Mowing my yard is one chore I never look forward to. Well, at least not as I get older. I used to love mowing the grass for the workout, but now it does nothing but trigger my allergies.
I’ve experimented with robot lawnmowers in the past. I’ve paid $175 a month — even during the winter, when they weren’t in use — to rent a couple of Husqvarna mowers from a landscaping company. Eventually, I realized it wasn’t a wise investment, so I canceled the contract. Later on, I tested the EcoFlow Blade for a while, but its wheels loved to dig holes in my yard with each and every turn, so eventually I stopped using it.
For the last month, I’ve been testing the Sunseeker S4, a robot lawnmower that leverages AI and LiDAR for mapping and navigation. I don’t want to spoil the review, but I’m smitten.
Sunseeker S4 review: Price and availability
The Sunseeker S4 is currently available directly from Sunseeker with a regular price of $1,799 but a sale price of $1,299, but Amazon has it on sale right now for just $984. That includes the robot lawnmower, a docking station, extra blades, and a cleaning brush for the LiDAR sensor.
If you’re reading this and the S4 has returned to its normal price, I’d wait for a sale.
Sunseeker S4 review: Design
Image 1 of 6
Sunseeker S4 specs
Weight: 26 pounds
Dimensions: 25.12 x 16.61 x 10.79 inches
Waterproof rating: IPX6
Connectivity: Wi-Fi, Bluetooth
Cutting width: 7 inches
Cutting height: 1.6 to 3.2 inches
Max slope: 42%, 22°
Noise level: 60 dB
Battery: 20 V Lithium 4 Ah
Max mowing area: 0.25 acre
The S4 doesn’t break the mold when it comes to the robot lawnmower’s overall design. It’s compact, measuring 25.12 x 16.61 x 10.79 inches, and weighs 26 pounds. In the event the robot gets stuck somewhere and you need to lift it, there’s a handle built into the rear of the housing that makes it a breeze to pick up.
On the front of the S4 is a monocular camera with a 360-degree LiDAR sensor on top. It’s tucked into a bumper that slightly moves in when the lawnmower presses against a hard object, The sensor is easy to spot due to its black bubble-like housing.
Behind the LiDAR bubble is a flip-up cover that hides an LCD display and a few buttons you can use to interact with the S4 — although I rarely had a need to do so — and a manual dial you use to adjust the cutting height, which ranges from 1.6 to 3.2 inches. There’s a giant red STOP button that you can press to immediately stop the S4 in case of an emergency.
Underneath the stop button is the handle I previously mentioned. The S4 is rear-wheel driven with two trolley wheels that spin and move wherever the two rear wheels push the robot. Sunseeker’s specs put the max gradient at 22 degrees — a stat that didn’t apply to my mostly flat backyard. However, there’s a slight slope to my front yard (I’ve never measured it), but the S4 didn’t have any issues with slipping, even if the grass was wet.
When you flip the S4 over, you’ll see six blades attached to a disc. It always amazes me when I test a robot lawnmower how small the blades are; they often look like razor blades you’d find in a box cutter.
Sunseeker S4 review: Installation and mapping
Setting up the S4 was a breeze. You’ll first need to decide where you want to — and can — install the charging station. It measures 30 x 19 x 14.5 inches and can be placed at the edge of your yard, or even outside of it if you’d rather. You’ll need a weatherproof electrical outlet nearby.
I already had a section of my yard that’d been killed by previous robot lawnmower docks, so it was an easy choice for me. I swapped out the old broken station and replaced it with the Sunseeker S4 in about 10 minutes. After sliding the S4 into the charging station, I created an account in the Sunseeker app, connected the S4 to my account and waited for the battery to fully charge.
The app walked me through the initial mapping of my yard, which required me to drive the S4 to a starting point along the edge of my grass. At that point, I could either continue to use my phone as a Bluetooth remote control and manually map my yard, or I could let the S4 automatically roam around the edge and create a map on its own. I stood by, ready to take over if needed, but the S4 slowly and judiciously creeped along the edge of my grass.
The S4 is the first robot lawnmower I’ve used that maps on its own, and I was impressed. There were a few areas I had to go back and manually drive the S4 over, adding to the existing map, but it was a much easier and streamlined process than I’d experienced with the EcoFlow Blade.
After mapping my backyard, I created a second zone, consisting of my front yard and let the S4 work its magic with mapping. There are a couple of trees in that yard, along with more corners and angled sections — unlike my backyard that has three flat edges. The S4 needed a little more help with correcting the front yard’s map, but overall the process was simple.
So simple, in fact, I deleted both maps in the app and went through the process multiple times with similar results. You can save maps in the Sunseeker app and easily switch between them, which is also a nice touch.
My favorite part of mapping my yard, however, wasn’t how easy it was, but instead it was the 3D map the LiDAR sensor created that I could view in the app.
It’s one thing to read that a device has LiDAR and assume it’ll help with object identification, navigation and mapping — but it’s another to actually see what the S4 sees, down to the batting cage in the back corner of my yard along with the power and cable lines that run above my yard.
As far as object detection and avoidance goes, the S4 routinely routed itself around objects as big as my English Bulldog who walks in front of it daily, or as small as a Wiffle ball my kids leave in the yard. I didn’t expect it to see the latter at all and run it over instead, but once it gets within a few inches, it stops, slightly turns and goes around it.
Sunseeker S4 review: Performance
With two zones created, I used the Sunseeker app to create a path between them. I then set a schedule for Zone 1, the backyard, to be mowed Monday-Friday between 9 a.m. and 5 p.m. There’s a gate between my yards, so I couldn’t set a schedule for Zone 2 as I have to manually open and close the gate when the robot needs to get through.
According to the Sunseeker app, Zone 1 is 3,184.96 square feet and Zone 2 is 2,690 square feet, for a total of 5,874.96 square feet between the two.
The initial pass over my backyard with grass — which was longer than I’d like to admit — required a couple of trips to the charging station. The S4 ran for around 90 minutes each time, and then took a couple of hours to charge before heading back out to complete the task.
The same can be said about mowing the front yard, which I asked it to do the following day. That process was tedious, only because I had to monitor the battery status in the app to let the S4 into the backyard so it could charge, and then let it back out once the battery was full. In total, it was two trips back and forth.
However, after that initial cut, the S4’s cut time has dropped significantly. The backyard does require a return trip to charge for a little over an hour, then it heads back out for 20 minutes to finish the job. In total, it takes just under 2 hours of cutting time to mow the backyard — or just over 3 hours if you include charging time.
If I’m paying attention, I can catch it right after it finishes the backyard and manually redirect it to the front yard. From there, it tackles the rest of the lawn and returns to the dock on its own, completely finished in roughly an hour and forty-five minutes.
As for how good of a job it does at cutting grass, for the first few sessions it’d leave little rows of grass between each pass with the default cutting direction setting. However, after switching the cutting direction to traceless, which means each time the S4 cuts it changes direction, those missed rows have disappeared. If you’d prefer to have patterns cut in your yard, you can set the S4 to create items like a heart, a trophy, a star, or a soccer ball. It can also cut a pattern to represent numbers.
My lone complaint about the cutting performance of the S4 can be said about any of the robot lawnmowers I’ve owned — none of them can cut the edge of the yard. For the S4, it has a cutting width of 7 inches, but there’s 4.3 inches between the edge of the lawnmower’s housing and the blades. So, no matter how close you get the map to the edge of your grass, there’s always going to be a small section of grass it just can’t cut.
It’s a fair trade, I guess. Instead of having to bribe my son to mow the yard maybe once every two weeks, my yards are mowed multiple times a week.
Sunseeker S4 review: Storage & maintenance
The S4’s charging station serves as the main storage area for the robot when not in use. Along with charging it, there’s an overhang to protect the top of the S4, complete with a brush to keep the LiDAR bubble clean. If you want more protection, Sunseeker sells a Sunproof Garage that extends the protection to the entire lawnmower.
During the winter months — and for that matter if you’re expecting a lot of rain — I’d recommend removing the S4 from the dock and moving it indoors. During my testing, I had a rainstorm come through that dumped two inches of rain on us in an hour. It took me a couple of days to notice the S4 hadn’t run on its set schedule, and upon further inspection I realized it wasn’t even turning on.
I turned it upside down, removed the battery and let it dry out for a day, after which it came back to life. I have no idea how high the water got in my yard, but I do know there was standing water most of the night.
It’s a good reminder that even though the S4 has an IPX6 waterproof rating, it’s still susceptible to the elements.
As for routine maintenance on the S4, the Sunseeker app has a device maintenance menu that tracks when you should replace the blades (after 120 hours of use) and when you should wash the cutting disc (after 60 hours of use).
Otherwise, keeping the front camera and the LiDAR bubble clean are the only things you need to worry about.
Sunseeker S4 review: Verdict
This was my first time using a Sunseeker robot lawnmower, and it did not disappoint. My yard hasn’t consistently looked this good in years. The Sunseeker S4 was easy to set up, forgoing the need to install a dedicated GPS antenna like the EcoFlow Blade, or bury a guide wire like previous Husqvarna mowers I’ve used.
Battery life is good enough for its 0.25-acre limit, and after fine-tuning the settings you’ll get a clean cut every time.
Well, except for the edges. Make sure to keep a trimmer handy.