Fast charging guidelines (for Zoe)

When time is money (both re. your own time as well as how the operator calculates the rates), the following guidelines will help you, especially in winter. The’re all fairly obvious:

1. Try to avoid fast-charging starting at a high SOC to avoid entering the area where the car squeezes the charging power. This squeezing can start as low as 35% SOC when it is cold. Drive as far as possible to keep the charging power high for as long as possible.

2. Try to charge with the highest possible battery compartment temperatures. As driving increases the temperature substantially, try to fast-charge at the end of a drive, not i.e. the following morning. Fast charging itself also increases the temperature.

3. Quit fast charging as soon as you can. If there is a slow-charger at your destination, just fast charge until you can reach it.  This ensures fast-charging at the highest possible power and trades “real” waiting time (twisting thumbs) against “virtual” waiting time (car is charging for a longer time, but you’re not waiting for it doing nothing).

A rule of thumb is that squeezing from 43 kW starts at 30% SOC plus twice the battery compartment temperature for a Q210, and from 22 kW at 65% SOC plus the battery temperature for an R240. Note that this is for the 22 kWh battery. The 41 kWh battery behaves substantially different, but we don’t have enough data yet.

2 Comments on “Fast charging guidelines (for Zoe)

  1. Let me get this right. In a rapid charge on a summers day, say 20 degrees centigrade, the calculation would be 30 + 20 + 20 = 70%.

    • VERY roughly yes. The “start of throttle” SOC percentage is probably a bit higher. The heatmap will tell you. The charging graphs will tell you exactly of course. The formula is more for readers to get an idea.

      And we are talking the battery temp, not the ambient. Note that especially after a long and stiff drive, the difference can be very VERY substantial.

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