We used a single 6S (22.2V nominal) 8Ah pack in Coyote which was running two 24V, 800W scooter motors, and two electric actuators (I'd add a third actuator and a brushless motor in here too but the chainsaw saw such little use that it's negligible ) and usually only took about 3Ah out of a pack for a full three minute battle. The battery pack itself didn't have a footprint much bigger than a standard TV remote, and a little bit more in height.

Obviously depends what you're running (Constrictor, right?) but you'll be able to go a lot smaller physically and a bit smaller in terms of Ah and still be more than fine. And prepare to save a ton of weight. We got our pack from Optipower (30% discount for FRA members) but plenty of people have had success with Hobbyking packs, as per both of Chris's links.

In terms of chargers, I just use the same little chargers that I use for my featherweights but they're a bit weedy for a fast turnaround. Gary (PP3D) and several others use a quad charger (Reaktor I think it was called) from Hobbyking that is beefier with the right power supply behind it and can obviously do up to four packs at once. Not too sure on budgets as I haven't looked at them for a while, but there should be a few options on HK.