gas gauge for 2 li - ion batteries

hi 

I need some help in selecting the right gas gauge for my application.

I am using 2 li - ion batteries connected in series (i need 7V) but charged separately (because I want to be able to cahrge it from usb).

so the battery are connected in series and I uses switches in order to disconnect it fro each other and charge from bq 24163 charger.

now I want to add gas gauge.

the problem is that as I understand the gas gauge measure the the dQ (charge passed through it). 

but when I charge the batteries and discharge them their configuration is different in addition I dont know if I can put a 1 cell gas gauge on each battery when they are connected in series (because it will feel 3.7- 7.4V and cant be connected to gnd) so how can I solve this issue?

thanks in advanced.