The Siku Kuhn fertilizer spreader was one of the first accessories I bought for my RC tractors and I had always planned to use it and the butterfly mower as battery packs.

My initial attempts at tractor conversions left no space for a battery in the models because I used through hole components an larger servos which took up way too much space. As a result I was expecting to need to provide power from a source external to the tractor and I taught a 9 volt battery would work perfectly. Since then I’ve miniaturised the design and have a bit more space to play with so I changed to 3.7 volt LiPo batteries instead.

The fertilizer spreader is an obvious choice for a battery pack because it is basically just a spacious box with a hinged lid, you really couldn’t get a more suitable attachment.