Two 4S LiPo batteries connected in parallel provide power to the Blue Robotics T200 thrusters as well as all the electronics in the enclosure. A parallel battery connection also allows the batteries to be hot-swapped. We obviously need to keep the batteries safe and dry, so enter the trusty Pelican Case. In this case, we use a Peli 1200. The Peli 1200 can easily hold two 4S LiPos between 5000 mAh and 10000 mAh. A Blue Robotics High Power Cable (12 AWG) connects the batteries to the electronics enclosure via IP68 cable glands. Velcro and a Nylon strap ensure that the battery box stays put on the HDPE deck. Stainless steel clamps connect the HDPE deck to the front of the stainless steel frame.
Interior Design
Instead of foam, we designed a 3D-printed frame to accommodate the batteries and a pair of Mikocopter LiPo decouplers inside the battery box.
Adhesive Velcro strips on the top of the 3D-printed frame prevent the batteries from moving around inside the case. Two Nylon straps provide added security.
LiPo Decouplers
While not strictly necessary, the LiPo decouplers add another layer of security. When connected in parallel a short-circuit or cell failure in one battery can result in a high reverse current to the second battery. The LiPo decouplers prevent a problem in one battery from damaging the second battery. These LiPo decouplers from the Mikrocopter shop work quite well. XT-60 connectors are used on both the batteries and the decouplers.
Additional Considerations
A maximum throttle (MOT_THR_MAX) of 40% helps to prevent a large voltage drop at full throttle. The LiPo decouplers also produce a small voltage drop. As a result, the voltage reported by QGroundControl or Mission Planner will be slightly lower than the voltage reported by a voltmeter.