Comment by ACCount36
2 days ago
> Unless you specifically design for it (specifically, with a dummy load), the efficiency of the system is inversely proportional to its ability to do this. You need a secondary system.
Many multicell BMS already have this kind of "power shedding" capability. They use it for cell balancing - to equalize voltage between cells with slightly different characteristics. This is desirable despite the power waste, because it reduces wear, increases charging efficiency and allows battery packs to last longer.
Some battery packs are also designed to be able to dump enough power into heat to be able to keep the batteries warm during extreme cold.
The amount of power you can dump for balancing is just a fraction of the charge/discharge power (because it only needs to offset differences in self-discharge rate). So you still need a proper dummy load when you want to dump more.
Similarly, the heatsinking capacity of the battery is designed for charging/discharging losses (say 5% of charge/discharge power).