Black and Decker CM2040 Cordless Lawn Mower Review

Aaron GreenGarden Power Tools, Lawncare0 Comments

Black and Decker CM2040 Review

We had high hopes when getting the Black and Decker CM2040 out of the box; it looks great, the specs read well on paper and it had the Black & Decker name we all love. Unfortunately after testing it multiple times in different scenarios the CM2040 did not quite live up to our expectations.

Product Features

  • Includes (2) 2.5Ah - 40V MAX Lithium Batteries for longer cutting time
  • 20-inch wide cutting path
  • 6-setting height adjustment from 1-1/2 inch to 4 Inch high
  • 15 gallon nylon grass collection bag
  • Note: Please refer the installation manual for using the clip and the user manual for charging the CM2040 battery

Black and Decker CM2040 Review

Set Up

black and decker electric mower

The CM2040 is light enough to transport easily

Key points:

  • Assembly time of approximately 5 minutes plus battery charge time
  • Handle easily folds out, and folds back away again for easy storage

The Black and Decker CM2040 cordless mower comes almost fully assembled and can be ready to use in around 5 minutes plus charging time.

Simply extend the mowers handle, insert the included bolts and tighten them up.

Storing this mower is easy as the handle folds back over the mower  minimizing the storage space required, it is also very light so it is easily hung up on a wall if that is your preferred storage method.

Battery Performance

Key points:

  • Comes with 2 x 40V 2.5Ah Li-Ion batteries
  • Charging time of 60 minutes per battery
  • Run time of 10 – 30 minutes per battery depending on power
Black and Decker CM2040 comes with 2 x 2.5 AH 40V Li-Ion batteries. One battery is used at a time and the other one is stored in storage compartment on the mower. When the first battery runs out of power it is simply a case of swapping them over, removing the need to go and find the second battery from the garage or shed.

lithium lawn mower

Convenient storage for the second battery

I was not impressed by the battery life that I got out of the CM2040, if I was cutting grass that had only been mowed a week before then I could get 30 minutes run time out of a battery. However, if I was cutting grass that had gotten a little long then the run time went as low as only 10 minutes. The battery life you will get out of this mower is heavily dependent on how hard the work it has to do is.

The batteries in the Black and Decker CM2040 get very hot while in use, so hot in fact that they will not charge immediately after being used! This is a little odd, as the exact same batteries used in a Black & Decker Trimmer do not get anywhere near that hot, but this is no doubt to do with the higher current draw. So you will need to let them cool down before charging them, which in reality means a longer charging time.

Mowing Power

Key Points:

  • Struggles with tall grass
  • More suited to lawns that are mowed regularly

Longer grass is not the CM2040’s friend, in fact it really struggles with anything you have left grow for longer than a week. If you mow your lawn regularly then you probably won’t have any problems, but if you sometimes let your grass grow for longer periods of time before mowing then you will curse the low power of this cordless lawn mower.

I can handle the fact that the mower has trouble cutting longer grass, as a lot of cordless mower do. However the most annoying thing is that when the engine actually stalls (turns itself off) due to the grass being too long or thick, it has a safety feature that kicks in preventing the mower from starting again for a period of time.


black and decker CM2040

The Black & Decker CM2040 is easily pushed up inclines

The first time I used the CM2040 I could swear that I had bought a kids toy, it was so light and easy to push around – it just did not feel like a proper mower! But as I used it more  Feels like a toy at first but is actually quite durable.

The light weight of this mower is great as it is super easy to push around obstacles and up inclines. It also makes it a breeze to lift up and hang on a storage hook if that is your preferred storage method.

Additional Features

Autosense Technology
The theory behind the ‘Autosense Technology’ is that the mower will sense when it needs to adjust the power up, or when it can lower the power and this gives you a longer battery life. The only problem is that most of the time the Black and Decker CM2040 was at full power to cut almost any length lawn resulting in a short battery life.

The mulching mode actually works really well with this mower, the grass clippings are chopped up nice and small and almost no visible trace is left on the lawns when you are finished mowing.

I am not sure whether this is classed as a “feature” but I will mention it here anyway. The way the CM2040 is designed means that the mower cuts right to the edge of the 20″ deck width. Meaning that when you need to mow around obstacles there is only minimal (if any) grass left to hit with the trimmer later.

Spare battery storage
It makes me sound really lazy, but I did love the fact that I did not have to go back to the garage to get the spare battery when the first one ran out. I simply took the spare battery out of the storage compartment and swapped them over and I was up and mowing again.


If the Black and Decker CM2040 had a bit more power and the batteries lasted a solid 30 minutes every time, then the price would be spot on for a 40V mower from a well known brand. Unfortunately I think the price is a bit high for how this mower performs so the value for money just is not there.

Tips for Using the Black & Decker CM2040

  • Don’t let your grass go too long between mowing, this mower does not cope well with long grass
  • If you do find yourself cutting longer grass with this electric mower, set the cutting height at the highest setting and go over your lawn once, then set it at your desired setting and go over it again
  • The batteries used in this mower are compatible with several other Black & Decker cordless tools
  • If you are often mowing longer lawns, you might want to consider a third battery, they are available here.
  • This mower requires very sharp blades to cut evenly – be sure to check this regularly

Black and Decker CM2040 Manual

Looking for the manual for the Black and Decker CM2040? You can download it here.

Essential Home and Gardens Rating
Run Time2
Additional Features5
Ease of use5
Very light and Maneuverable
Storage spot for second battery
Wide range of cutting heights available
20" deck width
Poor battery life
Power is below par
Total Score
The Black and Decker CM2040 looks great on paper, but unfortunately does not perform as well as it should. A lack of power and poor battery life really let this mower down.
Available from Amazon


Last update on 2017-11-21 at 22:44 / Affiliate links / Details

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