That was also my experience with charging my SS9. I saw 9 kW on hot days pretty regularly, and as low as 6 kW on rare occasions. But to me that just means they need better cooling for the pack. I don’t consider it an inherent flaw of DCFC over AC charging. I also never got anywhere near the rated amount on my ‘17 SR with 2.5 kW charge tank, 1.3 kW OBC, and 3.3 kW ElCon charger on hot days. Often the combined charging rate was around 4.4 kW. Not sure whether that was because the pack was getting too hot or the chargers themselves. I couldn’t touch the ElCon with my bare hands for a good 10 minutes after charging, so I suspect the latter.
20+ kW charging should really be considered a minimum goal, and the high-end electric OEMs should be striving for something more like 50 peak, 30+ kW average over the session. That would bring 20->80% charge sessions down to 20 mins or so, and would convince a lot more people to try electric motorcycles. Now granted, 50 kW peak might only be achievable with liquid cooling of the pack, but I think sustained 20 kW can be achieved by just making pack cooling a higher priority in the design. More airflow and heat transfer to parts like the AC charger that can dissipate it more easily and don’t get used during riding.
At least when temperatures are moderate, look at the wattage on the charge station, NOT on the bike. The voltage drops on the bike (load) side, reducing the wattage at the same current (the current is the same on each end of the cable, unlike the voltage). IOW, the AC voltage to the bike's charger (or the battery in the case of a DCFC) will be a hair less than the wattage supplied. Consider it normal with your 3.3 KW plus 1.3KW=4.4KW instead of 4.6KW.
To get the full wattage the charge station would have to raise its voltage a little so you can get the full charge voltage on the bike's charger (AC) input or at the battery (DCFC). Or have a MUCH thicker cable with less loss (which will increase both the current as well as the voltage at the load end).
IOW, you're just seeing the normal voltage drop of the charging cable.
The difference is negligible anyway. Seconds of difference in charge times.
But like you say, what would make a big difference is battery cooling. While they figured out how to do this in cars, motorcycles probably don't have the room--but Energica has cooling for the inverter, just not the battery. And the battery would be more difficult to cool because even 90° F (32.2C) is hot for an EV battery. Normal EV battery temps are from 26 to 35°C (68 to 86°F). The center of that range to try for will be 77¯F (30.5 °C).
Better yet will be if somebody invents a battery with as many KWHs for its size and weight that has a much wider temperature spec. and doesn't require heating and cooling. But since EV cars can deal with this in other ways, I doubt if there is much hurry to take care of such issues on electric motorcycles.
-Don- Reno, NV
