Ecovacs Deebot N79S

Cheap and Cheerful and gets the job done.

Edit 07-Aug-2023: 19 months after buying this robot and using it every few days, it is dead. Mechanical failure means that one of the wheels is no longer connected to the motor that drives it, so the robot basically goes round in small circles.

If you're looking for a smart appliance with all the bells and whistles then this is not it, but it doesn't pretend to be it anyway. This is an entry-level vacuum cleaner robot that fumbles around more or less randomly, cleaning up whatever is in its path.

The reason I bought this is because I wanted to see how well the technology coped with a small home on one floor that really is quite cluttered to be honest. If it doesn't cope well, then no great loss. If it does, then I know I can invest a bit more when this one comes to the end of its life.

The robot comes with an infra-red remote control allowing you to access its basic features: auto clean, room clean, edge clean, spot clean and return to dock. It also allows you to set up the Wi-Fi link and to program the timer to get it to start cleaning automatically at a set time every day. Then there's an app (there are both Android and iPhone versions) that provides a bit more control. Finally, there's an Amazon Alexa skill allowing you to give basic commands by voice. Presumably, there's an equivalent for the Google smart home ecosystem as well, I honestly don't know. I'm an Alexa user myself.

What I think we can take home from a few days of using this robot is that it's a good piece of hardware for the price that is let down by some poor software. Atrociously poor software, to be honest. The vacuum cleaner part of it works really surprisingly well for something in this price range (nominal price is around £200 but it can be found for as little as £150 or even less if you look around − as of 1/1/2022 Amazon UK are selling it for £129 for the next 8 days). The robot is fairly quiet despite suction power that is really not bad. The dust receptacle is large enough to do the entire flat with capacity to spare and the various consumables (filter, beater, brushes etc.) are easy enough to replace. Clearly it's going to be a lot slower than a traditional vacuum cleaner because it's less powerful and smaller, but does that matter? You just start it and let it get on with the job while you're doing something else with your time. You don't even need to worry about the battery going flat because the robot will sense this condition and simply return to its charging dock.


Firstly, let me stress that this is not one of those fancy robots with lasers that map out the environment and show you a floor plan on your phone or tablet on which you can define zones, no-go areas etc. This thing is dumb and nearly blind. If you're looking for the really smart kind of robot then you're going to be disappointed with this model. Then again, what do you expect for less than £200?

There are four cleaning modes with this robot: auto, single room, edge and spot. All can be engaged either using the remote control or the mobile app.

Auto clean mode

This is the simplest of the four modes. The robot really does mill around randomly, sucking up dust in its path. It'll set off in a random direction until its optical sensors detect an obstacle close ahead, until the fall detectors on the underside tell it that it's about to walk off an edge (e.g. staircase) or until it bumps into something low down that was below the optical sensors' line of sight. It then sets off from that point in another random direction until it encounters another obstacle. If it bumps into obstacles in quick succession, i.e. if it gets itself into a very confined space, then it attempts to edge around the obstacles until it reaches an opening through which it can make good its escape. The mobile app lets you switch between "standard" and "max" suction power in auto clean mode.

Single room clean mode

This is similar to auto mode except that the robot limits itself to a single room. In auto mode, if setting off in a random direction makes it wander out of the room into another then so be it, it'll just clean there too. Not in single room mode. However, for it to work in single room mode, the room needs to be sealed anyway so the robot can't escape. I'm not really sure how this differs from auto mode (cough, splutter, marketing ploy, cough cough). I wouldn't be surprised if the firmware does exactly the same thing in both modes.

Again, just like in auto clean mode, you can switch between "standard" and "max" suction power.

Edge clean mode

This one does actually differ from the other two. I find it useful in the kitchen, where crumbs, bits of onion skin etc. get dropped near the work surfaces, which are on the periphery of the kitchen. The robot makes its way to the edge of the room and then feels its way around the edge anticlockwise while operating at full suction. There are rotating brushes at the front of the robot, a bit like the antennae on an insect, that reach to the very edge of the floor and feed particles into the path of the main beater under the robot's belly. Part of my morning routine now includes letting the robot loose in the kitchen after I've had breakfast so it can clean up the mess of crumbs I inevitably leave.

If you want the robot to concentrate on the edge of a single room then that room clearly needs to have its exits blocked, or the robot will happily travel around the periphery of your entire living space.

Spot clean mode

Again, this differs from the other modes. You basically plonk (or drive) the robot right into the middle of a patch that has a lot of dirt to clean up and then fire up "spot" clean mode. For the next 3 minutes or so, the robot will clean at maximum suction power, starting by spinning on itself and then moving in concentric circles with increasing radii.

Going home

Remember, this robot isn't as smart as some. It doesn't actually have a clue where it is in relation to the charging dock or what the topology is of your rooms, so whenever it needs to go home for a power top-up, it has to "look" for the dock. This can actually be quite hilarious watching the thing wander off in the complete opposite direction to where it should be going, not to be seen again for the next 5 minutes while it's looking for the dock under the bed or in the bathroom. There is some kind of optical guidance system at play as far as I can tell because as soon as the robot has the dock in its line of sight, it homes in on it very accurately. Until then, it's really just dumb luck.

The dock must be against the wall or skirting board, placed nice and perpendicular to the wall and with sufficient clearance either side. The manual recommends 1 metre either side but it has a good deal less than that here, closer to 40cm. It had even less than that where I initially placed it but the robot did get confused and had a hard time aiming for it, kind of like it was trying to park after a few too many...


As with any vacuum cleaner, whether automatic or manual, you need to make sure that you take any objects that can potentially damage the robot off the floor.

Things like wires, pieces of string, carrier bags, frilly bits on the edge of rugs (you can fold those under the edge of the rug) and the like could easily get tangled up with the robot's moving parts. Don't leave them hanging around on the floor. You would see them and move them while you're working with a traditional vacuum cleaner but you don't necessarily think of them when using an autonomous appliance like this.

Don't use this on deep pile carpets either. The pile will just wrap around the beater.

This is not one of those robots that also mops. It does not like water. If you have pets, lift their food/water bowls off the floor so that the robot doesn't bump into them and slosh water and/or wet food over itself.

Battery life

This robot is powered by a replaceable Li-ion battery that is charged either by plugging the supplied charger's barrel connector directly into the robot itself or by plugging the charger into the charging dock that the robot "drives" into when it's finished working.

Battery life will depend on many factors including the type of surface you're cleaning, the number of obstacles to navigate around and the suction power. The manual doesn't mention battery life, although the Amazon page I linked to above gives 90-120 minutes. The ballpark range you can expect is more likely to be 60 to 90 minutes after adjusting for the fact that the manufacturer's figures are more than likely theoretical figures in perfect conditions. Again, this doesn't really matter a whole lot because the robot will carry on doing its thing until it thinks the battery needs recharging, at which point it'll make its way back to the charging dock anyway (via the bathroom and under the bed).

Update 3/1/22: I let the robot start at the preprogrammed time today and continue until it sensed a low battery condition and returned to its dock. It docked 86 minutes after starting its cycle.

Controlling the robot

One positive feature of this robot's design is that the app, the dock and the remote control all add features that don't actually prevent you from using the robot if you don't have them. If all you have is the robot and the charger, then you can plug the charger directly into the robot and, when you need to use the robot, you just unplug it, press the "Auto" button on it and let it do its thing. When you're done with it, you press the "Auto" button again to stop it, carry it back to the charger and plug it back in again. As long as the robot is charging, it's not going to try and run away unless you tell it to move.

If you have the charging dock then you plug the charger into that. Just press the "Auto" button on the robot and it'll leave the dock, start vacuuming and return to the dock when it needs charging. Or you can pick it up and put it in the dock yourself.

Remote control

One of the first things you'll do with the remote control is use it to connect the robot to your Wi-Fi router. More on that in the next section dedicated to the mobile app, but suffice it to say that this is where the problems start.

The remote also has buttons to drive the robot manually, to start all of the four cleaning modes, to pause or resume cleaning and to tell the robot to return to the charging dock. It also features an LCD screen showing the time of day and the current status of the robot. Finally, it has buttons to set the current time of day on the remote, to program an automatic starting time and to cancel the programming. If an automatic start time is programmed, the robot starts cleaning in auto clean mode until the battery gets low and then returns to the dock. This sounds practical, but in fact it's where more problems start.

No programming of any kind is stored in the robot. It's all stored in the remote and when the programmed time is reached, the remote transmits the "auto clean" command via its IR transmitter. This means that the remote must always be placed pointing at the robot's charging dock. If the remote is in a different room or just pointing in the wrong direction, the robot won't see the "auto clean" command and, predictably, won't start cleaning. Bummer.

Assuming the remote is pointing correctly at the robot, remember that it must be set to the correct time of day. If it isn't, then the robot will start cleaning when the remote thinks it's the time that you programmed, not necessarily when it actually is that time.

Mobile app

Where to begin...

The robot only works on 2.4GHz Wi-Fi, which is fair enough. It doesn't need to transmit/receive large amounts of data so it doesn't need the speed advantages of 5GHz Wi-Fi. However, this is where the first (huge!) bug in the app rears its ugly head. The process for adding the robot to your network involves pressing a button on the remote for 3 seconds and following directions on the screen in your mobile app. If you have a Wi-Fi router that operates on both the 2.4GHz band and the 5GHz band (nearly all do these days) and if your phone/tablet is connected on the 5GHz band (like most do these days), then the app considers that your router is 5GHz only, claims that the robot can't connect to it and doesn't allow you to proceed any further.

Why not just allow the robot to attempt to connect? Duh!

There is a solution to this conundrum. Most Wi-Fi routers let you manage the 2.4GHz and 5GHz networks independently, so the idea is to deactivate the 5GHz network on the router while setting the robot up (your phone or tablet will still connect to the 2.4GHz network to complete the setup), then to reactivate it. Once this is done, your robot is linked to the account you set up with Ecovacs.

The robot goes into low power mode once it has finished charging and hasn't been used for a while. Great for saving power but not so great for the app. Once this happens, the app doesn't "see" the robot any more and it remains unreachable for about 30 seconds. If you try and drive the robot using the app while it's in this status, you get error messages saying that the app "failed to retrieve data" or some such. This is pretty sucky if you ask me.

Using the remote does wake the robot up and bring it back online immediately.

Note that the remote and the app don't know what the other is doing. If you command the robot to start auto cleaning, for example, via the app when it was in the dock, the remote continues to show that the robot is in the dock. It doesn't know that the app told the robot to start cleaning. A lack of synchronisation in this direction is, however, understandable. The remote has an IR transmitter in it, no receiver, so it has no way to receive feedback from the robot.

The same lack of synchronisation also occurs the other way round. If the robot is in the dock and you use the remote to tell it to start cleaning, the app still shows the robot in the dock. Now, that is something that should be updated in real time.

On the positive side, the app does allow you to program auto start times with more flexibility than the remote. You can set up multiple programs that repeat on one or more days of the week and there's no need to have anything in line of sight of the robot for them to work.

Amazon Alexa skill

Amazon uses so-called "skills" to have the Alexa platform talk to third party systems. There is a skill that allows Alexa to link to your Ecovacs account with one or more robots linked to it, to talk to Ecovacs' systems on your behalf and control those linked robots.

Or at least, that's how it's supposed to work.

As things are now, and it appears they've been like this for several months with no fix in sight forthcoming from Ecovacs, Alexa can't see the robots linked to your Ecovacs account, so the skill setup fails.

In other words: "Computer says no"


There are positives and negatives for this particular model.

If this is your first foray into the technology and if you're looking for a budget-friendly solution then this is probably a good solution. If you already have some experience with such robots then this will more than likely be a downgrade that won't impress you. If you have the budget then you might be better off looking at something with laser-based mapping, zoning and maybe the ability to mop clean, a waste receptacle so that the robot can empty itself and a bigger battery.

The app has potential but is very poorly executed. The Alexa skill could be useful if it actually worked (I have no idea how well the Google version for this robot works). Until the software bugs are ironed out, you're better off sticking to the remote rather than using the app. This isn't a big problem because nearly all of the robot's features are covered by it.

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