I have a CE OSD. I have tested Nova OSD..and here again the big subject add infinitum is the mAh reading. I'm planning to purchase a storm OSD.
Why doesn't someone do the test with a separate meter mAh.
Connect a Watt's-Up style meter on the lipo. Turn on everything and have it working FPV on the bench. Run the motor etc. Get some mAh. Then recharge the lipo.
Compare the Storm mAh to the Watts-Up meter.
My CE OSD mAh is very accurate. Better than 5%.
Something like this meter. There are other and cheaper mAh meter available.