GetOffYourGas
Well-known member
mkjayakumar said:Tesla SuperChargers can charge at a Max rate of 90kW. It doesn't mean they have to or they do charge at that rate. The charge rate is negotiated between the car's BMS and the EVSE, and the actual charge rate will be a lower of the two numbers between these two devices. In fact as the SoC or the battery temp increases, the charge rate decreases progressively and substantially because the car's BMS negotiates a lower charge rate as the battery fills up. So what starts up at 90 kW rate when the battery is near zero will reduce to a trickle approaching 80% and above.
So one could connect a 40 kW battery to a 90kW supercharger and the car's BMS will negotiate a 30 kW charge rate, which will be less than 1C.
This might be a reason why Tesla decided not to have a supercharger access to 40kWh battery, because an hour of charge will give substantially less number of miles in a 40kWh than an 85 kWh, making supercharging much less useful in long distance driving for EVs with smaller packs. You might get 100 miles in a 40kWh Tesla on an hour of supercharging session, which is not enough to cover the distance to the next supercharger to continue your journey.
I agree completely. I think the average consumer isn't going to care about how many kW are being transferred into their car. They just care about adding enough juice to comfortably get to their next destination. So that means that either the 40kWh battery will have to be charged at a stressful 2.25C rate, or the owner is going to be frustrated that they can't get the same benefit out of the supercharger network as the 60kWh/85kWh owners can.