Kohstar S520 Robot Lawn Mower Review

I can remember when simple self-propulsion on a lawn mower seemed like a big deal. Rather than having to move mowers forward with your own muscle power, the self-propelled option did all the work for you, and some of them at various speeds of your choosing. Heck, even riding mowers seemed like a new-age thing at one time.

But the S520 Robot Lawn Mower is a different beast altogether, and like cars that may someday drive themselves (though I’m not convinced that will happen en mass anytime soon), this robot is independent, safely designed, and intuitively controlled. It’s tough to give an overview of what amounts to a new age and type of mowing, but the important thing to know is that you won’t have to do much work if you purchase this item. And if that sounds good to you, read on, my friend. The only main concern about this mower is their does not appear to be any USA presence. The sales and support appear to be direct from China, which, could be an issue if support is needed down the road.

Key Features

  • Comes with four easily adjustable blades in case one gets damaged by debris
  • Large, heavy rear wheel keeps the mower well grounded on flat terrain, slopes, and hills
  • Auto recharge system means this robot will charge on its own without you having to lift a hand
  • Comes with a remote control and is waterproof
  • 19.7 x 19.7 x 31.5 inches
  • 88 pounds
  • 2-year warranty


When it’s ready to get mowing, this robot backs off from its charging station no different than you pulling your car out of the driveway. It’s pretty cool to watch, and once it’s operating on the yard,it kind of resembles the front half of a mini, mini car, almost as if it’s just the car’s hood in operation. Of course, a car doesn’t cut grass like this machine does, and does very well, I might add. It’s fun to watch this machine slice down thick grass and knotty weeds while taking a slug of your favorite beverage.

What’s truly notable about the S520 beyond its independent nature is how well it handles slopes and hills thanks to large, heavy rear wheels that keep it well grounded. Watching it tackle terrain that goes upward is fascinating, as it plods ahead as if nothing about the ground is different. It’s almost like cruise control on a car as the vehicle moves forward on roadways that slope upward or downward. The experience of watching a robot like this one cut grass is simultaneously mindless and highly functional, both robotic and smartly intentional. If you can’t tell by now, I’m highly impressed.

With a running time that ranges from two to three hours, the S520 is truly designed for large yards and can even handle grass in parks. It moves ahead at a nice, steady pace, around 35m/min, and has a cutting height that ranges from nearly an inch to roughly 2.4 inches.

Ease of Use

To say the Kohstar S520 is easy to use is nearly the understatement of 2018. Truly, it does all the work while you stand back and watch. And once you get over the initial thrill of a car-like robot cutting your lawn, you’ll likely forget all about it during the course of the mowing season and simply let it go to town on your lawn. The perimeter wire will prevent this machine from accidentally mowing your neighbor’s yard and beyond, and its various sensors will keep it mowing and operating on an as-needed basis.

The auto recharge system on the Kohstar S520 is also a great feature. When this robot is out of juice, it knows it and will go back to its docking station to “fuel up” its lithium-ion battery. It takes care of the entire charging process on its own, giving you one less thing to think about. The charging time is approximately three hours. Adjusting the included four blades on the mower is also easy, nothing more than turning a dial on the top of the machine.

Cut Quality & Options

Being a nifty robot, the Kohstar S520 offers cutting-edge features. For example, you can select what’s termed “sub-areas” for this mower to cut, which is a great option for larger yards that may have unseen nooks and crannies. It also can run in either random mode or in spiral model, the latter of which is just like it sounds: The mower runs in circles as it cuts. Either way, such cutting is way different than what the typical weekend mower might be used to, so the S520 does require a bit of faith on your part that it’ll get the job done as you watch it do its thing in a non-linear mowing fashion. Its cutting height ranges from 1 inch to nearly 2.5 inches.

One thing I’m not sure of is how this mower may run on damp or wet grass, or if it would even attempt to do so under such conditions. It’s waterproof but doesn’t run in the rain. The guess here is that it only mows when grass is dry. Please send me comments if you know otherwise!


Here some setup tips for the Kohstar S520:

  • The virtual wire should be laid at least 40 centimeters from the yard obstacle.
  • The distance between two virtual wires should be at least 2 meters.
  • Make sure the charging station is on flat terrain with no water, no magnetic interference, and no obstacle in front of it.

Other than that, you’re going to have to thoroughly check the manual to make sure you’re fully taking care of this high-tech machine.

Safety Features

When the S520 bumps into something, including the legs of a human, it senses the bump and simply backs up, preventing any unnecessary forward motion or injuries. The bump is slight since this machine doesn’t travel fast, so it’s unlikely to hurt sleeping pets or active children who might be running around on the yard. The “touch sensor” in back also automatically stops the machine when a human hand touches it, just in case it needs to be stopped. A similar “pressure sensor” on the top of the machine does the very same thing in the same manner. Just touch the top and the S520 will halt. Finally, the “lift sensor” goes into operation when the machine is lifted upward from the front. The blade will spin momentarily and then stop altogether.

Special Features

Forgive me if I’m a bit overwhelmed, but this robot has so many great features, it’s almost hard to know where to start. I mentioned the safety features of the touch, pressure, tilt, lift, and bump sensors above. The S520 can also sense rain, so it knows when to quit if the weather is bad. And it’s waterproof, so it should be okay when it’s connected back to its charger in the rain. The S520 also charges on its own and has an emergency stop switch. In many ways, it almost seems as if the Kohstar S520 is one big safety machine with ease-of-use features. It’s also got:

  • Password capability for operation
  • An electronic compass for navigation
  • A language option for inclusivity
  • Mowing schedule capability
  • Sub-area mowing capability for total coverage
  • Overload protection
  • Good mowing range for large-scale terrain

Cost Effectiveness

Once the S520 is paid for, it seems there are multiple ways it will ultimately save you cash and pay for itself in the end. Though it runs on lithium-ion batteries and must be charged, this machine could be considered environmentally friendly due to its long run times and the fact that it doesn’t produce nasty fumes into the air as it runs. It doesn’t require for you to pay for gas or oil but may at times have maintenance costs, especially after the two-year warranty is up. And think of the money you’ll save when you go on vacation and won’t need to hire the next-door neighbor to mow. The S520 will take care of everything while you’re gone. Overall, it seems there are multiple time- and money-saving ways robots like the S520 can offer.

Perhaps the best aspect of this mower is the time it will save YOU. That means more time to work on other projects you need to get done, or simply relaxing on the weekend instead of mowing under the hot summer sun.


7 Total Score
Nice machine but non USA origin concerns

  • Highly independent mower
  • Many high-tech, intuitive features
  • Basically no manpower required
  • Designed with safety in mind
  • 2-year warranty
  • May not thrive on long grass
  • May struggle with tough debris
  • May attract unwanted attention from kids
  • Could potentially get stolen
  • Maintenance costs potentially pricey
  • No USA website or presence
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Kohstar S520 Robot Lawn Mower Review
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