Most people that I know dont worry about anything but the amps going to the Li-Po battery.

An AC to DC power supply will put out 13V in most cases, But so does my fully charged Car battery - And my fully charged Flying Battery setup. My Astro 109 tells me this, but seems to take it into consideration and charge the Li-Po at the rate I choose. Amazing these computers, smarter than we are.

I personally ignore the voltage drop and current draw from the charger, output from my Charging battery etc. What counts is do not exceed 1C going into the packs. I leave all that scientific and Technical stuff to the Brains that designed it.

I guess I'm just making it too simple, but it works for me. I just want my packs to charge, not explode, and work after the charge. Anything else I dont care about.