Xiaomi Robot Vacuum S40 Pro Review

Design and features

• No-frills charging dock
• Swing-out arm and mop
• Works with the Mi Home app

Pretty much every vacuum cleaner comes with a full self-empty, self-clean docking station. Even the Xiaomi Robot Vacuum X20 Pro came with one, and that’s not available for just over £360. The Xiaomi Robot Vacuum S40 Pro is different, as it’s more of a throwback to the original days when robot vacuum cleaners came with a simple charging dock only.

There are clear downsides to doing everything manually, but the benefit of a simple dock like this is that it’s easier to place and hide, such as under a sofa.

The closest robot to the Xiaomi Robot Vacuum S40 Pro that I’ve reviewed recently is the Roborock Q5 Pro, but just over a year later, you can see how far robot vacuum technology has moved on.

Not only is the S40 Pro cheaper than the Q5 Pro was at launch, but it’s also quite different. Flip the S40 Pro over and there are dual microfibre mopping pads, which spin to agitate and remove dirt; the Q5 Pro had a basic mopping pad that it dragged on the floor.

One of Xiaomi’s mopping pads also swings out to clean the edges of rooms, which is an impressive feature at this price.

To use the mop, the S40 Pro needs its 310ml water tank filled manually, which should then be enough to clean a typical floor in an average home. The main downside is that without a self-cleaning dock, you’ll need to remove the mop pads and wash them yourself after use.

When carpets are encountered, the S40 Pro can lift its mop pads by 10mm, which lets it navigate over most short-pile carpet. There’s no option to automatically have the mop pads removed for vacuuming only, so if you’ve got mixed flooring a higher-end robot, might make more sense.

Otherwise, the underside of the S40 Pro is pretty much what you’d expect: a single side brush, which is mounted on a mechanical arm for edge and corner cleaning.

Xiaomi says that the main brush is designed to be anti-tangle, with bristles designed to keep hair straight and directed towards the main suction path.

Dirt goes into a 430ml bin, which is actually a little larger than you get on most modern cleaners. That’s because this bin has to be removed and emptied by hand after each clean. And, you should wash the filter regularly, too.

Although the robot has shortcut buttons on top to start and pause a clean, and to return it to the dock, you’ll get more out of it if you use the Mi Home app. Once the robot’s connected to the app, it needs to perform a short mapping run.

This is quick, thanks to the LiDAR dome on top, and the map shows up soon after. As with most robots, the S40 Pro suggests a room layout. In my case, the app added too many rooms, but it was easy to merge the wrong ones and get the layout that I wanted.

I could also add furniture (useful as a quick-select zone), and set no-go zones, which can be useful if the robot gets stuck in one area or you have somewhere you really don’t want the Xiaomi Robot Vacuum S40 Pro to clean.

Cleaning options include cleaning the entire home, a room (or rooms) of your choice, or a custom area that you draw on the app.

For cleaning, there are all of the options that you’d expect: vacuuming, vacuuming & mopping, vacuuming before mopping, and mopping only. There are then four levels of suction to choose from and three levels of water flow.

There’s not much in the way of advanced features, with the option to toggle the mop and side brush swings independently, a child lock to turn off the buttons on the robot, and carpet recognition, which boosts power when carpet is detected.

Performance

• Decent vacuuming
• Mopping works well on lighter stains
• Navigation a bit hit and miss

I put the Xiaomi Robot Vacuum S40 Pro to work cleaning up my regular spills. I started with the carpet test, adding a teaspoon of flour to the carpet. With 15,000Pa rated suction power, this robot doesn’t match flagship robots, but that’s still a lot of power; in fact, it’s more than twice the suction power of the Xiaomi Robot Vacuum S20 Pro.

Overall, the performance in this test was very good. There are some traces of dust left behind, and a couple of concentrated clumps, but overall collection was excellent after two passes.

I added the same type of dirt to the hard floor, but in vacuum only mode, only most of this mess was collected, with the flour spread around. Tackling the rest with the mop helped.

Similarly, the edge test left quite a bit of mess behind. While the side brush teased some mess out from the kitchen plinth, a lot of the dust was swirled around. For lighter messes, the Xiaomi Robot Vacuum S40 Pro will do well, but edge vacuuming could be better.

Putting strands of human hair on the floor, I found that a lot of these ended up wrapped around the brush bar – the anti-tangle isn’t as good here as I’ve seen on other robots.

I then moved on to the mopping test. I didn’t hold out much hope, as budget robots aren’t usually very good on this task, but the Xiaomi Robot Vacuum S40 Pro impressed. With my dried-on coffee stains, two passes largely removed everything with just a faint stain left behind.

My red wine stain fared better, with the Xiaomi Robot Vacuum S40 Pro able to completely remove that mess.

Likewise, the mud stain was removed: first, the robot vacuumed up the loose particles, and then the mop removed the mud.

My toughest mopping test is the dried-on ketchup mess. Here, the Xiaomi Robot Vacuum S40 Pro struggled. There’s some reduction in the stain after two passes, but the robot couldn’t do much to shift this mess.

Navigation is generally good. There are cameras to avoid a lot of obstacles, but I did find that the Xiaomi Robot Vacuum S40 Pro had a tendency to make its way towards the sledge-leg desks in the Trusted Reviews Home Technology Lab, and clamber noisily over them. I didn’t notice this robot getting stuck anywhere.

On its highest power setting, the Xiaomi Robot Vacuum S40 Pro came in at 60.4dB, which sits about average for robot vacuum cleaners: loud enough to hear, but quiet enough that you can be in the same room while it’s cleaning up.

Battery life isn’t quoted, although Xiaomi does say that the robot can clean up to 180m² on a single charge, while mopping. What I can say is that the robot managed a couple of vacuuming passes of the lab on a charge and had enough power left to tackle the areas for hard floor testing.

Should you buy it?