You might consider the fact that a Lithium Ion battery if discharged below 20-25 % generallly does not fully recover. This may be why your getting poor results.
If your normally running it down to the levels your indicate it may be wise to avoid it.
This is not a BB issue. All LI batterys have this issue.
Depth of discharge Discharge cycles
Cycle life as a function of depth of discharge
A partial discharge reduces stress and prolongs battery life. Elevated temperature and high currents also affect cycle life.
100% DoD 300 to 500 cycles
50% DoD 1200 to 1500 cycles
25% DoD 2000 to 2500 cycles
10% DoD 3750 to 4700 cycles
How to Prolong Lithium-based Batteries - Battery University