just connect 3 in series to get 10.8V 2500mah battery pack... or get creative and connect six in a 3S 3P to get 10.8V 5000mah pack ... 10.8V is close to the stock 9.6V pack the 3pk comes with so it will be able to handle it without any problems.

imagine a 5000mah tx pack... you'll only need to charge once a year!!