Mower Batteries

Was away for a while and have been busy with other things and haven’t had time to wrap up the electric mower project. Just went to give it a quick test drive, since I hadn’t tested the brake switch that shuts off the motor. Good news is that it works, the bad news is one of my two batteries is dead, or at least pining for the fjiords. Was able to drive around on 12V, but slowly.

The battery was old and was the original starter battery for the mower when it ran on gas. I bought a second just like it to get up to 24V, but it wasn’t really ideal for the job. I’m thinking of options, including some nice new lithium batteries. They are expensive (relatively) but my next project was to play around with some solar panels and battery storage, something that could be useful here in Texas. I have heard of talk of people using their electric car batteries as home storage, so why not use a riding mower? Ok, maybe just to power my shed.

One Last Piece

The electric riding mower is almost ready for its first test. I am happy with the drive train and have even added a switch to the brake that that turns off the motor when braking. I was going to turn off the motor manually when braking, but too easy to burn up another fuse that way, or worse.

Still playing around with how to attach the lift mechanism to the blades. My biggest concern right now is what happens when you bump into something. The old gas mower was heavy duty, and I still managed to bend and break stuff. This won’t be as strong and will break more easily. I just don’t have a good feel for how much movement to allow. The old deck was mounted at four points which was more stable. This will be just two points. Maybe I should have kept more of the old lift mechanism, but it was a bit complicated. Right now I’m thinking of ways to limit movement. Things will break if you hit them hard enough, but I’m going to try to keep it to a minimum. Actually I suppose I will be easier on this machine than I was on the old gas mower.

One other bit. Sometimes my progress depends on Amazon deliveries. There are two parts to the old lift mechanism. I want to reuse them and each has an advantage and disadvantage. I’m also learned that although they seem interchangeable, one is maybe a quarter of an inch offset. Nothing some big washers wouldn’t fix. Except I didn’t have any big washers. So two days to mull it over while Amazon ships my washers.

Electric Mower Blade Covers

I glued the PVC pipes for the blade unit and even painted it all black. I needed some way to cover the blades, mostly to prevent accidents. Not likely these little blades will be throwing rocks around. I found some plant saucers on Amazon that looked like they could do the job. The problem is how best to attach them. I bought some aluminum strips and decided to bolt them together. Some cutting, drilling and bolting and I made a nice little cover for the blades. Bought some u-bolts to attach the cover to the PVC pipe, which is going to require just a little more drilling.

I went back and re-installed the big handle to raise and lower the blades and re-purposed some of the mechanism used to lift the original deck. Instead of four offset lift points, I now have just two parallel to each other. The last job is to figure out how to connect the whole blade unit to these lift points. It needs to be offset to give some overlap in the blade paths so that there aren’t uncut stripes in the grass. Also hope the whole arrangement is flexible to handle a bit of collision but not so flexible that the blades move around in normal use. Almost there.

Electric Riding Mower Direct Drive Test Video

Forgot to mention I also have fully functioning brakes, an important bit. It is much faster than the chain drive but can still run it full bore at maybe 10 m.p.h. Enough for a mower, I suppose. Also this didn’t seem to put any strain on the motor, which stayed cool. Also noticed my older battery is going bad and neither is fully charged. So maybe it would be a little bit faster. I’m starting to lust after those pricey lithium batteries. Much quieter than the old mower but the transaxle probably needs some grease, after 20 years of mowing in the Texas summer.

Electric Riding Mower Direct Drive Test

I was been simultaneously itching to try out the new direct drive on the riding mower project, but also a bit afraid. It something burned up or broke, I was probably finished. So I promised myself I would do it right and reassemble the whole back end and put in a proper kill switch. And I was distracted with the blades.

I decided at the last minute to keep the big blade height handle. I figured out a way to connect it with the new motor set up. Hopefully I will be able to use it to control the blade height. At this point I am happy with the motor and the electronics. I will post a video in the next posting.

Electric Mower Design Decisions

I feel like I’m getting to the end of this one, at least the 1.0 release. There are a few pieces left.

Shifter: the shifter is large and probably over designed. All it does is push a small rod into the transaxle to change from forward to neutral to reverse. With an electric motor, this isn’t really required. The motor is easily turned off and even reversed. All that said, it isn’t in the way and it could be useful, for instance, to put the transaxle into neutral. Tempting to take the mechanism down to simplify things but it will stay, for now.

Brakes: there is a brake lever on the transaxle very near the shifter. In the photo it is connected to the spring. This is connected to a rod and to the large pedal. This pedal was a combination brake and clutch and had some complex mechanical and electrical interlocks to the old blades and engine. The pedal works well enough but needs some springs to keep it in place. Looking at repurposing some of the old springs. Will also have to put in a stop using a bolt. My other concern is braking with the motor engaged. It is possible to mount an electrical switch to turn off the motor when the brake is engaged. We will see if that is necessary in practice.

Blade Height: the metal bits are the original blade deck lift mechanism. I intended to use it, even though it was overkill, but the mounting of the motor made me take it down, piece by piece. I may yet use some or all of these pieces and mount points to control the mower blade height, but this is still open. Perhaps the last open design issue.

Electric Mower Blade Test

The blades are just some 24V scooter motors with heavy duty weed whacker blades mounted on them, all mounted into some 2″ PVC pipe. Wired it up using my fancy new WAGO lever nuts and hooked it up to the new controller. Need to put in a safety cover and figure out the mounting and lift mechanism but it looks up to the job. Still haven’t ridden the direct drive yet. Going in a few different directions at once.

Mower Rework

Installed the replacement controller for the blades. Still no idea what happened to the old one. The new one doesn’t have an LED display, which I really don’t need. I was tempted to leave the switch out, too, since the speed knob also is an on / off switch, but decided to leave it in. Easier to reverse the blades, which are sharpened on both sides. Had to cut some new plastic for the dash, but I am getting good at that. I also realized that my kill switch is “normally open”, the opposite of what I need, so I ordered a new one.

On test I heard a pop and smelled something burning. Damn. I had wired the new controller battery outputs to the motor terminals. It was labelled in only Chinese, but it matched the old one and I could read the English on the circuit board underneath. Totally my fault. Seems I blew a 30A fuse on the battery cable that I put in just for extra safety. I am becoming a big believer in safety.

Swapping the fuse, the motor controller still works, but haven’t hooked up the blades to see if I damaged anything. Also been studying the brake and the blade deck lift mechanism. Both are big and heavy and complicated. Going electric simplifies just about everything but now I need to re-invent the lift and the brakes. Oh, used some of these German wire connectors. No reason to go back to wire nuts. I’m told to be careful and buy the real German product and not cheap knock-offs.

Electric Riding Mower Blades Dry Fit

Found the nice little 24V 30W motors that fit exactly inside of a 2″ PVC pipe. Took me a while to get around to it but cut and dry fitted the pieces to see how it looks. Bolted on these string trimmer replacement blades that are available from all sorts of vendors for a wide range of prices. Went for the least expensive ones, at $7. I was going to use the same controller as the one for the main motor, but somehow, after I had fully installed it, it turned up broken. So I ordered a simpler replacement controller. I really don’t need the LED readout.

Will glue it all together and wire it up another day. I still need to figure out how to hook in up to the original blade height mechanism. I removed much of it because it was made for a different platform that was maybe 70 or 100 lbs of metal. Looking for a simp!e soultion (as always). Also need a safety cover. Looking at some pie pans, which are metal, but instead might go with some of those shallow plates that go under flower pots. Plastic and easier to work with. Everything is smaller and lighter so no real need for a massive deck. Just something to prevent dumb accidents.

Electric Riding Mower Drivetrain 2.0: Direct Drive

I finally got around to experimenting with replacing the slow and unreliable chain drive with direct drive. The metal plate supporting the motor came from the front someplace and fits perfectly. I was worried about aligning everything. With six or so degrees of freedom and me with a hand drill, it seemed beyond my abilities. I learmed a trick: drill big holes and use bolts and adjust and tighten up as you go along. The old fenders even fit. Heck, if I went with an expensive lithium battery there would probably be room for it in the back, too. It seems a bit noisy but I’m guessing the 20 year old transmission could use some grease. Unfortunately there isn’t a simple way to do this. I will have to take the whole transmission housing apart. Maybe at some point.

Funny, all the effort with chains and sprockets seems like a waste, but I guess that is prototyping. You try stuff out and try to hop from A to B. Sometimes it works, sometimes it doesnt. Will give it a ride tomorrow of the next day. It’s going to be fast and lots of torque. Will probably hook up the deadmans switch first. Maybe wear a helmet.