External Power - White Lightning M-Series

Guest Discussion
1

Hi, we bought a White Lightning M2827 (28 volt / 27 amps) external power supply for our SR22 G3, the goal being to run the avionics on the ground without depleting the battery.

We followed the POH instructions (connect external power, BAT1 on, AVIONICS on) but I notice with this configuration that BAT1 still shows a discharge (-7A) whether external power is connected or not. I wouldn’t think the battery should be showing a discharge with external power applied, are we missing some step?

Side note - the only difference we see having the external power supplied is with the Bus Volts. With external power, Ess, M1 and M2 all show nominal voltage (27.5, 28.2, 27.5 respectively). Without external power, Ess, M1 and M2 show 23.9, 24.6, and 23.9 volts.

2

This indication is to be expected. When you are operating on a GPU, the current flow is negative from the perspective of the current sensors, so it shows a negative value.

You can use the voltage as your guide. As long as you have more than 24 volts and the engine is not running, you are operating properly on the GPU.

3 Likes
3

Bill has it right. You should see 26+ Volts on the battery indicator if the external unit is working properly. If not you will barely see 24V. Do not rely on the BATT 1 discharge notice. It si doing that because it is fooled by the alternator nor being on.

4

Thanks guys