I got tired of struggling to keep the phone and DJI Osmo Mobile charged while filming. This 18V drill battery mod powers the Osmo and the phone off a battery that will last all day.
1 - Buy the DJI Osmo external battery adapter.
2 - Cut the top off a ryobi 18V flashlight, and use the lower part of the handle that attached to the battery
3 - 3D printed an adapter out of polyurethane rubber @ninjaflex
4 - solder the DJI Osmo battery adapter wires to the 18V battery connector
5 - connect a 5V USB outlet to charge the phone
6 - glue the 3D printed adapter to the 18V flashlight base
7 - slide the handle of the Osmo or Osmo Mobile into the 3D printed adapter and tighten the screws
8 - insert battery and start filming!