Xiaomi Mijia M40s: Record-Breaking 23,000 Pa, New Brushes, Lidar Sensor Built Into the Body

Hello to all readers of this project! This review will examine the Xiaomi Mijia M40s robot vacuum cleaner. It was the company's flagship model as of the end of July 2025. As befits a flagship model, the robot is equipped with advanced features. These include an object detection system, a retractable lidar system that allows cleaning under low furniture, a retractable side brush, a turbo brush with blades, and an all-in-one cleaning station. Overall, at first glance, everything looks very impressive considering the price. At the time of writing, it's very reasonable, ranging from $350 to $500. Below, I'll thoroughly test the Xiaomi Mijia M40s, highlight its pros and cons based on my test results, and then express my opinion on the robot. So, let's get started!

Equipment

The robot vacuum cleaner arrived in a branded box like this:

In addition to the robot and the station, the package includes two holders with cleaning cloths, a power adapter with a Chinese plug and a European adapter, and an instruction manual in Chinese. Not much.

Appearance

Now let's take a look at the Xiaomi Mijia M40s's design. Let's start with the robot vacuum cleaner itself. It's round and comes in white. A wall sensor is mounted on the right side.

In the center is a system of sensors for detecting objects, which is called S-Cross.

The height of the body with the lidar raised is approximately 103 mm. When the lidar is positioned inside the body, the robot's height does not exceed 88 mm, allowing it to pass under furniture up to 9 cm high.

The lidar itself, surprisingly, lacks a spring-loaded button to prevent it from getting stuck under furniture. Two mechanical control buttons are located next to it.

The dust container is located under the top cover. The filtration system is HEPA-only. The container holds 290 ml. The water tank is built into the robot, and water is automatically pumped into it via the station.

The robot has four anti-fall sensors on the bottom. It still lacks a carpet sensor, which has become a Xiaomi tradition.

There's one side brush. New design: quick-release, dual-beam. This prevents hair and fur from getting tangled. The brush extends into corners for thorough sweeping.

The central brush unit is floating. The turbo brush now has blades built into it, now on both sides. The side caps are removable for cleaning out tangled hair and fur. However, the end caps are not removable, which is not very convenient.

The familiar round holders with cleaning cloths are installed behind the turbo brush. One of the cloths extends to the edge to clean the floor right up to the baseboard. The cloths also automatically lift up when cleaning carpets, during dry cleaning, and when returning to the station. The holders themselves have been updated and are now spring-loaded.

Incidentally, as soon as I picked up the robot, it felt suspiciously light. My fears were confirmed. The robot weighs 3.8 kg, while even the M40 weighed 4.15 kg. In my opinion, light weight is not a good thing.

As for the station, the Xiaomi Mijia M40s self-cleans, automatically refills the robot's water tank, washes the wipes with hot water heated to 80 degrees, and dries the wipes with warm air at 45 degrees after cleaning.

I'd like to point out right away that this station doesn't connect to the water supply or sewer system, which is a serious drawback of this model, even compared to its predecessor, the M40. A separate built-in station is available for connection to utility lines. Incidentally, this version of the robot is also included in the review.

Conveniently, the robot's ramp and wipe-washing module are removable. Incidentally, it has also been updated with self-cleaning scrapers for the station's bottom.

A trash bag is located under a cover above the robot's parking area. There's no detergent reservoir, although space for one is provided. This means this station isn't capable of mixing detergent at all, whereas the M40 at least had this capability via a module for connecting to utility lines.

The water tanks are located under the top lid. They have a larger capacity, holding 4 liters each. The clean water tank has a disinfection module, which is a plus.

We see that the new M40s has received several important design updates, but some components have also become worse. All the pros and cons we've identified will be discussed in the final review. Let's move on!

Technical specifications

The main characteristics of the Xiaomi Mijia M40s, as stated by the manufacturer:

Robot vacuum cleaner:

• Li-Ion battery 5200 mAh.
• Suction power up to 23,000 Pa.
• Cleaning area> 200 sq.m.
• Dust collector: 290 ml.
• Water tank: ≈ 80 ml.
• Obstacle clearance up to 20 mm.
• Dimensions: 350*103/88 mm.

Station:

• Clean water tank: 4 l.
• Dirty water tank: 4 l.
• Bag in the station: 2.5 l.
• Dimensions (W*D*H): 360*470*572 mm.

The claimed suction power has been increased compared to previously released models, and the body has been lowered. Other specifications haven't changed significantly.

Functional capabilities

Regarding controls, the robot vacuum cleaner is designed for the Chinese market and connects to Mi Home via the China region. There are no regional locks, so don't worry. At the time of writing, the interface is in English, which isn't ideal. The app is responsive and easy to use.

The main functions of the Xiaomi Mijia M40 are displayed on the screen:

• Self-cleaning dust collector.
• Washing napkins at the station with hot water (80°C).
• Drying napkins with warm air (45°C).
• Lidar entering the body.
• Side brush extension in corners.
• Moving the napkin to the baseboard.
• Identifying objects on the floor.
• Saving multiple cleaning maps in memory.
• Automatic zoning of premises into rooms.
• Selecting areas and rooms for cleaning.
• Virtual walls and no-go zones (and for wet cleaning mode).
• Suction power adjustment.
• Setting the frequency of washing napkins.
• Cleaning log.
• Setting up cleaning according to a schedule.
• Automatic power increase on carpet.
• Carpet cleaning in wet cleaning mode.
• Lifting napkins when driving onto carpets.

I'd like to point out that we've added a "Thorough" cleaning mode, which makes the robot clean in a tighter zigzag pattern. We've also added flexible cleaning settings via a quick start scenario, allowing you to set up to five customizable cleanings with individual parameters for each scenario. We've also added a 3D room map, flooring type selection with adjustable laying direction, and a setting for rinsing the cleaning pads at the station after a set time. We've also added options for the robot's behavior when cleaning carpets. Overall, we've seen a slight update in functionality.

What I didn't like was the lack of the ability to manually set zones where the robot vacuum cleaner should lower the lidar, as is the case with similar products. I'll show you why this is a disadvantage in my tests.

Testing

A detailed video review of the Xiaomi Mijia M40s, including all tests, has already been prepared and published on the channel:

Navigation

And finally, let's move on to the tests. First, we'll test the Xiaomi Mijia M40s' navigation in a room with obstacles. The robot vacuum first moves around the perimeter of the room, then cleans the entire accessible area in a serpentine pattern. It moved over the dryer's legs. It also swept around the box and the chrome legs, then returned to the station. No unusual maneuvers were detected, so the test was successful.

Speaking of navigation within the house, the robot vacuum cleans room by room, following the perimeter, then in a serpentine pattern. After each room, as I've determined, it returns to the station and washes the wipes, then resumes cleaning from where it left off. There are no uncleaned areas left; this model has excellent navigation!

Passing under low furniture

The minimum driving height of the Xiaomi Mijia M40s was also tested. Since it's impossible to manually set the zones where the lidar should be lowered, the robot decides when to do so. And from my observations, it didn't even manage to enter a 9 cm gap on the first try. To be precise, it only decided to lower the lidar and enter the gap on the third try. It's good that it succeeded, but bad that it didn't do so immediately. It's unclear how many times it would take to enter such a gap in a real-life situation, or even if it would.

Autonomy

I tested the battery life when running the robot at maximum power with wet cleaning enabled. It lasted 109 minutes, cleaning 76 square meters of usable space. In reality, that's almost enough for two full cleanings of a 70 square meter two-bedroom apartment. It also features a resume cleaning mode after recharging at the base, so this model is capable of cleaning larger areas.

Identifying objects on the floor

As for the object avoidance system, I can say it's nonexistent, absolutely nonexistent. Judge the results for yourself. In good lighting, the robot avoided only one of six household objects—a large toy, which robots without object avoidance systems avoid as well. Of the three socks, it only avoided one, merely brushing the second and chewing the third. It brushed against all four wires, tangling three of them. It also ran over all six simulated pet surprises, and almost every one of the traps blocked the brush, requiring manual release.

In the dark, the situation is no better: out of 6 household objects, he only drove around a toy, moved all 3 socks and chewed one of them, chewed 2 of 4 wires and simply moved 2, and also ran into all 6 traps in the so-called minefield.

In general, don't expect this model to handle objects neatly.

Suction power

At least the suction power is good. In Quiet mode, the Xiaomi Mijia M40 was able to partially clean a 2 mm gap. In Standard mode, it did better at 2 mm. In Boost mode, the robot partially cleaned 4 mm, and in Turbo mode, it did a better job at 4 mm, as well as partially cleaning 6, 8, and 10 mm.

That is, the power is actually high, but compared to the M40, which claims to have almost half as much – 12,000 Pa, its predecessor managed to clean out debris even from a 14 mm gap and cope better with the task in the first three modes.

Dry cleaning

The quality of debris collection on laminate floors is good, regardless of the structure. Moreover, thanks to the retractable side brush, this robot even managed to clean debris in the corners. However, only on the fourth attempt. You can see that the sweeping algorithm isn't very consistent, requiring several passes through the corners to completely clean them. This issue occurs with both internal and external corners.

And here's the condition of the cleaning module. The central brush had picked up a bit of hair, but simply didn't have time to cut through it. But the side brush is completely clean, which is great!

Anti-tangle Hair Protection

I also tested the turbo brush to see how it handles cutting through tangled hair. Even after this challenging test, the turbo brush is noticeably cleaner than its competitors.

I even tested the turbo brush's effectiveness after a week of cleaning in a residential setting. The apartment is home to two girls and a perpetually shedding corgi. The brush is completely clean, and it really does an effective job of cutting hair and fur!

Carpet cleaning

Regarding carpet cleaning, the robot thoroughly cleans low-pile carpets. However, on medium-pile carpets, the object detection system can recognize the pile as an obstacle, causing the robot to avoid certain areas. The object detection system can't be turned off. It would be better if it weren't there! The carpets it passed through cleaned, but in any case, the test couldn't be counted. Incidentally, the same issue was observed with both the Mijia M40 and M30s. So it's really strange that it hasn't been fixed in the new product!

Wet cleaning and carpets

As for wet cleaning in the presence of carpets, there's always a caveat. Since the robot lacks a carpet detection sensor, it can't automatically detect carpeted areas. You need to manually set them on the map. After that, you'll be prompted to choose one of two interaction modes: avoiding carpets or driving over them with the cleaning pads raised.

Self-cleaning

Immediately after the "dirty tests," I checked the robot vacuum's self-cleaning performance. After the self-cleaning, the dust bin was completely empty, so this robot's self-cleaning is well-implemented! The result was excellent. However, the HEPA filter was clogged with debris; a mesh screen would have been a good idea.

Wiping off dirt

This robot vacuum does a good job of removing dirt. It leaves no streaks or marks, and it can even thoroughly clean along walls and furniture. However, in my case, for some reason, the cloth didn't clean the floor right up to the wall. The robot maintains a short distance, which can result in a blind spot of up to 5 mm.

Removing difficult stains

When it comes to cleaning tough stains, the Xiaomi Mijia M40s was able to remove most stains in just 10 passes. This is a standard result for similar robotic vacuum cleaners.

Washing quality of napkins

Now, I'd like to talk about the effectiveness of the station itself. Let's start with the quality of the wipes' washing. Even after extensive testing, the wipes look significantly better after washing with the station.

In a domestic setting, after washing the floor, the wipes are thoroughly rinsed at the station. They appear clean.

The station itself is very easy to clean. It does this automatically with its scrapers, but occasional outside intervention is a good idea. There's a self-cleaning function activated by a button on the station, but it's best to periodically remove the tray and drain and rinse it in the sink.

Obstacle clearance

The robot vacuum easily navigates 2 cm high thresholds, lifting up the cleaning cloths as it goes. That's a plus!

Driving on black surfaces

It's also not afraid of black surfaces, easily driving on completely black carpet. This is another advantage of the robot!

Noise level

As for the noise level, it ranges from 56 to 69 dB. This is lower than most similar products, especially considering its high suction power! The station's noise level during self-cleaning is around 74 dB. This is already a standard result.

Personal opinion

The Xiaomi Mijia M40s robot vacuum cleaner has been thoroughly reviewed and tested. According to our rating system, it scored 189 points, giving way to his predecessor M40, which scored 192 points. It's logical; I'll justify my score when summing up the results.

Overall rating of tested robot vacuum cleaners: https://robovac.washerhouse.com/en/rejtingi/robovac-obshhij-rejting-robotov-pylesosov-robo.html.

I'll highlight the pros and cons I discovered, and then express my own opinion about it. I liked the following:

1. The most important thing is the optimal price, considering its capabilities. At around $400, only its sibling, the M40, can compete with it.
2. The lidar slides into the body, allowing the robot vacuum cleaner to clean in gaps as small as 9 cm.
3. The updated side brush does not tangle fur and hair.
   The turbo brush self-cleans with built-in blades and doesn't get tangled with hair or fur. There's no need to clean it manually.
4. The robot vacuum cleaner is able to sweep out debris from corners thanks, again, to the retractable side brush mechanism.
5. High suction power. While not as powerful as advertised, the robot nevertheless delivered decent results.
6. The cloth extends to the edge to wash the floor along the walls and furniture.
7. The water heating temperature for washing napkins at the station has been increased.
8. Overall, having an all-in-one station for the money is a big plus.
9. Convenient maintenance of the robot and station, thanks in part to scrapers on the bottom and brushes with protection against hair tangling.
10. High-quality dry and wet cleaning on hard surfaces and low-pile carpets.
11. The app allows you to flexibly configure cleaning parameters.
12. Good cross-country ability.
13. Spacious tanks at the station.
14. The robot vacuum cleaner is not afraid of black floor coverings.
15. Low noise level of the robot itself.
16. A version with an ultra-thin built-in station is available for sale.

As for the disadvantages, there are also quite a few of them:

1. The first and most important thing for me is that this version of the station doesn't connect to the sewer or water supply at all. It would have been great if there had been a choice between regular tanks and a module within a single station.
2. Let's move on. The robot vacuum cleaner is designed for the Chinese market. It doesn't speak Russian, and the app interface isn't fully translated. Furthermore, there's no full service or warranty support from the manufacturers. Yes, the app can be localized and even custom voice-overs added later, but that's an additional hassle, especially if you have an iPhone.
3. The system for identifying objects doesn't work at all and it would be better if it didn't exist, it does more harm.
4. There are issues cleaning medium-pile carpets. The robot avoids certain areas of the carpet, detecting the pile as an obstacle, precisely because of the sensor system on the bumper.
5. There is no carpet sensor, which is why you need to manually set carpet zones on the map.
6. There is no function to automatically mix detergent with water.
7. The assembly has become cheaper, even compared to the M. The robot has somehow become lighter, they removed the button from the lidar cover, I’m not sure that the brush with knives has become better than the previous one, and the power has somehow disappeared, compared to the M40.
8. And finally, you can't manually set the zones where the lidar should be lowered. You have to rely on the robot to figure it out and, after a few tries, begin lowering it.

So, what's the bottom line? I'm not saying it's a bad robot vacuum. For the price, it's quite good, considering its features, the docking station, and the high-quality cleaning performance. However, the removal of the utility connection from the regular docking station and the fact that some features are poorly implemented have left a mixed impression. It turns out that the Mijia M40s isn't a true flagship, but simply an alternative to the M40 for those who want the lidar sensor and other upgrades.

If you're on a budget, the robot is definitely recommended, especially if you don't have medium-pile carpets. But all the comments are like, "The M40s is just as good." Dreame X50 Ultra Complete, now they simply don't make any sense. There is a difference, and it's colossal, but whether it's worth saving or overpaying is up to you to decide.

On that note, I'd like to end this review. If you have any questions, please ask them in the comments. Happy shopping, everyone. Bye!