I have 3 lipos that I use in my RC18T all are 2s:
- Rhino 25C 1750 pack from Hobby City.
listed here This pack is a bit heavier than the others because of the extra heavy wire and the extra shielding in the packaging. But it also has the most punch and it's really cheap. They have a few different sizes of pack that would probably fit.
- Hyperion Lite Storm 1500 2s. This pack is the smallest/lightest and also the most expensive. It doesn't seem to have as much punch as the Rhino pack.
Found here
- Loong Max 1800mah battery from Hobby City. I don't think they make these anymore but I'm sure they have a Zippy pack that has the exact same specs somewhere on their site.