When the 90F (32C) weather arrived in June, the 2017 Prime had three, full charge sessions in the heat of the day where the kWh decreased from ~6.1 to 5.9 kWh. With an air cooled battery pack, this alarmed me because the air cooled, early Leaf had problems of high temperature degradation. So I parked the Prime in the shade with 4% SOC and switched to the liquid cooled, BMW i3-REx. I learned with the earlier Prius, 2003 and 2010, that not driving 4-6 weeks can lead to a dead 12V battery. I also worry about lubricants thinning on the moving parts. So I swapped the Prime with the BMW two days ago and drove around after midnight, ~73F (22C) long enough to get the engine warmed up and lubricated. But I held off charging until ~4 AM to maximize cooling and got a 6.1 kWh charge. The Prime has an exceptionally efficient hybrid mode, +60 MPG around town. By going home as soon as the traction battery is discharged, I can use time-of-day scheduling to charge the battery between 4 - 9 AM. This maximizes battery cooling during the hot weather. I'll burn a little gas but I had bought in January. So I'll also burn up the 'stale' gas. I want to run the experiment of at least a week. This will determine if the traction battery kWh is stable. It also means time-of-day charging tweaked for temperature is a practical way to keep the battery in good condition. Bob Wilson
Time to update a table: Code: Date | kWh | hh:mm:ss 10/11/2018 | 5.636 | 1:44:42 10/12/2018 | 5.812 | 1:49:17 10/13/2018 | 5.667 | 1:45:40 10/15/2018 | 5.658 | 1:45:26 10/17/2018 | 5.779 | 1:49:10 10/18/2018 | 5.592 | 1:44:44 It looks like if I have any ICE operation and switch back to EV, there is a net increase in the added charge. Not huge, ~200 W or a mile, but visible in the data. If I time it right to EV the whole time and arrive at "--", I get a smaller net charge. Bob Wilson
EV only - lower left group EV+ICE - upper right, ~155 Wh, so you pay for some gas and extra electricity Bob Wilson
