Flight lasted about 4.5 minutes
Battery went from 97% to 5% in that time
Never went far - maybe 100 yards from home
At about 216' AGL, battery was at 50%
At 275' AGL, battery was at 25% - Low Battery Warning
Went into RTL and Solo started climbing
At 316' AGL mode was switched to Fly and battery was at 17%
By the time Solo hit the ground under power the battery was at only 5%
Why did the battery only last 4.5 minutes? I'm not sure if the Tlog can show that. This was the primary failure, but it was not catastrophic.
Hind sight is 20/20, and I don't mean to hit you while you are down, but this is a learning opportunity for us all:
Why was RTL Altitude set to something higher than necessary - in this case over 316'? RTL Altitude should always be set to the minimum height necessary to clear nearby obstacles. In this case valuable power was wasted during the climb from 275' to 316' when you realized what was going on and switched back to Fly. Battery drained from 25% to 17% in this unnecessary climb.
Why continue the flight when power was dropping so fast? The battery was already down to 50% by the time Solo reached 216' at 3.5 minutes into the flight - this was not the time to start climbing higher. Under normal circumstances, the next 25% of the battery power might get used in a similar time as the first 50% got used.
Something went wrong to cause the power to drain so fast, but the crash looks like it might have occurred while in Fly mode and scrambling to get the Solo home and on the ground before power was out completely.