Homelite Lawn Mower Battery DIY Housing Upgrade

thingiverse

I bought a used Homelite 24v battery-powered lawn mower. It came with a heavy lead acid battery that was failing to hold a good charge. I acquired some very high quality lithium iron phosphate A123 brand automotive battery cells and used 16 of them to replace the two 12v lead acid batteries. The result is a battery that weighs a lot less, charges in two hours instead of 24, and lasts longer per charge. And when it is depleted, it just stops rather than getting weaker and weaker for the last 10 minutes. The "thing" I'm posting here is just the black part shown in the photos. This is a housing designed to drop into the Homelite plastic box once you remove the lead acid batteries. With this housing in place, you'll have two slots to insert two battery packs for the A123 cells and a BMS unit (battery management system) in the center with some airflow around it. The point is that everything will fit tightly into the original plastic box without requiring you to stuff styrofoam or anything flexible or flammable inside the pack. Wire it all up properly, screw the red top back on, and you have a durable, high quality DIY lithium rechargeable replacement battery that breathes (a LOT of) new life into your old battery powered mower. This project is much more an electrical project than a 3D printer project, but I want to share in case someone else can get some use from this. I spent a lot of time and effort designing this and I'd love to know that it helped someone else besides just me. Also, note that the green battery pack housings in my photos are a separate thing I designed, which you can find by searching Thingiverse for its thing number 4705802. The strengths of this housing in its final design are that it's very strong (I used PETG) and durable, uses relatively little filament with the large hollow in the bottom, provides several options for running wires and hiding connectors, and is easy to take apart in the event of a problem or cell failure in the future. I put little handles on the top to help me pull it out of the Homelite battery box, and what looks like a tiny handle in the middle so I can zip tie the BMS in place. (I didn't bother doing that, in the end.)