Curiousity: Voltage Drop

[MrForbes]

I don't know what the "science" of the phenomenon is, but a rather simple explanation is that electrical power is produced by a chemical reaction, and under high current load, the reaction cannot happen fast enough to keep the voltage up. Too many electrons leaking out, not enough being generated to replace them, so the voltage drops.

I hope a someone with more knowledge of batteries can explain it to us....