Battery technology question ... There *must* be someone out there who knows about this stuff and is geeky enough to work it out:

If I want to get max usage from a fully charged phone and external power bank combo should I:

1. Run down phone <20% then run/charge simultaneously from power bank.

2. Run phone down to say 70% then run on power bank back to 100%. Repeat.

3. Start with phone on power bank until that is dead then run down phone battery.