A new battery pack especially built for the DCS kit. In good sunlight it allows you to teach all day every day. Connect it to the Sunpower foldable solar charger with it’s 15m extended cable and you can teach whilst it recharges. Or use the smaller DCS 50 battery, which will give you up to 7 hours of usage. They are small enough to fit in the DCS backpack to make your kit very portable with no great set up. Just plug in and play.