So, my electric lawnmower has DRM. Curing it is sadly not a simple matter like buying a flea collar or a course of worming pills.

Keeping the mower's existing sockets for feed in, and built two chargers (one takes grid 240 V AC, one takes raw ~24 V solar DC input).

I've been experimenting with building new battery packs, because most of the bad mojo is in the batteries (a full system-on-a-chip in each battery, to prevent owners from using off-brand anything).

I spot-welded together 10 (5S by 2P) second-hand lithium cells with an off-the-shelf BMS and the old battery's tabs to feed the mower. The first iteration wasn't very successful - it worked, but overheated after maybe five to ten minutes every time, needing a rest before using again. Used it through winter just fine, but spring grass was a nuisance.

Tried out the Mk2 today. Better (but still secondhand) lithium cells, and pure nickel strip. It overheated after 20 minutes. Found it was just one pair of cells, so I swapped them out and started again. No problems after that.

Wish I could mount a little fan in there, but there's no space. I can't even fit the usual plastic spacers on my cells.

But it is proven possible to liberate a electric lawnmower from DRM! And for a lot less (~$30 ea) than the cost of OEM batteries (~$120 ea).

#offgrid #diy #garden #electronics #drm