I have seen this battery gauge which is available for 1S or 2S but can anyone see a problem with extending the number of cells by feeding the 'CELL' terminal by a resistive divider from a battery made of more cells?
Clearly then a suitable Vdd supply will be needed for the chip.

http://www.farnell.com/datasheets/2579716.pdf

 

OK, no-one else knows either.
I've ordered one and I will try it - but don't hold your breath!