DrRadium I bought one and made by own spare battery using a 400mAh battery (2.5 capacity). Photos are with my review. Here is what I wrote (in case they won't post my review). I opened the battery, confirming it was a standard 7.4V 2S Lipo, It was nothing special, JJRC could have sold them for big profits. I reassembled the case and made a cast of it in silicone rubber, used urethane resin to cast copies, drilled holes for the wires from the battery and used tiny blocks of copper, balls of solder, or conductive epoxy connected to the wires for pads. Polarity is shown in pictures. Don't screw it up, it will probably fry everything. I used a ZOP Power 7.4V 400mAh 2S Lipo from Banggood to wire it up. 2.5x capacity and is the perfect weight for a counterbalance on the glasses.. It worked great as shown in the photos. You have to charge it with a balance charger, but you need one for drone batteries anyway. You could also open the body of the unit carefully and solder wires directly to the terminals that contact the battery and connect these wires to a polarized connector to attach to the battery instead of using my cast faux battery end.There is nothing special about the stock batteries, they could have sold them anytime at a very nice profit. They just choose not to. Fortunately it is easy to cut them out of the loop and make your own.