Nowadays, with Lipos going to 30C discharge rates, practically all lipos have at least a 10C rating.1C is the capacity of the cell i.e if its 1500mah then the discharge rate at 10C is 15amps.Your CDI will draw much less than 2amps at full power so theres no need to purchase an expensive lipo with a higher rating than 10C. I would go for a 1500~2100mah cell rated at 10C which you can mail order for less than $20/-.