mode" it takes 2% a day. When not than around 1% a week. But I have a Dolphin. Temp. is a little bit cold -15, -20 last week. This week wil be -35, -38C.

When leaving it parked for an extended period, it’s actually better to leave it to 60-80%, as 90%+ degrades the battery when not used (yes, even LFP battery.)

I can tell about BYD Seal U, probably it applies to Atto as well. I observed rather regular overnight 1-2% battery drains in sub-zero weather. I observed somewhat similar behavior in very hot weather, 35+ Celcius, but it wasn't as strong as cold weather. Mild warm weather, 20-23C, is the optimal for EVs, you can get close to WLTP range.

You also lose 1-2 percent of you leave schedule on all the time...which I do

Didn't think of that! I also tend to have it on all the time, I'll see if turning it off helps at all

The BMS keeps the battery on working temperature all the time. In these ultra low temps, the AC will be working full time to leave the battery in proper use temperature (above 0°). -20° would kill your LFP battery if you tried to charge it, for example.

J,avais exactement le même problème : perte de 3% par nuit dans mon garage. J’ai tout vérifié, surtout la batterie 12v qui était parfaite. Je l’ai porté au garage BYD ( Maroc) . Ils ont effectués une mise à jour du système et le problème a été résolu immédiatement. Actuellement perte 0% même en exterieur a 10 degrés Celsius

Had a similar problem with a dolphin. The cause was the air con turning it self on off throughout the day. BYD said there aware of the problem and current fix is to have the air con off before shutting down the car. Heard similar issue with sealion as well. Might not be the same issue but might help someone else.

Check that you don't have a pending OTA.