Charging while hot?

Charging while hot?

Just purchased a 2014 (june) Model S 85. We live off grid, and want to charge while the sun shines. Installed a TESLA wall charger, and we have limited the car to 24A.

It was charging at the full 24Amps, (17 miles/hour), but it has dropped down to around 8 miles and 16 Amps. The panels are producing 11 KW, and our set of house batteries is at 90%, so there is plenty of power available.

Is it normal to have it drop down when it gets hot? Currently parked outside while we get garage organized. Car says interior temp is 103F.

tes-s | 06. kesäkuu 2019

Not until the battery is almost fully charged. It could be some power is used for cooling, so it is still drawing 24amps but the charging has slowed. I think it would still show 24A being drawn though.

Did you try bumping up the charging limit?

azmikejan | 06. kesäkuu 2019

We can't really boost the charging limit because our inverter is only 8kw. We limit the charger to 30Amp and the car to 24. We need to keep the house running!

murphyS90D | 06. kesäkuu 2019

What voltage is the car reporting. The car monitors the voltage as it ramps up the current. If it sees too much of a voltage drop it will reduce the current on the assumption that the circuit has too much voltage drop and could be a fire hazard in the house wiring. | 06. kesäkuu 2019

@azmikejan - This is normal when the car starts to get above 90% SOC or so. See these tapered charging charts I made: While shown for Superchargers, they apply to AC charging too - just limited to what maximum you are charging at.

tes-s | 06. kesäkuu 2019

+1 @murphys90D. Could be that your inverter is simply maxed out, and at some point did not maintain steady voltage. When the car sensed this, it dropped the current. If you stop and restart charging, it should go back to 24A assuming the inverter can handle it.

Do you monitor your inverter output - did it hit 8kW? Is it rated for 8kW continuous? Charging at 24A is 70% load by itself.

azmikejan | 06. kesäkuu 2019

We do monitor the inverter. When we bought the property, we replaced the 13 year old system and panel and swapped the lead acid batteries for lithium (couldn't wait for TESLA powerwalls). We never hit 8kW, not even 7. It is rated for 8kW continuous, and bursts to higher. We don't know how clean things are, powerwise. The wine fridge and TV don't care that much;-)

adspguy | 06. kesäkuu 2019

When the car limits charging due to a voltage drop, it reports this on the display. Did you get a message? The message does go away when you unplug though.