BLACK+DECKER CM2040 20″ Cordless Electric Mower Review

BLACK+DECKER CM2040 20″ Cordless Electric Mower Review
8 Total Score
  • Starts quickly
  • Impressively quiet
  • Light enough for anyone to use easily
  • Versatile clipping-disposal options

The Black & Decker CM2040 Cordless Electric Mower checks off positive box that makes an electric mower worth considering over a more sturdy and versatile gas-powered model. Unfortunately, it accomplishes precious little more beyond the status quo expected of its class.

That isn’t to deem it an ineffective design. Far from it. Overall, it boasts an admirable set of useful features and maneuvers easily enough to make a fine first mower for a first-time homeowner. It even performs fine within the given limitations imposed by its build, but those limitations are fairly narrow. It does everything one could reasonably expect from an electric mower. However, I would be remiss not to point out that, while several competing models may weigh and cost a bit more, you have options within the same category that go just a bit farther above and beyond par.

Key Features

  • Comes with two 40-volt Lithium batteries – each good for up to 30 minutes of mowing time
  • Black 20-inch deck
  • Patented AutoSense technology detects thickness of grass and adjusts variable-speed mower’s velocity accordingly
  • Shielded onboard compartment holds both working battery and spare
  • Push-button start with removable safety key
  • Bailing lever instantly kills engine when released in case of emergency
  • Six adjustable height settings
  • Optional mulching and bagging attachments
  • Three-year warranty


The CM2040’s pair of 40-volt Lithium batteries each power approximately 30 minutes of whisper-quiet use, roughly the lower end of an “average” range of cutting time for most consumer battery-powered models before you either turn to a backup or consider your mowing day finished. With that in mind, never forget to fully charge both batteries the evening before you plan to mow. The included charger takes up to two hours to fully power up each battery. By comparison, a number of competing mowers need only about 45 minutes. Ouch.

Virtually every cordless electric mower shares an Achilles’ heel: cutting power tapers off toward the end of a battery’s charge. Considering that the CM2040 doesn’t exactly produce overwhelming overall power even with a fully juiced battery, it performs relatively pitifully after around a half-hour of cutting. If you have an especially small lawn with relatively light grass, a corded mower would provide a more dense, consistent power supply without making finite working time a factor in finishing the job.

Ease Of Use

If nothing else, the CM2040 is damn user-friendly. Weighing in at 43.5 pounds, even younger and less physically hardy adult users alike will have no trouble pushing it around more easily than other electric mowers listed up to 13 pounds heavier or bulkier gas mowers that equal its 20-inch deck measurement but outweigh it by a solid 50 pounds or more.

Like almost any electric mower, it also starts up with a responsiveness few gas-powered peers can match, if any at all. Just insert an adequately charged battery, hit the push-button starter, hold down the bailing lever and off you go. In case you don’t expect to finish in under 30 minutes, a shielded onboard compartment stores both your working battery and a spare to swap in on the spot.

This is also quite a considerate mower when it comes to monopolizing as little real estate as possible when not in use. Four quick-release levers located on the handle allow it to fold down and save incredible space. Any dedicated lawn jockey who already owns enough tools to fill a hardware store can undoubtedly appreciate a little more walking space inside a shed or garage.

Cut Quality & Options

The CM2040 passes muster with flying colors on small-to-medium lawns with no more than moderately thick grass around two to three inches tall. That’s about the threshold of its wheelhouse where it dependably leaves behind a smoothly manicured finish. The variable-speed motor’s unique AutoSense technology detects the thickness of the grass beneath it and intuitively adjusts blade velocity accordingly to provide the smoothest possible cut. Employing a single lever to adjust deck height among six settings between 1.5 and 4 inches makes adapting to taller grass or uneven ground an efficient, simple proposition. As for clipping disposal, you have the option of simply ejecting remnants of grass through the side-discharge chute, using the mulching attachment to return valuable nutrients to your lawn while you cut or using the included 15-gallon bag with the rear chute to keep your clippings until you decide to stop and rid yourself of them as you choose.

Again, I cannot recommend this mower for larger-scale jobs. The CM2040’s issues with big lawns stretch beyond only offering 60 minutes of work at most with two fully charged batteries. When faced with especially thick grass, the engine has a frustrating tendency to stall and the cutting mechanism struggles to properly eject, mulch or bag clippings. There’s just no reason to overwork this diminutive mower made for more modestly sized spreads when a gas mower or even an electric with more muscle and longer battery endurance.


There isn’t much to note as far as maintaining the CM2040. Keep the batteries both fully charged before you cut. Sharpen the blades several times each season. Finally, avoid overexerting it against oversized lawn and thick, stubborn greenery. Should anything break down otherwise, Black & Decker backs it with a generous three-year warranty supporting repairs and replacement under most incidental circumstances.

Safety Features

If there’s one thing that makes parents particularly nervous about mowers with push-button starters, it’s the thought of a wayward tyke getting curious and accidentally setting the blade in motion. Being a parent myself, that’s why I can so easily appreciate the removable safety key needed for the button to activate the engine. When in use, releasing the bailing lever instantly kills the engine in the event the mower should slip the user’s grasp or an unexpected hazard should enter its path.

Cost Effectiveness

Provided you aren’t exactly grooming the greens at Augusta, you could do a lot worse spending under $400 to maintain a smaller lawn. The CM2040 is a perfectly capable machine within its engineered limitations, but don’t push its luck, even with a three-year warranty. As a bonus, its pair of batteries are engineered for cross-compatibility with most cordless Black & Decker lawn and garden tools, potentially improving the usability of your mower’s supporting cast of landscaping equipment at no “extra” cost.

8 Total Score
Boasts an admirable set of useful features

  • Starts quickly
  • Impressively quiet
  • Light enough for anyone to use easily
  • Versatile clipping-disposal options
  • Lackluster power
  • Batteries take two hours to charge
  • Underwhelming performance against thicker grass
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