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How far does charge drop while plugged in before kicking back on?

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Hello and happy new year! Well, I pulled the trigger after much lurking and research (and general foot-dragging) and bought a 2015 P85D from a local forum member! I'll upload pics and details to another thread, but I have a general question which is pretty much summed up in the title:

That is, if I charge to x% and leave it plugged in overnight, I wake up and it has dropped maybe 2-4%. The app still shows the cable plugged in. I assume there is some sort of built-in hysteresis such that it is going to drop to a specific threshold before kicking back on and topping it up. Do we know what that threshold is? If I charge to 80%, I'd like it to stay there, not drop down to 78% (on principle).

I found this thread - Why does the battery discharge while plugged in? but it was really answering a different question. It was also from 2019, so its possible things have changed with software.

FWIW I have it set for Energy Saving = on, but still allowing the remote connection. I am not using any sort of climate conditioning, and the key fob is on the other side of the house. I expect temperature is a factor since it got down to the teens overnight (but 40s in the garage).

Thanks in advance!
adam
 
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Hello and happy new year! Well, I pulled the trigger after much lurking and research (and general foot-dragging) and bought a 2015 P85D from a local forum member! I'll upload pics and details to another thread, but I have a general question which is pretty much summed up in the title:

That is, if I charge to x% and leave it plugged in overnight, I wake up and it has dropped maybe 2-4%. The app still shows the cable plugged in. I assume there is some sort of built-in hysteresis such that it is going to drop to a specific threshold before kicking back on and topping it up. Do we know what that threshold is? If I charge to 80%, I'd like it to stay there, not drop down to 78% (on principle).

I found this thread - Why does the battery discharge while plugged in? but it was really answering a different question. It was also from 2019, so its possible things have changed with software.

FWIW I have it set for Energy Saving = on, but still allowing the remote connection. I am not using any sort of climate conditioning, and the key fob is on the other side of the house. I expect temperature is a factor since it got down to the teens overnight (but 40s in the garage).

Thanks in advance!
adam
My M3 LR has been plugged in since yesterday. In the teens outside. 50’s in the garage. Battery is staying steady at 80%. See screenshot from TeslaFi. Hope someone else has more info.
 

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...I wake up and it has dropped maybe 2-4%...
That is about right. I assume Older cars wait a few percentages drop before it's automatically charged back up again.

Newer cars only wait for a fraction of the percentage drop and it would automatically change back up again. Thus, if you plugged in and it completed at 90%, you won't see that number changes at all.
 
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My experience on my mid-2016 MS90D is that the behavior also depends on how you have set other input values, specifically whether you have scheduled charging enabled or if you have both scheduled charging/scheduled preconditioning disabled.

For the sake of illustration, let's say you have scheduled charging enabled, set to start charging every day at 6 am, and to charge to 70%. What I've seen is that it will allow the state of charge to drop below the set point during the day and wait to start charging. In my example this would be letting it drop possibly to 67-68% overnight, and then would kick in to charge starting at 6 am to bring it back up to 70%.

However, if you have scheduled charging shut off, then the behavior is different. In this case, whenever the state of charge drops below the setpoint it will start charging. This will result in potentially the car kicking in to charge for just a few minutes every few hours.

Now I have not ever played with preconditioning, so do not know how that influences this situation, but that's my experience.

The only other wrinkle I've noticed with scheduled charging is there is an allowance of about 5-6 hours after the scheduled charging time. The scenario here is say you have it set to charge starting at 6 am, it charges, and then stops. Say at 8 am you leave, do a few errands, and return home a couple hours later with your car may 10% below your charging set point. What I've seen in this case is I plug in and the car will automatically start charging. However, if I were leave for the day, not return until that evening, say 6 pm, then the car will not start charging when I plug in but wait until the next morning and my scheduled charging time. It's been a while since I've encountered this to recall if the window is 5 hours or 6 hours, but by memory it was in that range.

Final caveat ... I've not been using either scheduled or preconditioning for the past year, have both turned off and manually managing when I want to charge, so it's possible some of these behaviors may have changed. That's especially possible with the new V11 update where all sorts of things appear to have been messed up, so honestly nothing would surprise me at the moment in terms of my car suddenly starting to want to charge when I'm not expecting it.
 
Do we know what that threshold is? If I charge to 80%, I'd like it to stay there, not drop down to 78% (on principle).
There is potentially another factor at play here: You may charge when the battery was warmer because of recent driving or the ambient temperature was warmer than when you checked the value in the AM (battery cooled off). The charge is still mostly the same (volts wise), but the % will change based on the temperature of the battery. Note it's also possible (probable) that you can charge to 80% and the next day see a value of 82%. That is because the battery warmed up after a charge.
 
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When I have left my 2015 S85D plugged in for weeks long vacations, I've noticed that the charger tends to kick in when it has lost about 10 miles of range (which would correspond to about 3 kWh). This happens every 3-4 days. I usually leave the car charged to about 60-80%.
 
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A bit off topic, but my experiences mirror PCMc. I use scheduled charging to start during the coldest time of the mornings in winter to help keep the battery as warm as possible when the temperature drops. It only takes 2 to 3 hours to recharge for my normal driving. I think warming the battery during the recharge may increase the battery life.