# Tell me why I'm getting the wrong self propelled electric mower



## Lawndress (Jul 9, 2020)

I have .75 acres of grass. I have a gas rising mower but am getting an electric self propelled back up. Want it under $850. This is what I'm considering: https://www.homedepot.com/p/Greenworks-PRO-25-in-60-Volt-Cordless-Battery-Self-Propelled-Walk-Behind-Lawn-Mower-with-2-4-0-Ah-Battery-and-Charger-MO60L427/315447054

Please let me know if I'm making a terrible mistake.


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## PodScot (Mar 18, 2021)

For that price why not get an Ego? They seem to be the king of cordless yard tools right now across the board - mower, blower, trimmer, etc.


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## Lawndress (Jul 9, 2020)

PodScot said:


> For that price why not get an Ego? They seem to be the king of cordless yard tools right now across the board - mower, blower, trimmer, etc.


I already have chainsaw, blower, hedge trimmer, and string trimmer in the Ryobi 40V ecosystem and 2 batteries. Went into it before Ego existed.

But the Green works is 25". My yard is .75 acres. 4" matters enough to go into a different ecosystem for which I have no tools.


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## MasterMech (Sep 24, 2017)

Are you mowing the whole lawn with this? I'd be worried that it just wouldn't have the endurance needed to do that efficiently on on over 32,000 sq ft of turf. If you have to stop to charge or buy a second set of batteries, that would be a deal-breaker for me.

I do wonder how the 25" machine differs from a 21" machine in terms of energy efficiency. My first reaction is that there's no way swinging two 13" blades is more efficient than swinging a single 21/22" blade. But I don't know about the aerodynamic effect and how much drag each blade produces. I can only assume that with similar blade tip speeds, we're making nearly 2x the drag a single blade design would and that losses from running a second motor/spindle are minimal. With a battery powered unit, this is significant as it would noticeably reduce runtime. Both Greenworks units (the 21" and 25") quote similar runtimes on the same size batteries. I wonder how that plays out on actual turf.


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## Automate (Aug 14, 2020)

I would think if everything else is equal, the 2 blade mower would be more efficient. Aerodynamic drag goes up with the cube of the speed. So while the inner part of the bade is going as slow as it can and still get a proper cut, the outer part of the blade is going faster than required. This extra speed on the outer parts of the blade are using up energy at a rate raised to a power of 3 of the speed difference.


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## MasterMech (Sep 24, 2017)

Automate said:


> I would think if everything else is equal, the 2 blade mower would be more efficient. Aerodynamic drag goes up with the cube of the speed. So while the inner part of the bade is going as slow as it can and still get a proper cut, the outer part of the blade is going faster than required. This extra speed on the outer parts of the blade are using up energy at a rate raised to a power of 3 of the speed difference.


In a mower, you need the blade tip speed to be above a minimum threshold to make an acceptable quality cut. The outermost portion of the blade is doing the vast majority of the cutting work while the inner portion is doing almost no work. So in order to maintain the cut quality, you have to spin a smaller blade faster than a larger one.

Typical example: 21" mower swings the blade at 3,200 RPM

5.5' circumference means the bale tips are moving at 17,600 FPM

To get a 13" (3.4' circumference) blade tip moving at 17,600 FPM, the spindle speed must be raised to 5,176 rip 'ems.

You'd also be dragging 4 sails through the air vs 2. So how much drag is there swinging 4 sails that are half the size of 2? I dunno but I'd venture a guess that it's more energy to run overall. There are other variables at work here too as the shape of the deck must change with the 2 blade design and this means that the blades are no longer fully shrouded.


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## Lawndress (Jul 9, 2020)

MasterMech said:


> Are you mowing the whole lawn with this? I'd be worried that it just wouldn't have the endurance needed to do that efficiently on on over 32,000 sq ft of turf. If you have to stop to charge or buy a second set of batteries, that would be a deal-breaker for me.
> 
> I do wonder how the 25" machine differs from a 21" machine in terms of energy efficiency. My first reaction is that there's no way swinging two 13" blades is more efficient than swinging a single 21/22" blade. But I don't know about the aerodynamic effect and how much drag each blade produces. I can only assume that with similar blade tip speeds, we're making nearly 2x the drag a single blade design would and that losses from running a second motor/spindle are minimal. With a battery powered unit, this is significant as it would noticeably reduce runtime. Both Greenworks units (the 21" and 25") quote similar runtimes on the same size batteries. I wonder how that plays out on actual turf.


I can actually borrow my neighbors' extra batteries because they already have a greenworks mower and I often mow their lawn with my riding mower.

This is a supplement to the riding mower, except when it is in the shop. That happens too often, I'm afraid. I don't know how much I'll like the walk behind, but when the weather is nice, there is a good chance I'll choose it because it will be a nice mild walk.


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## Lawndress (Jul 9, 2020)

MasterMech said:


> Automate said:
> 
> 
> > I would think if everything else is equal, the 2 blade mower would be more efficient. Aerodynamic drag goes up with the cube of the speed. So while the inner part of the bade is going as slow as it can and still get a proper cut, the outer part of the blade is going faster than required. This extra speed on the outer parts of the blade are using up energy at a rate raised to a power of 3 of the speed difference.
> ...


Anyone care to measure the moment on the end of a cutting blade, based on its length and the force exerted by the grass? Lol.

I have no clue which would be more efficient. But Greenworks does something other mowers don't and drains one battery at a time. With four batteries and two chargers, I should be able to pretty much mow continually.


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## MasterMech (Sep 24, 2017)

It sounds like you may a little adverse to gas-powered maintenance, but one of these mowers, at the sale price, and two extra 4.0aH batteries is $900 worth of equipment. $1,050 without the "sale".

That puts it awful close to the Toro Timemaster 30" walk-behind at $1200, $1300 if you want the electric start version. In my mind, the only area the Timemaster would not send the Greenworks back to the shed would be noise, and the occasional oil change.

I can certainly empathize with you if you just want to avoid gas, as I'm kind of in the same boat with my handheld equipment desires. Without borrowing your neighbor's batteries however, (and is that a permanent arrangement?) I just don't see this machine making sense for this application. The 10 year cost of ownership for the Timemaster would almost certainly be lower while delivering superior results.

If the money is no issue, and you dislike dinosaur powered equipment, shoot, there are battery-electric riding mowers in the $3-$5k range that might take the place of your existing riding mower and you could continue with the Ryobi 21" as a trim/walk mower.


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## rbvar (May 28, 2020)

For those times when you'll be using the push mower, Is mowing the entire lawn in one go important to you, or not a factor? If you don't mind breaking things up, like a before lunch/after lunch mow, then the battery recharge issue is moot. Then the 25" Greenworks seems fine.


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## g-man (Jun 15, 2017)

My back neighbor has one and a gas one for a 7k lawn. The batteries dont last to do the entire yard, hence the gas one.

Another factor is that with freshly charge batteries, it cuts ok. But as the battery wears, the blade speed drops and the quality of the cut drops. In the spring flush with a moist lawn, it really struggles to keep the blade speed. I think the motors they are using dont have enough torque (cost saving? weight?). But you can really mow at night without waking up all the neighbors kids.


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## Retromower (Jan 28, 2021)

Id personally go Ryobi over Greenworks or Ego because you cant beat it for the value and replacement batteries are readily available. Not to mention if you ever wanted to expand into other tools, Ryobi has a big selection of 40v tools and an even bigger selection of 18v tools.


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## ADanto6840 (Apr 1, 2021)

+1 on Ryobi. I'm a big fan of their tools in general. I actually loved their 18V brushless mower (non self-propelled), though I picked their 40V brushless self-propelled version on OfferUp for $65 a few months back (without battery). Since I'm already in the ecosystem it was a no-brainer, but I'm thrilled with it thus far.

That said, I wish Ryobi offered a reel option in the US. They have one in AU, and you *could* import it for a total of ~$450-ish, but it's unclear how well it actually performs and warranty might be questionable on an import. Since I'm going Bermuda in my backyard, I may end up picking up a reel or greens mower, we'll see. I'd love to buy an electric reel but the options seem relatively few & mediocre, at least at this point.


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## Lawndress (Jul 9, 2020)

MasterMech said:


> It sounds like you may a little adverse to gas-powered maintenance, but one of these mowers, at the sale price, and two extra 4.0aH batteries is $900 worth of equipment. $1,050 without the "sale".
> 
> That puts it awful close to the Toro Timemaster 30" walk-behind at $1200, $1300 if you want the electric start version. In my mind, the only area the Timemaster would not send the Greenworks back to the shed would be noise, and the occasional oil change.
> 
> ...


It is entirely a permanent arrangement. I do their leaves for free every year and a lot of the weeding in their front bed. And I mow their yard more than they do. I'm BFFs with the wife and friends with her husband.

I am keeping my monster gas-powered 52" riding mower....for now. It's definitely overkill now that I have so many flowerbeds! But it's amazing when the leaves all drop on the shady lawn and I can't mulch anymore. Plus, pedal to metal, I can kill a mow in less than 20 minutes, neighbor's lawn too, when I'm in a crunch. It was $3k with accessories back on the day, and the riding mowers have expensive battery issues more than the walk behinds. Every gas engine I chuck though is a delight to me since it's that much less maintenance.

I actually have an aversion to the noise of gas mowers. I known that's weenie, but it's just not something I like, and it makes lawn work less fun. I haul things in a wheelbarrow rather than my tow behind dump cart, as it is. So if the walk behind is more fun because it's quiet, I'll be using it a lot more.


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## Lawndress (Jul 9, 2020)

Retromower said:


> Id personally go Ryobi over Greenworks or Ego because you cant beat it for the value and replacement batteries are readily available. Not to mention if you ever wanted to expand into other tools, Ryobi has a big selection of 40v tools and an even bigger selection of 18v tools.


I already own every single Ryobi 40v tool except the mower. I just like the extra 4" on the Greenworks.

The chainsaw isn't as good as I thought it was. I'd ditched my others after using it to saw a bunch of softwood. Then I tried it on hardwood and realized I had made a mistake. Took less time to cut it with a handsaw, and I'm a 40 year old chick.


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## Lawndress (Jul 9, 2020)

ADanto6840 said:


> +1 on Ryobi. I'm a big fan of their tools in general. I actually loved their 18V brushless mower (non self-propelled), though I picked their 40V brushless self-propelled version on OfferUp for $65 a few months back (without battery). Since I'm already in the ecosystem it was a no-brainer, but I'm thrilled with it thus far.
> 
> That said, I wish Ryobi offered a reel option in the US. They have one in AU, and you *could* import it for a total of ~$450-ish, but it's unclear how well it actually performs and warranty might be questionable on an import. Since I'm going Bermuda in my backyard, I may end up picking up a reel or greens mower, we'll see. I'd love to buy an electric reel but the options seem relatively few & mediocre, at least at this point.


If I start doing a reel mower on .75 acres, after all the flowerbed work, you will know I've lost my mind.


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## Retromower (Jan 28, 2021)

Lawndress said:


> Retromower said:
> 
> 
> > Id personally go Ryobi over Greenworks or Ego because you cant beat it for the value and replacement batteries are readily available. Not to mention if you ever wanted to expand into other tools, Ryobi has a big selection of 40v tools and an even bigger selection of 18v tools.
> ...


It seems to me like the Ryobi mower is a no-brained then. If nothing else, its worth it just to get another 40v battery.


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## Retromower (Jan 28, 2021)

ADanto6840 said:


> +1 on Ryobi. I'm a big fan of their tools in general. I actually loved their 18V brushless mower (non self-propelled), though I picked their 40V brushless self-propelled version on OfferUp for $65 a few months back (without battery). Since I'm already in the ecosystem it was a no-brainer, but I'm thrilled with it thus far.
> 
> That said, I wish Ryobi offered a reel option in the US. They have one in AU, and you *could* import it for a total of ~$450-ish, but it's unclear how well it actually performs and warranty might be questionable on an import. Since I'm going Bermuda in my backyard, I may end up picking up a reel or greens mower, we'll see. I'd love to buy an electric reel but the options seem relatively few & mediocre, at least at this point.


I love my Ryobi One+ 36v. For my 3,000 square foot yard, its perfect. Ive read some bad reviews of the new One+ HP 18v mower, mostly to do with battery life but if my 36v died tomorrow, Id go out and buy a One+ HP 18v without a 2nd thought.
Hopefully now that Sunjoe is offering an electric reel mower, Ryobi will bring their's to the states.


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## Lawndress (Jul 9, 2020)

I ended up getting the 40v Ryobi. I was actually able to mow the entire yard between the four batteries I now have and charging up as each died! The final straw was actually availability. Probably not the best decision, but I got home from my trip at 5 am, got some sleep, then went out to deal with the yard as soon as I woke up, and there was no way I could fix the lawn tractor in the time I had that afternoon.


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