when to charge...

The only thing I can think of is the system waiting to let the pack shed heat.

 

Hummm
The traction pack heaters wouldn't switch on at all unless the driver turns on the option on the maintence section of the MID.

 

I went through my chargepoint history and found this. There were some others where it appeared to do more charging, so I'm not sure if it's always consistent.

 

That is just routine battery conditioning.

I see it every time I recharge on both ChargePoint at work and my JuiceBox at home.

 

Is off the default setting, the manual isn't clear on that? I would assume it is on by how it is presented.

With it off, the Prime should behave like the PiP when the pack gets too cold. Really low charge rate until the pack gets above freezing, or no charging at all.

I think you need to know the pack temperature to fully understand what is going on with the battery cooler.

 

I had to switch the heater on, but we got our Prime in August, so I'd expect that the dealer wouldn't turn the heater on during Pre Delivery Inspection and Setup.
And in parts of Southern California, Florida, Arizona, New Mexico, most Primes would never want the heater on anyway.
Yeah, I'm not sure which is default setting either.

 

Unless something was broken, the heater only comes on when the pack is below a certain temperature. Having it on in the smile states won't make a difference as the heater never actually heats. And why risk battery damage during a freak freeze spell?

The heater does have a precondition function where it keeps the pack warm for days at a time. If the car isn't going to be used during that time, having the ability to turn it off to save energy makes sense.

 

You could also set the timer with pre-conditioning as well. Just make sure the A/C is set for whatever you feel the temp should be and lock your doors after you leave. It’s what I do in the middle of summer and during late fall through early spring. It might be 90 in my garage but when I get in my car its about 72 when I leave. Likewise when I leave in the winter, the garage might be in the 30s or 40s, but the car is toasty warm.


iPad ? Pro

 

Pre conditioning doesn't do much to change the battery temperature.

In fact, last time I tried preconditioning for a departure time, it barely worked. I heard the AC running and waited for it to finish, but by the time I got in the car it was almost as warm as if it had been sitting in the sun (which it was).

And to defrost the windshield in the winter I often have to run it 2-3 times from the key fob, but maybe that's just a limitation of the heat pump.

 

Preconditioning uses the last setting from the HVAC system. The A/C battery cooling uses exactly the same system. If preconditioning is used to cool the battery, especially in OPs climate, I would set it to max cool just before I shut down the car.

Likewise if you use the key fob it uses the last setting so again to defrost set the HVAC to max heat just before you shut down the car.

Unsupervised!

 

The traction battery cooler runs the AC at max cool and runs the battery fans at full speed (faster than they normally are even during charging) for 30 minutes. Pre-conditioning runs for about 10 minutes and doesn't seem to change the battery fan speed. It might help a little, but it isn't going to significantly lower the battery temperature.

 

During a normal charging cycle, the charger (in the car) has to occasionally stop the charging and measure the state of charge of the battery, to know how to continue the charging cycle. This is something it cannot do while the battery is charging, and is standard behavior for charging lithium-ion batteries. This behavior has nothing to do with temperature, hot or cold.

 

Maybe, but if you're referring to the chargepoint screenshot I posted it's super low resolution, 5 or 10 minutes between samples. It stops charging for more than 10 minutes while the traction battery cooler is running. Otherwise during normal charging, chargepoint shows constant power. Maybe a higher resolution measurement would show what you're talking about. It probably only stops for a few seconds.