For those who are in cold climates and without battery preconditioning, there is an interesting post on the Ioniq 5 reddit group by a user with an I5 without battery preconditioning that seemed to
mimic DCFC battery preconditioning. Here is a graph of his OBD2 data (note: I think the person mislabelled the Battery Min Temp with % instead of C):
With Winter Mode enabled (the user enabled it 1 min into charging) and at 9% initial SOC plugging into the DCFC triggered the battery heater, but it seems for whatever reason even though the Batt Min Temp reaches 20C the power does not increase. Almost as if the BMS checks the Batt Min Temp on initial plugin to determine if the batt heater is needed then ignores it and instead monitors the batt heater temp to know when to turn it off and Batt Max Temp to check for overheating of the battery. Interestingly unplugging and plugging in allows the power to increase to 200+kW and maintain above 133kW up to about 80%. Based on what we know about the Battery Min Temp and how the BMS seems to use it as an indicator when to increase power requests of the DCFC, the reddit user could probably have unplugged and replugged in at 17:13 (16min) into charging because the Batt Min Temp had reached 20C and still seen the same increased power effect. Had they unplugged/plugged in this manner, the charging time to go from 9-80% SOC would have roughly been 26 min. However the caveat to this method would be that the colder the exterior temp, the longer it will take to get to 20C and thus waste time heating the battery before the power increase.
Maybe not all that helpful, but interesting that the BMS does not request more power from the DCFC once the Batt Min Temp reaches 20C.