The battery in the pictures is a standard size Team Orion Rocket 7.2v Nimh Pack. It's not a lipo.Coelacanth wrote: I wonder what they're using for a battery? Finding a LiPo pack that fits in the original Optima's battery receptacle is now damn-near impossible. Years ago, I managed to find some Gens Ace 2S packs that were very close to the original 8.4V NiCad pack dimensions, but even those required some minor filing down of the plastic battery holders in order to fit. Modern 2S LiPos--shorty or otherwise--don't even come close to fitting without major modifications. Furthermore, 8.4V NiCads were too long to fit inside the Optima body...the Turbo Optima had a wider body to accept the longer packs.
The nimh pack in the photo is 138.5mm long, any square lipo pack can be no longer than 139mm to be homologated for racing, and all will be the same size as the nimh pack in the photos.
The modern battery holders have been redesigned specifically to use lipos, Kyosho states that the chassis is designed for lipo. If you want to fit lipos in the original shaped battery mounts all major battery manufacturers make rounded packs that will fit straight in, for example from Hobbyking, Reedy, Team Orion. Schumacher even sell a Core-RC stick pack which is 5mm shorter, so it will fit into vintage car battery compartments while modern nimhs are too big. We have the situation where a modern nimh pack is too long to fit an old RC10 battery tray, while the Core-RC lipo will drop straight in.