Cobra MX46S40V Cordless Lawnmower Review

Cobra MX46S40V Cordless Lawnmower

We’ve reviewed cordless chainsaws, lawnmowers and cleaners. In general we’ve found no compromise in the performance when compared to their chorded electrical siblings. Outdoor appliances can even remarkably supersede petrol too, which we’ve witnessed with the high performance cordless EGO Power+ Chainsaw. However, this new shiny Cobra MX46S40V cordless Li-ion lawnmower elevates the benchmark of how and where cordless can go. It features a 40V performance, making it the 'on paper' highest voltage cordless lawnmower we’ve yet to try, and this is coupled with a big box of features, the most notable of which is a self-propelled drive.

Design & Features

Anyone glancing at this Cobra cordless lawnmower could easily jump to the conclusion it was petrol based due to its thick red steel body. With a closer inspection it would become evident that something else was going on, as no engine is this clean in appearance, and it is the motor and batteries that are enclosed within the neatly shaped rugged plastic on top of the mower; the batteries being accessed through a door.

The gutsy steel body adds significant weight and is our greatest beef with the Cobra MX46S40V, as it totals a hefty 29kg. Despite an integrated carrying handle it’s a mammoth strain to carry over steps, which is a necessity for us as some of our lawns can only be accessed this way. Though we can safely say that, from our four weeks of using the Cobra lawnmower over all kinds of irregular terrain and jarring it into dozens of bushes and stones, it still looks as good as new and the paintwork, when inspected close up, isn’t at all scratched from cutting under bushes. We particularly liked the fact that tough plastic has been used as a bumper along the front of the mower; the area that tends to take a lot of impact.

Cobra MX46S40V Cordless Lawnmower Grass Bag Side View

As far as lawnmowers go, this offers a full range of features that bring it into a premium class against similar competition. The previous cordless lawnmowers we’ve reviewed from both Black & Decker and Einhell were top of the line models and weren't short of features, offering similar ease of use, but the Cobra MX46S40V has everything these have (except an easy to fold down handle) and quite a lot more. Two bundled accessories found in the box allow for mulching and for the grass to neatly discharge alongside the mower. What’s more, it boasts battery indicators on the handle, a self drive, a 46cm cutting width, a 60ltr grass bag, a quick action 7 stage (25 - 75mm) height adjustment lever and large rear wheels. On paper all this, coupled with no wires or petrol, is a lawn enthusiast's dream.

Cobra MX46S40V Cordless Lawnmower Height Adjustment

Battery Life & Charging

One of the key differences between the Cobra MX46S40V cordless lawnmower and all our other cordless lawnmowers, is the ability to display the level of charge for each battery on the handle. Whereas with other cordless mowers we had to stop mowing, open the battery housing door and frustratingly press the battery for a readout of the charge, this bright LED readout, conveniently centred in the middle of the handle bars, gives instantaneous feedback, and it took no time at all for it to be an embedded and informed habit of mowing.

The Cobra MX46S40V comes with two batteries but only one charger. Cobra claim these Samsung 40V lithium-ion batteries don't have a 'memory effect', where the charge capacity deteriorates with use. Initially we thought the mower ran on two simultaneous batteries, but later realised that it holds two whilst only ever using one for power. So if you start with two full batteries and one runs out, you can charge it whilst using the remaining full one. Charging each battery, once all the power is diminished, always clocks in at around the two hour mark from our experience. We haven't yet had much opportunity to test how effectively the batteries hold their charge, but after leaving them idle and fully charged for one week, they did not drop below the full level.

Battery life is obviously one of the most, if not the most, important aspects of a cordless product. Giving a definite answer to how long they hold a charge is hard, as there are so many variables that impact on the time they last. As a good rule of thumb the Cobra, with two fully charged batteries, cutting a respectable 5-6cm of grass, will return 70 minutes of runtime if using the self-propelled drive sparingly. If the drive is constantly used it will eat into the battery life by around 50%, leaving an 30-35 minutes of battery to play with. So basically, for bigger lawns like ours, where at times recharging batteries delays progress, the Cobra MX46S40V cordless mower is an ideal fit, where we can get everything cut in one convenient run.

Cobra MX46S40V Cordless Lawnmower Battery Compartment

Usability & Self Propelled Drive

Cobra are trying admirably hard to make sure absolutely anyone's hands are comfortable whilst pushing and holding down one of the power buttons. We say 'one of the power buttons' because four individual power buttons are scattered under the pleasantly rubberised handle, as seen within our below photo.

Cobra MX46S40V Cordless Lawnmower Handle Buttons

Nevertheless, the increased raw power, dimensions and 29kg weight do add far more strain for the user, relatable more to a petrol lawnmower. Putting the mower away in a tightly packed shed is cumbersome and any lifting is a straining task. Yet, when mowing, all this heaving can be counteracted with the press of a lever on the handle. We’re referring to the self-drive, of course, something we have found to be pure torque that won't give up for anything. Initially we used the self-drive a lot, but then noticed it does cut into the battery life by roughly 50%, and it’s slower than our normal pace of walking anyway, so we use it only when we really need to. For instance, the Cobra often gets stuck on our grounds when being pushed on slopes, and a press of the self-drive gets it quickly moving forward; furthermore, it saves us from breaking into a sweat  when going uphill. Added to its ease in use, pushing the mower without utilising the self-drive over level ground isn’t overbearing because the rear wheels, being significantly bigger than the front, assist it in a forward direction.

Cobra MX46S40V Cordless Lawnmower Handle

Cutting Performance

On paper the Cobra MX46S40V is the most powerful cordless lawnmower we’ve tested, but did it seem this way? Well, to answer that, it certainly did. However, the higher RPM of the blade, in contrast with the Einhell and Black & Decker cordless mowers, meant increased noise. It’s rated at being 96dB, around 6dB louder than the previous cordless mowers to which we've been accustomed. It’s not dramatic, but this slight increase in noise level make it harder to talk over or hear the general surrounding environment, although doesn't cause ear fatigue.

Cobra MX46S40V Cordless Lawnmower Side View

The raw power is exceptionally impressive and make this a true contender against even some of the punchier petrol lawnmowers currently on the market. We have noted that some kind of gearing or software tracking the strain the motor, is definitely occurring. When we’re mowing shorter and less intense grass we can hear the motor calm down, and whenever we introduce it to thicker and longer grass, or even ground with twigs and similar debris, the motor can plainly be heard ramping up the power. This is a sensible and really admirable system, as it automatically optimises the battery's charge. We have big praise for this system as it has never been caught out and the mower hasn’t ever noticeably shuddered under the strain of thick overgrown grass; even of 18cm in height. In fact, where we’re located there are many pine cones that we’ve accidentally repeatedly run over, and the mower just obliterates them in 1-2 seconds.

The expansive 46cm cutting width makes quick work of mowing grass, but that width does come with some drawbacks on uneven lawns. Lumpy and textured ground can cause the blade to catch the grass too low at the centre point, leaving white patches - this is, of course, due to the wider wheelbase. Adjusting the cutting height can overcome this, but will leave the grass longer overall. Assuredly changing the cutting height is so easy to do via the adjusting lever, that if your lawn has only one or two uneven levels, you can prepare for these easily. Obviously the white areas will return to fresh green, but you may want to consider the wheelbase associated with the cutting width if you’re meticulous about your uneven lawns. Conversely, on flatter lawns the Cobra MX46S40V shined as a dazzling example of a swift tool for the job, leaving a smooth and even cut. Indeed, the battery life appears to be prolonged by the wide cutting width and it saves substantial mowing time when compared with the Einhell and Black & Decker cordless mowers with their 36cm-38cm cutting widths. 

Cobra MX46S40V Cordless Lawnmower Grass Cutting Performance Quality

Mulching and Grass Collecting

We primarily collected our cuttings within the large 60ltr grass bag, which we found easy to take off and reattach. The side discharge tool fixes under the right side flap on the mower and is extremely practical to use if your grass grows to excessive lengths.

Cobra MX46S40V Cordless Lawnmower Side Discharge Shoot

If you’re into mulching, a plug can be inserted to block the grass from entering into the collecting basket, forcing the grass to be thrown up through the blades and travel back through them, before burying the cuttings within the grass below. Upon taking the Cobra cordless mower out of the box and using it for the first time, we unknowingly had the mulching plug inserted - after cutting roughly 60 square metres of grass, we went to check on how full the basket was getting and, to our surprise, it was empty. The mulched grass was so fine and deeply planted into the cut grass that we couldn't see it at all.

Cobra MX46S40V Cordless Lawnmower Mulching Plug


Even though this is one of the heavier and larger cordless mowers out there, Cobra have preserved the charm and freedom that cordless mowing provides for the price of £450. After all, this has a big box of features; not gimmicky but truly offering a wholesome purpose. We would question whether the steel body was necessary, as it adds so much weight, but certainly the self-propelled drive has proved itself useful and keeps this sizeable mower going in straight lines regardless of the task. Finally, and really importantly, it's a cordless lawnmower that dishes up a dependable two hours of constant mowing which, coupled with a wide cutting width, really positions itself as an accomplished product for cutting large lawns with no charging intervals necessary.