Limiting Maximum Battery Power Draw

Sometimes power needs to be limited to prevent issues with battery sag or overheating. This can occur because of the use of lower C rated batteries, high power motors, high ambient temperatures, uncooled engines or ESCs, or other reasons. This topic discusses ways to limit the maximum power draw from batteries.

Methods to Limit Maximum Power Draw

The first and simplest is to restrict MOT_THR_MAX to a lower value. This limits the maximum throttle controlled allowed. Unfortunately, this will not set an exact power limit and might require some trial and error to find the right setting.

A better way is to use a power limiting parameter (shown for first battery monitor):

• BATT_WATT_MAX

The BATT_WATT_MAX parameter can be used to limit the total wattage that can be drawn from the battery(s). If battery power exceeds this value then the system will reduce max throttle (MOT_THR_MAX) to lower the power draw. If power demand is reduced, the max throttle will slowly grow back to MOT_THR_MAX. Use 0 (default) to disable this feature.

The MOT_BAT_WATT_TC parameter can be used to adjust the rate at which the max throttle is reduced when the battery power exceeds the BATT_WATT_MAX limit. This can help to fine-tune the response to high power situations and prevent sudden drops in throttle. Smaller values will result in a faster response, while larger values will provide a more gradual adjustment. The default value is 5.