davewill wrote:Isn't controlling the voltage the same as controlling the current? If the DCQC outputs a voltage above the battery pack's, a charging current flows. To control the charge rate, the BMS would request a particular voltage. With the add-on pack there, the DCQC has to supply more current maintain the voltage. The part I'm curious about is what happens if the BMS requests a voltage that exceeds the DCQCs current capacity because it doesn't know about the second pack. Hopefully, the DCQC would just modulate the voltage to output it's maximum current. However, it could decide it was an error for the BMS to request a voltage that exceeds the charger's capacity.
The question is where the current and voltage are being measured and where they are being regulated.
Current coming into the main bus splits into everything connected to the main bus. This not only includes the traction battery, but also accessories if the car is turned on. For an example, I've ran the A/C while charging from CHAdeMO once. The same must be true for any auxiliary range extending battery.
From what i understand the Leaf asks for current. I would guess it ramps up current until it reaches a voltage threshold, at which point it maintains that current until the voltage changes. At the same time the CHAdeMO station is communicating back to the car the amount of current it is sending. Basically the car asks and the station gives that much or less. If the car asks for 30 amps but the station can only put out 20 for whatever reason the station replies back "I'm sending you 20" and sends just that.