# Electric push mower



## onesojourner (May 6, 2008)

My mower is about to die so I am seriously considering switching it to electric. Would 24 volts be enough? Does any one have a motor suggestion for this application? I also would need some thoughts on a controller. I don't know that I would need anythign complicated. I will just need the motor to spin up to its most effecient rpm and stay there until I am done. I have not found many people that have done this just a few pictures on the web.


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## ElectriCar (Jun 15, 2008)

This may do the trick. Since 1 HP = 746 watts, this one rated at 480w is just over 1/2 hp. However electric HP is supposedly 8-10 times more powerful than a comparagle gas engine. Therefore you've got about 4HP gas equivalent here. It should be all you need. 

Just don't know what type batteries to suggest as I'm a noob in this foray myself! Keep us posted though.


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## dimitri (May 16, 2008)

This thread had a good start, there is a link to a nice 1 HP motor from beepscom.

http://www.diyelectriccar.com/forums/showthread.php?t=13240&highlight=mower

If you look at commercial model mentioned in that thread you will see they use 36 V , similar sized motor. I would not go for anything smaller, because it will choke on tall grass. 

I wanna convert my John Deere self propelled push mower, so I need some power for the wheels as well as cutting.

Anything higher than 1 hp becomes very expensive, not worth the trouble.

As for batteries, I think 3 small 12 V batteries for riding lawn mower or motorcycle should be good enough to provide juice for an hour.

This will be my next project after I finish my Miata conversion.


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## ElectriCar (Jun 15, 2008)

Oops, yesterday when I posted the reply I didn't insert the link.  Oh well, here it is. http://cgi.ebay.com/DC-Motor-Speed-...ryZ71393QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Long link! But this will only handle a 1/2 HP motor I believe, based on it's 480Watt rating. I haven't evaluated the thing as to it's specs other than what's posted so that would have to be checked in to.


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## dimitri (May 16, 2008)

I wouldn't bother with controller at all, just on/off switch with proper amp rating. After all, do you throttle your gas mower? I don't, I just run it at max speed anyway.


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## ElectriCar (Jun 15, 2008)

My last push mower had a fixed throttle, which I hate with a passion! I suppose that was an attempt to save a dollar by mower companies. 

Regardless of their reasoning, my lawn doesn't require pedal to the metal power to do, even when overdue. So in my case it's a waste of energy. In that case, for that dollar they saved omitting a throttle cable, it's probably cost me another $50 in wasted fuel.

But you're right, it would work without a controller if need be.


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## onesojourner (May 6, 2008)

How would you keep the motor from spinning to the moon with no controller. You would have to have something to keep things in check wouldn't you? I have a borrowed mower for the summer so I can focus on getting this done over the winter. 

I do use a throttle on my mower, sometimes. I could live with out it though. I have a fairly small yard. it Takes around 30-40 minutes to mow the whole thing.


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## dimitri (May 16, 2008)

onesojourner said:


> How would you keep the motor from spinning to the moon with no controller. You would have to have something to keep things in check wouldn't you?


I was planning to use the relay controlled by a microswitch at the handle, release the handle and it shuts off the power.

This would provide adequate control I think. While cutting the grass I would not worry about the RPM, the grass will slow it down well, hopefully not too much


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## onesojourner (May 6, 2008)

dimitri said:


> I was planning to use the relay controlled by a microswitch at the handle, release the handle and it shuts off the power.
> 
> This would provide adequate control I think. While cutting the grass I would not worry about the RPM, the grass will slow it down well, hopefully not too much


What about when you lift the mower up or when you hit a spot that you have already mowed or when its august and the grass is pretty thin in some spots. I think there would have to be some kind of speed control on there.


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## Nodd (Jun 6, 2008)

If you're planning to convert your mower to electric to save gas & the environment then you might want to consider a human powered reel mower instead. Something like this...









I picked up one of these a few months ago & was amazed at how well it worked. Most folks think they're hard to push but just the opposite is true. Because there's no motor they're pretty light. In my opinion they're easier on your back than a standard mower.

If on the other hand you're doing this conversion for fun or for the challenge then I say go for it. Good luck.


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## onesojourner (May 6, 2008)

Nodd said:


> If you're planning to convert your mower to electric to save gas & the environment then you might want to consider a human powered reel mower instead. Something like this...
> 
> 
> 
> ...


I have actually considered that rout. It is basically going to come down to price. If I go with the reel mower I will most likely have to borrow a powered mower in the fall and maybe some in the spring.


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## Telco (Jun 28, 2008)

I tried the reel mower, but found them to be crap. At least, the ones from Home Despot are. The ones I had (repeated returns) kept jamming up due to cheap pot metal parts bending and warping. If you've found a good, sturdy one, please post the brand and where you got it. My current yard is VERY well suited for a people powered reel mower.


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## Nodd (Jun 6, 2008)

I got mine at Lowes for $90 & its been going strong all season. Lowes sells a couple of models, one 16" & one 20". Both have options for a clippings bag. Here's a link to the model I'm using:

http://www.lowes.com/lowes/lkn?action=productDetail&productId=227682-53393-26113&lpage=none

One thing I did notice about reel mowers is that they don't handle debris well. If your lawn has a lot of stones & twigs they can tend to jam the blades. But if its a fairly clean lawn they work great.

Anyway I don't mean to hijack this thread & turn it into a discussion about reel mowers. I just wanted to offer an alternative. Back to electric mowers...


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## Deekman (Jun 29, 2008)

onesojourner said:


> How would you keep the motor from spinning to the moon with no controller. You would have to have something to keep things in check wouldn't you?...


DC motor RPM ratings are usually for no load. So if you have a 2000 RPM motor, and put full voltage and no load on it, it will spin to 2000 RPM.

Add a heavy, high-pitch lawnmower blade to the equation and things will slow down considerably.

-Deek


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## lordtimothy (Jul 18, 2008)

Bear in mind that lawnmowers are designed to be ran at max throttle settings. If you slow the blades down you are going to lose some of your cut quality. What I feel would be the best solution is to have a one speed mower and design everything around that principle.

Timo


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## ElectriCar (Jun 15, 2008)

Anybody pushing one in Zoysia? That stuff is best cut with a reel mower but it's so thick I bet you can't do it without a motor.


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## onesojourner (May 6, 2008)

I have had a rough summer and haven't made any progress on this yet. I am still trying to figure out if I can get by with no controller. I also learned that the battereis from the commercially available electric motors are for sale. You can get them in 24 and 36 volt configs and they are light. They are still lead acid though.


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## 1clue (Jul 21, 2008)

I just found this thread, so sorry if I bring things up that were dropped earlier.

I'm a n00b at EV conversions, so some of what I say might be stupid for that reason, and the rest might be stupid for some other reason. 

At first, somebody (not on a forum just someone I know) suggested a lawn mower conversion and I laughed it off as a waste of time. Now I'm not so sure.

Speaking to the human powered mower, I have one too. I found it while helping a friend's grandfather clean up a farm that had been lost due to a highway going through. It's an antique, but it's solid. I've also tried one of the newer ones and agree that they're junk. I have heard that you can get a high quality human powered mower, but they cost about as much as a gas powered one so you gotta be a real bunny hugger to buy one.

My HP mower also jams up on sticks and rocks, both of which abound on my property. It can chop through the tiny twigs, but nothing over about 1/8 or it jams up. You can't wait too long to mow either, or it just walks over the grass rather than cutting it. However, when it's got a clear shot, it is much easier to use than a self propelled gas mower. Enough so that I wonder why gas mowers ever caught on for small lawns.

One thing that comes to mind it to use a 1/4 horse motor to spin the cage and then just push it.

As well, a conversion from an ICE mower seems to be a good practice or test bed for a car conversion.

So, I might wind up with an AC or BLDC motor on a mower....


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## oldtimer (Jul 30, 2008)

As I recall my youth with a HP push mower, you had to really keep the blades sharpened and lubricated for tall grass, also, you could improve cutting ability by raising or lowering height of handle while pushing. Haven't tried in 50 yrs or so, and not interested in renewing my acquaintance with one, new or antique, either.


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## TX_Dj (Jul 25, 2008)

First of all, corded electric mowers are rather inexpensive. Comparable in price to gas. But, they tend to have narrower decks than the same price gas mower.

It doesn't seem that anyone makes them like they used to anymore, though. Used to be that the handle was mounted in the center so you could flip it from end to end, pushing it both ways. This was handy, because you'd point the discharge chute towards the curb and have the cord coming from the house... mow one swath, flip the bar and mow the next swath, with the cord always being on one side, and the clippings getting thrown closer and closer to the curb, making it easy to collect and bag, if you're into that sort of thing. These days, the corded mowers seem to have lost this function, giving owners a hassle dealing with the cord so they don't mow over it.

Ten years ago when I started working on my first EV conversion, my mower died. I was sick of dealing with ICE anything, so I went shopping for a little corded mower like my Pop had when I was a kid, and found they'd made the change where you couldn't flip the handle and didn't want to mess with the cord.

Around the same time, Black & Decker came out with a cordless mower. I thought to myself that it was a perfect complement to my EV conversion project, so...

10 yrs ago, I bought this thing (mine's green though):









The first pair of batteries lasted 5 years, and I'm nearing the need to replace the second pair of batteries. The batteries cost about $60/ea, so if you figure that the average ICE mower tends to die within the first 5 years and replacements cost $120, then this is just as "economical". 

You can have one today for only about $300. It bags, mulches, and can be configured for discharge as well.

Granted, it doesn't have enough juice to mow tall grass, but most of us looking for an e-solution for mowing are probably not the type to let the grass get too tall. It doesn't have enough runtime to mow huge yards, but it does have enough to get the job done.

Love mine, wouldn't trade it for anything other than another.


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## 1clue (Jul 21, 2008)

TX,

By "huge yard" what do you mean? Will it mow a quarter acre? And is it self propelled?


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## TX_Dj (Jul 25, 2008)

Not self-propelled, but also is mostly composite and plastic, so it's very light weight. Even with big sealed lead acid batteries in it, I think it weighs less than a super-cheapo ICE mower. Not sure how it would fare on a 1/4 acre. Its capacity in my experience is about equivalent to a small ICE mower's gas tank, actually more... the house I lived in at the time I bought it would require about 1.5 tanks (tiny) on the little 3.5 horse briggs mower I had, and the cordless would do the whole thing on one charge with energy to spare.

My lot isn't huge, but I also tend to be lazy about mowing and let it get a "little" long before I cut, and until about mid-summer this year, I could rip the front and back lawns without even diving into the "yellow" on the idiot-voltmeter. Now that the batteries are slowly giving up the ghost, I dive into the yellow more often, with some of the more overgrown stuff taking a short stab at the red. The batteries are dying, nothing will make em better, so I'm treating them as gentle as I can while still getting the job done. Expect that I'll have to replace them next season.


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## TX_Dj (Jul 25, 2008)

Just looked on B&D's site... they claim 1/3 acre (minus driveways, sidewalks, flower beds, etc) of 10,000-12,000 sqft is the ideal size for the mower. Also seems they claim it has an MSRP of $450 now. Checked Lowes and Home Depot, and can't find it listed on their site, but I bought it from one of those places.

Even if I had to go out and spend $450 to replace it, I'd have no qualms about it, though this looks like it's a newer model, the handle is a little different configuration and the cowl over the motor and batteries looks a little different shape. May use different battery chemistry, but didn't see anything to say...

They also claim it weighs 76 lbs and "may be hard to push up steep hills". I guess that's about right- most of the weight of the thing is in the batteries and motor. I find mine easier to lift into the back of the truck than my friend's gas mower, which is an all-steel ICE cheap-o.


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## Shanex-2 (Jun 7, 2008)

has any one tried an air or flyweight governer controling a microswitch that turns on and off a contactor at a pre set rpm. that way under light or no load it wouldn't fly apart. it would be simple and easy to build.


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## Shanex-2 (Jun 7, 2008)

here is a drawing of what I mean sorry my drawing skills on a computer aren't great but it will give you an idea. 
On top of the motor is a cintrifigal fan which blows air against the governor arm . when it moves enough air to overcome the sping pressure it would break the circuit and the contactor would shut off untill the motor slows down alowing the micro swich to connect again energizing the contactor .all you need is to get the right spring for the desired rpm.


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## xrotaryguy (Jul 26, 2007)

Someone said that some gas mowers are fixed throttle. Actually, all gas mowers have an automatically adjusted throttle that keeps the rpm pretty constant. The setup also keeps the engine from being damaged from over revving. 

Whether or not you would NEED a speed controller on an electric... I don't know


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## JRP3 (Mar 7, 2008)

If you size the motor and battery pack properly you should need no speed controller. Say you pick a motor with a free speed of 4000rpm at 48 volts, then run it at 36 volts, or something along those lines. You'll never have to worry about over revving the motor. Or as has been mentioned once you stick a blade on the end of the motor you're not really ever running it unloaded.


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## TX_Dj (Jul 25, 2008)

And that's a good point, JRP3.

Once you have the mass of a long blade on the end of the motor, it has something "to do" when it's not cutting. 

Considering I recently burnt up my weed eater by running my line length too long, one must really consider the motor and blade weight/length carefully to come up with a good combo, IMHO. If the motor is chewing amps just trying to keep the blade spinning while cutting a short lawn, you'll end up generating more heat than the motor's fan can extract, and "That's not a good thing."

For the record, the B&D cordless mower I was talking about does not have a speed controller. Instead it has a thermal cutoff and a regular circuit breaker, both are auto-resetting. If you jam the blade and don't release the safety handle (manual cutoff) soon enough, the circuit breaker will trip. If you're too aggressive trying to cut too tall grass too short, the thermal cutoff will trip.

Otherwise, you just get a on/off control. The motor will automatically suck more amps at lower speed and let the volts come up at higher speed just by the nature of the thing.


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