android04
Active Member
This is the exact behavior I observed a year ago when I was playing around with Service Mode in my Model 3 (where you can see the current in each individual phase module as well as a lifetime kWh counter that shows how much each has been used).The power electronics in the on board charger that converts 240v (or 120v) AC to the nearly 400v DC needed to charge the battery. The reported behavior has been that charging at or below 16a uses one charging circuit, Charging between 16a and 32a splits the load across two of them and >32a (in cars that support it) splits the load across all three. If I had to guess at the reasons WHY it would be programmed that way, I would say that it comes down to efficiency. The power electronics are probably less efficient at low amperages, so it makes more sense to run one circuit at 16a than two at 8a or three at 5.33a.
I have a HPWC that can charge my LR RWD at up to 48A, and knowing that my car has 3 different phase modules for charging that can handle 16A each I was curious on how it divides the current between them. So I adjusted the charge current from 48A down to the minimum (I believe it was 8A) little by little to see the current between the 3 modules. 0-16A was on one phase. 17-32A was split evenly between two phase modules. 33-48A was split evenly between three phase modules. So if you want current to be evenly split between two or three modules to limit stress on them and equally wear them out, avoid 16A, 32A (and use 33A if your car and EVSE can handle it), and 48A (go a little lower if you want to avoid maxing out the phase modules, like 42A) settings. For example, looking at a picture I took of setting my charge current to 34A, each of the 3 phase modules showed a current of 11.4A at 235V in the Service Mode screen.