Help with multi charging.

I have a project that uses 2 LIPO 1000 maH batteries connected in series to give me 7.2 volts. I also have a charger that will charge 5 batteries at 3.7 volts

What would be the best way to charge the 2 batteries from this charger. As I see it maybe the best would be to isolate the 2 batteries with a switch and charge individually at 3.7 or could I connect 2 charger outputs to give me a charge of 7.4.

Thanks in advance