Solar Lawn Mower!

Let's go green!
I've had battery powered lawn mowers before and the biggest problem I've had with them is keeping them charged. You have to either plug them in or take the battery out and that sucks.
This is one solution to the problem. Install solar panels on the mower and just leave it parked in the sun to charge it.
Here's how I did it!

Step 1 Tools and Materials Needed

Tools

• Soldering iron
• Wire stripper
• Volt meter
• Screw driver
• Wrenches

Materials

• Battery Powered Lawn Mower
• 2 - 12 volt Photovoltaic Solar Panels
• 4 - General purpose rectifier diodes
• Double-stick tape
• Nuts, Bolts & Washers
• Solder

Comments

[patenaude]

I'd be worried that if you left it out for long periods (weeks->months), that the panels would eventually cook the batteries.

[Marsh]

time will tell.

[sbeazley]

Let us all know when/ if that happens. Would be good info.

[9w2xyz]

nice. Did the same thing with my truck. Came back to see the panels stolen. At least they left me the diodes...... pfffftttttt....

[wirecutter]

Nice device but you only need ONE diode on each cell ( it is a series connection you can redraw it with the two diodes connected next to each other) as with two in Circuit you lose about 1/2 a Volt and that in the UK's sun is important in giving you a charge in to the battery. ( Image = 2 diode ) Even better is to join the positive of one panel to the negative of the other battery get rid of the junction to the middle of the batteries and then you only need one diode in the circuit and you are charging at 24 volts ( Image = 1 diode ) ++++++++++++

[kill-a-watt]

ayup. both will work fine. First will charge even if the sun blocks one of the panels (though only one pair of batteries will charge), and the second will avoid a drop of six tenths of a volt by removing one diode.

[lbrewer42]

Goats work well for lawnmowers :^)

[Marsh]

No they don't. People fall in love with them and start feeding them Barleycorn and molasses. From that point on, they stop eating grass.

[static]

That's a people problem, not a goat problem. :)

[blained]

Only because barleycorn and molasses-fed goats TASTE better.

[kill-a-watt]

this wouldn't last a week in my backyard unless locked in the shed.

[Marsh]

Ever consider getting a dog?

[kill-a-watt]

yes, but not for the sole purpose of guarding my lawnmower vs. locking it up.

[Marsh]

Ask any cop. The general consensus is that people who have dogs don't have their stuff stolen from their back yards. Even if it's just a yappy little rat-dog. You could always mount the PV panels on the roof of your shed and set it up to plug in when you park the mower inside. The kit I used must have come with 20' of wire and I re-used the plugs in the project.

[xenor]

Someone stole a bag of dog food from my backyard (even when guarded by yappy chihuahua)

[thebriguy]

...or add a car alarm (haha:-)

[Captain John]

Would this mower work on the solar cell alone, or is a batery needed? I guess you can just park it in the sun and operate of the battery. Will the charging stop if the battery is fully charged?

[vmod32]

lol... no way it would run off just the solar panels.. I think you have a major misunderstanding about how much power solar panels produce. Those panels could hardly power an MP3 player, never mind a lawn mower

[Marsh]

These panels keep the batteries charged and ready all of the time. They're not very powerful. They probably won't overcharge it.

[vmod32]

Exactly, they just slowly charge the batteries. Very slowly since there are a lot of batteries. If you have a small lawn that does not need cutting very often, they may provide enough juice to never have to plug in the mower. Or at least extend the time between needing to plug it in. But there is no way the panels could power the mower without the batteries. They probably provide 1/1,000 of the power the mower would need to run. But store up all that power over several days in the batteries and your running the mower.

[luvit]

you mow dirt, like me. you are full of awesome. i also mow my trash.. you?

[EmmettO]

I was going to say, "Of course the solar panels are enough to mow your lawn! I don't see any grass!" Just kidding though. Lawns are evil. I try to kill mine as much as possible by putting in gravel play yards, gardens and a big pit that is supposed to be a workshop one day.

[Marsh]

They had a program in Phoenix a few years back where they paid you to tear out your lawn and replace it with gravel. Now grass grows through the gravel and you can't get on it with a lawnmower because you'll break your windows with the flying rock. What a cruel joke! LOL!

[EmmettO]

We put down that black weed barrier fabric before putting down gravel and it's held up well. Weeds will root on the rocks themselves, but they're few and easy to pull out. Also if you're not chemical squemish, a $14 jug of round up goes pretty far. I tried avoiding it but when my driveway started to sprout plants that will kill my wife (allergic) I got a jug and went to town on all the places that I'd been trying to suppress weeds mechanically.

[Marsh]

I actually have a lawn out front. Now that I have a mower, maybe I'll put one out back too.

[luvit]

whoa! people can have 2 lawns? i wonder if rich people have side lawns..

[RaNDoMLeiGH]

Stupid people have side lawns. (What were we thinking?!) We had a sidewalk and a driveway that also needed mowing, because they were very old and full of cracks.

[TinkerWorkshop]

Would it be possible to get the schematics of the full circuit? You have a small schema of the "solar battery goes here", but you lost me with the cigarette lighter circuit.

[Marsh]

The full circuit is there. This unit doesn't use the cigar lighter plug. It was only shown to indicate the voltage regulator contained within...which we did not use.

[TinkerWorkshop]

Ok then I am unconfused. Thanks! Would it be possible to run a cost approximate? mostly I am asking about the land-mower.

[Marsh]

It's pretty comprehensive and all of the info you're looking for is there. Some of it is only on the photo notes so be sure to look at all the pics and mouse-over to read the associated notes.

[talonts]

A few comments: 1 - The wiring could be cleaner/shorter if you rotate every other battery in the pack, so the +- jumper is very short. 2 - most solar panels have diodes built into them to avoid reverse flow already - if your panel screws together, open it up and check it before wiring. 3 - I'd recommend using Velcro to hold the panels on when not in use, and removing them while cutting - panels aren't really designed to be bounced around on a mower, even the ones made for charging cars. The shocks from occasionally hitting rocks or twigs will shorten the life of the panels. Better to remove them while in use. It also allows putting the panels in a better location for sunlight, as you noted in comments later. 4 - if you make the panels removable, cut the plugs from the panels, and use a 4-pin Molex plug to attach both. Molex plugs (ones with release tabs) will come apart easier than the plugs the panels in the 'ible have.

[Marsh]

Connecting and disconnecting are precisely what I want to get away from.Keep checking back. I'll post updates when it dies or develops any problems.

[thebriguy]

You might consider a charging pad you just push the mower into and it charges - Either plugging it in when you push it in or make the contacts somewhere underneath so when it's positioned right on the pad it charges. Just some ideas. Thanks for the 'ible.

[rhackenb]

I have this Toro mower. I've gone through two sets of batteries over 5 years. When I need to replace the batteries, I buy them from Toro. Instead, I get two 12 volt batteries from Batteries Plus or some other dealer. The cost is usually around $100 for the pair. I glue the batteries and wire them in series so that I get 24 volts. You say that the batteries you get cost $18. I wonder what the physical dimensions are and the amp hour rating. The two batteries that I use fit perfectly into the mower without any extra space. The batteries you use must be thinner. I appreciate the detail you have gone to in designing this. It taught me some lessons on electrical design. However, I'm not sure if the purpose is to charge the mower without having to plug into a wall outlet. If that's the case, a much simpler solution might simply be to plug the solar panels into an inverter and then plug the mower into the inverter. We actually use this solution to charge other battery powered devices such as drills at a shed we have that is not connected to the grid. See http://www.instructables.com/id/How-to-mount-a-solar-panel/.

The real benefit to me would be if the solar panels actually extended the current charge of the batteries while I am mowing.  Do you think these two panels would be sufficient to extend the charge in any meaningful way.  For example, could I mow an additional 30 minutes?   If not, the downside of the design is that the extra weight of the panels will make the mower even heavier to push.

Very good instructable.

[Marsh]

The replacements I used are made by Powersonic and they are exactly the same size and rating as the ones that came out of it (presumably the originals.) The idea was that I would never have to plug it in. I just park it on the back 40 and it's ready any time I need it. It runs for well over half an hour even if the grass is wet. I mean, I'm done in 25 minutes and the charge indicator is still reading full. Your batteries should last longer than that. They're probably being over charged by the on-board charger.

[RaNDoMLeiGH]

I appreciate the trouble you took to take pictures at each step. Even though I've had some experience with circuitry, I still sometimes get brain farts. Haven't fried anything in a while, but when I was rewiring my rain lamp late one night I had a mo where I lost track of what was what and had to trace a wire back. Duhr. Pictures GOOD for Thag.

[Kinnishian]

This is an awesome design. But I thought solar cells are fairly delicate? Do you think they will put up with the vibrations of a lawn mower?

[Marsh]

Electric motor are nowhere near as shaky as a gas engine. These are pretty tough and waterproof. They should hold out.

[nabo00o]

I agree with wirecutter, and also just a minor mistake, electrical potential is measured in volts, not watts. Watts is power, and is the product of volts and amps.