Getting an EV to charge at its maximum advertised rate can be tricky and you often don’t know what the culprit for the lower speed is. It could be the vehicle, whose batteries are not at the right temperature, or the battery’s state of charge (usually if it’s too high) simply doesn’t allow for a ramp-up that reaches the peak charging speed during a session.
TFLEV tried charging the GMC Hummer EV from a 350 kW charger starting at just over 50 percent state of charge. The Electrify America charging station was chosen through the vehicle’s on-board navigation system, so it preconditioned the battery for maximum charging speed on the way there, but it didn’t actually hit the maximum, at least not on video.
GMC says that while the Hummer EV works in 400V mode during normal driving and operation, when it detects that it has been hooked up to a charger capable of delivering very high charging speeds, it is capable of switching to 800V, thus allowing speeds up to the claimed maximum, as long as the charger can provide it.
In this video, they don’t show the peak speed immediately after the vehicle was connected, but they do show the speed as it seems to stabilize around the 180 kW mark (and it will taper off as the state of charge increases). By the time the state of charge reached 65 percent, the charging speed had gone down to 170 kW.
After around 13 minutes, the vehicle had gained an additional 78 miles of range. It’s still a bit off what GMC claims, but had the vehicle been at a lower state of charge when the charging session was initiated, it could have been quicker. No charging curve or detailed information is provided in this video - it is just a basic look at charging the Hummer EV from a 350 kW charger, a test that can give you some indication of real world charging speeds.
Source: TFLEV / YouTube