True, but MoonYeol was asking about changing internal power source (battery) from 3.7v to 5v as far as I know. While powering through USB port the voltage is being dropped by drop down circuit.
I think 5v li-ion batterries don't exist anyway, they come in multiplication of 3.7v (3.7, 7.4, 11.1v etc)
You're right, there is no such thing as a 5v Li-ion battery, the Li-ion chemical reaction that takes place dictates that so the 5v Powerbanks on Ebay must have a voltage booster (.. or drop) circuit in them.
I wonder if the USB's 5V is dropped down though, it's strange that the bass is improved and tightened while charging if it is.
Edit- Yep, from research it seems that the BH must have a voltage drop circuit because max input voltage for charging a single cell Li-ion battery must not excede 4.2V, (+- 0.055V) so this additional 0.5v must be where the better/tighter bass comes from?
Edited by Ari33 - 8/16/13 at 10:20am