Black and Decker 38cm CLM3820L2 Review – Cordless Mower

Black and Decker 38cm CLM3820L2 Review
Performance/Cut Quality
What I Like
Great performance and reliability
Two batteries supplied for longer run time
Good range of 6 cutting heights from 30mm to 80mm
Fast charging time
The battery is interchangeable with other BLACK+DECKER cordless tools
What I Don't Like
Grass collection box a little smaller than competitors
Slightly more expensive than some similar models
Slightly heavier than some competitors
My Overall Rating


BLACK+DECKER 38cm CLM3820L2 Review

The BLACK+DECKER 38cm CLM3820L2 is a cordless lawn mower, supplied with two 36v 2.0Ah batteries that charge in around 90 minutes and produce 60 minutes of run time. It has a 35 litre grass box, a 38 cm cutting width and 6 cutting heights that range from 30mm to 80mm. The BLACK+DECKER 38cm CLM3820L2 lawn mower is best suited for medium to large sized lawns up to 600m².

Black+Decker have been around for many years here in the UK and were the first to design and produce the cordless drill. Today they are known as a mid range brand that produce a wide range of power garden tools that perform well and are reasonably priced.

So what about this BLACK+DECKER 38cm CLM3820L2 cordless lawn mower? In this review I will take you through the features of this mower and compare it to other models from Bosch and Hyundai. I will also be covering the good and not so good aspects of this cordless mower from Black+Decker, so you know exactly what you are getting for your money.

The BLACK+DECKER 38cm CLM3820L2 is a reasonably priced when compared to other similar sized mowers from other brands such as Hyundai, and like all cordless mowers will save you the hassle of cords and eliminate the tasks associated with adding petrol and oil.

So on paper this mower looks like a real contender, if you are looking for a medium deck sized mower that can cut a lawn up to 600m² with the 2 batteries supplied. Let’s take a closer look at the features and functions of this mower and how well it performs.

Main Features

    • Rating: 9.5/10
    • Covers areas reaching 600m² in size
    • 2 x 36V 2.0 Ah battery
    • Blade length: 38cm
    • Weight: 16.2kg
    • Number of Cutting Heights: 6 (from 30mm to 80mm)
    • Grass box capacity: 35L
    • Charge time: 90 minutes
    • Free run time: 50-60 minutes

BLACK+DECKER 38cm CLM3820L2 Video

To give you a visual representation of the BLACK+DECKER 38cm Cordless Battery Powered Lawn Mower please watch the video below:



Features In Detail

Power System

Lithium-Ion battery technology has improved significantly over the last few years ensuring cordless mowers can compete well with corded and petrol mowers. Yes, they are not going to be as powerful, but they have other advantages that, more than, make up for this.

Having said that, this BLACK+DECKER 38cm CLM3820L2 comes supplied with two 2Ah 36v lithium-ion batteries that will give this mower a run time of up to 30 minutes per battery. That’s a whopping 60 minutes of operating time that will allow you to cut a lawn up to 600m², bare in mind the size of a tennis court is around 260m².

Is the charge time better or worse than its competitors? Well, it’s very comparable really. The single 2.5 Ah 60V battery on the Hyundai HYM60LI380 38cm has more or less the same charge and run-time as this BLACK+DECKER, and as for the Bosch, the BLACK+DECKER actually outperforms the Bosch Rotak 37 LI that charges in 140 minutes and produces around 40 minutes of run-time.

The noise level on this mower is 96 dB(A) and is comparable with similar sized mowers, and as with all cordless mowers they are relatively quiet compared to their petrol counterparts. If you are looking for an even quieter cordless mower, then take a look at the pro-silence feature on the “Generation 5” models of Bosch mowers.

So in terms of the power system on this BLACK+DECKER, all looks good so far and compares very well to other brands.

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As with most mowers sold online, the BLACK+DECKER 38cm CLM3820L2 comes almost completely assembled. All that’s needed is for the handles to be attached, and the grass collection box to be assembled. The instruction manual shows how to do this and I have added a video below that shows how quickly and easily the assembly of the mower is.

As with all solid grass collection boxes, the assembly can be a little tricky, just persevere and you will get there, and once it’s done, that’s it.

Blades and Cutting Diameter

This lawn mower has a fair sized deck with a generous 38cm cutting width that almost cuts right to the edge. I would class a 38cm deck as the upper end of a medium blade or deck size, so this mower is not suitable for small lawns or lawns with very narrow strips.

BLACK+DECKER even make a larger version of this mower, the BLACK+DECKER 48cm CLMA4820L2. This is a huge beast that not only cuts and collects, but also has the ability to mulch and side discharge the grass cuttings.

The blade on this mower gives a clean and precise cut, and as you would expect, replacement blades are readily available and reasonably priced. Anyone with basic DIY skills and tools will also be able to sharpen the steel blade.

Last update on 2024-04-18 / Affiliate links / Images from Amazon Product Advertising API

As long as you don’t have a small lawn, the 38cm deck size is going to get the lawn cut quickly without compromising on manoeuvrability that you are likely to experience with an oversized mower.


Height Adjustment

BLACK+DECKER 38cm CLM3820L2 Height Adjustment

Height adjustment is very important as you will need to change this from time to time. The season, the weather, the type of grass and your own specific requirements will determine the height you want to cut at.

Fortunately, the BLACK+DECKER 38cm CLM3820L2 gives you a range of options (6 height settings) and you can adjust the height from 30mm to 80mm.

This is a good range of height settings, however it would have been nice to have a slightly lower setting of around 20-25mm. This is only necessary if you want a really low, bowling green cut. Cutting your lawn too low can cause issues as the lawn will struggle to obtain enough natural light and nutrients. This mower does however have a higher 80mm height setting, allowing you to easily cut grass that has been left to grow longer.

The lever is mounted centrally making adjustment of all 4 wheels quick and easy.

Roller (Stripes)

There is no rear roller on this BLACK+DECKER 38cm CLM3820L2, so will not produce a striped lawn appearance.

Grass Box Capacity

BLACK+DECKER 38cm CLM3820L2 Grass Box

The grass box has a good 35 litre capacity that is adequate for a mower of this size. The similar Bosch mower comes supplied with a 40 litre collection box and the Hyundai with an even larger 45 litre box. In comparison, the grass collection box on this BLACK+DECKER 38cm CLM3820L2 may seem a little small compared to its rivals, however, please bare in mind that a fully laden 45 litre grass box will add significantly to the weight of the mower. So bigger is not always better!

There is a handy full indicator flap on the box to let you know when you need to empty.

The grass box is a solid plastic construction all round that comes supplied in two halves and needs to be assembled.

The advantage of this type of grass box is that it is not prone to tearing as with cloth collection bags, however the downside is that the solid collection box will not fold flat for better storage and transportation. Yes, the grass box can be broken down into two pieces, however you are unlikely to do this after every outing as it is a little fiddly and time consuming.

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The BLACK+DECKER 38cm CLM3820L2 is practical mower because like all cordless mowers, there is no cord to tether you to the mains socket. This means the mower can be manoeuvred easily and freely around the garden with no problems. This mower is also ideal to be used in areas where there is no mains supply, such as allotments and remote gardens.

The handles fold flat, both half way down and at the lower section, this helps to reduce storage space and again makes transportation easier.

There is also a handy carry handle that is mounted centrally and is positioned well for a balanced lift.

One thing I will say about this mower, it is a little heavier than some of the competition. It’s not that noticeable on flatter and less hilly lawns, but if you have steep inclines then it is worth noting.

Weight Comparison Table

BLACK+DECKER 38cm CLM3820L216.2kg
Bosch Rotak 37 LI Ergoflex13.2kg
Hyundai Cordless 38cm HYM60LI38012.8kg

Save £33.05
BLACK DECKER Lithium ion Lawn Mower Cordless 36V 38cm Includes Two...
  • Cutting mechanism: rotary/metal blade. Supplied with two powerful 36V lithium batteries for gardens up to 600m with charge indicator
  • Easily height adjustable with 6 heights from 30 to 80mm
  • Sturdy, easy to empty 35L grass collection Bin, cutting heights mm
  • Fast and compact storage Thanks to the retractable handles
  • Integrated handle makes lifting and moving easier. Sound power 96 decibel/ ampere

Last update on 2024-04-18 / Affiliate links / Images from Amazon Product Advertising API

Safety Features

BLACK+DECKER 38cm CLM3820L2 Grass Box

In order to start the BLACK+DECKER 38cm CLM3820L2, you need to use the safety key which straight away makes it safe from accidental starting.

The other safety feature, that is standard on most mowers, is the two hand safety button to prevent the machine being started accidentally. As soon as you let go of the start lever, the motor stops immediately.


This feature is not available on this model which is pretty standard for lawn mowers in this category. The larger BLACK+DECKER 48cm CLMA4820L2 does have a mulching ability as well as side discharge.

BLACK+DECKER 38cm CLM3820L2 User Manual

You can download the BLACK+DECKER 38cm CLM3820L2 user manual guide here.

What’s Included in the Box

Included in the kit you with receive the following:

  • Black & Decker CLM3820L2 36v Cordless Electric Mower
  • Two 36v 2.0Ah Batteries
  • One Fast Charger
  • The 35 litre hard grass collection box
  • A user manual

Pros and Cons

As I said earlier, there are many advantages to this lawn mower but there are a few downsides. Let me explain both so you know what you are getting and if this is the best option for you.

  • Two batteries supplied for longer run time
  • Good range of 6 cutting heights from 30mm to 80mm
  • Suitable for larger lawns up to 600m²
  • The battery is interchangeable with other BLACK+DECKER 36V cordless battery tools
  • Good safety features with key start
  • Generous 38cm cutting width
  • Super easy height adjustment
  • Foam covered comfortable handles that can be folded flat for storage
  • A trusted brand with good after sales service
  • Good 2-year warranty
  • Spare parts and support readily available in the UK
  • No hassle with petrol and oil
  • Freedom of not having a cable to worry about
  • Slightly heavier than some competitors
  • No rear roller for a striped lawn
  • Grass collection box a little smaller than competitors
  • No lower cutting height option under 30mm



BLACK+DECKER 38cm CLM3820L2 Grass Box

The BLACK+DECKER 38cm CLM3820L2 really is a serious contender, apart from the minor cons detailed above, it will make a great purchase. Remember this mower is coming in at around £40 cheaper than the Hyundai and both are very similar in terms of features and performance.

The batteries charge in a reasonable time and provide up to 1 hour of run time to ensure you get the job done without having to keep stopping to recharge.

Yes, the grass collection box is a little smaller than the competition, however it means the mower will never be too heavy with an overloaded collection box.

BLACK+DECKER give this mower a good two year warranty, help and support is easily available via their support website and helpline. This is something cheaper brands do not provide, not to mention the availability of replacement parts.

This mower is designed to cut nearly the size of three tennis courts, so great if you have a larger lawn. But, this mower is equally just as suitable for smaller gardens. With its foldable handles and small footprint, storage needn’t be a concern.

The removable safety key will give you peace of mind around children, and the fact of being cordless means it is inherently safer as there is no power cord to run over.

The quality of cut is very good and precise, the mower never seems to struggle for power. Of course you need to ensure you are not cutting too low for the conditions, and start at a higher setting and work your way down should the grass be too long.

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Should You Buy This BLACK+DECKER 38cm CLM3820L2?

BLACK+DECKER 38cm CLM3820L2 Review

If you have a lawn under 600m² and the cons mentioned above do not impact you, then this mower may well be a great purchase.

BLACK+DECKER is a brand you can trust, they have been around for over 100 years and will be around for many years to come. The BLACK+DECKER 38cm CLM3820L2 is their best selling cordless mower and is suitable for so many different types and sizes of lawn. As this mower is provided with two batteries as standard, it will for sure avoid any interruptions.

There are a few factors to consider first, whether or not you purchase this BLACK+DECKER model really depends on your garden and situation.

To give you some guidance on which type of customer would suit this model best, below I’ve listed the categories they fall under:

  • People with gardens up to 600m² in size.
  • People who do NOT need a striped lawn.
  • Those who want a fast battery charge time (90 minutes).
  • People who want generous 6 cutting heights that range from 30mm to 80mm.
  • Those who like the convenience of having no power cord or have limited or no access to a power source in the garden.
  • People who like to purchase a trusted brand with good after sales support.

Of course you don’t need to fall under every category mentioned above, it’s more a guide to whom this mower would be most suitable for. If purchased, I’m sure you will make use of all the features and benefits of this mower, and that it will help to make your lawn mowing experience easy and trouble free.


Where Should I Purchase This Mower?

Save £33.05
BLACK DECKER Lithium ion Lawn Mower Cordless 36V 38cm Includes Two...
  • Cutting mechanism: rotary/metal blade. Supplied with two powerful 36V lithium batteries for gardens up to 600m with charge indicator
  • Easily height adjustable with 6 heights from 30 to 80mm
  • Sturdy, easy to empty 35L grass collection Bin, cutting heights mm
  • Fast and compact storage Thanks to the retractable handles
  • Integrated handle makes lifting and moving easier. Sound power 96 decibel/ ampere

Last update on 2024-04-18 / Affiliate links / Images from Amazon Product Advertising API

Click for Best Price



Does the BLACK+DECKER 38cm CLM3820L2 come with two batteries?

Yes, 2 x 36v 2.0Ah batteries are supplied along with the charger

What size lawn is the BLACK+DECKER 38cm CLM3820L2 designed for?


Is the BLACK+DECKER 38cm CLM3820L2 self propelled?

No, this is a push mower.

Can I put both batteries into the mower at the same time?

No, you need to manually swap the batteries when the first runs out.

Is this BLACK+DECKER 38cm CLM3820L2 available without the batteries?

No, this mower comes supplied with two batteries only.

How many safety keys come supplied with this mower?

Only 1. Spares can be purchased from BLACK+DECKER.

Does the BLACK+DECKER 38cm CLM3820L2 leave stripes on the lawn?

No, there is no roller with this mower.

Does the BLACK+DECKER 38cm CLM3820L2 have a mulching function?


Do the batteries fit other BLACK+DECKER tools?

Yes, other 36v power tools from BLACK+DECKER.

Does the BLACK+DECKER 38cm CLM3820L2 cut to the edge?

No, it cuts close to the edge. This is common with all mowers.

Not sure about this mower? Click here to see more Cordless Lawn Mower Reviews.

Additional Specifications

Additional Specifications
Working Area 600m²
Cutting width 38cm
Cutting height steps 6
Cutting height max 80mm
Cutting height min 30mm
Cutting height adjustment Central
Collector volume 35L
Battery Type 2 x 36V 2.0 Ah batteries
Typical Charging Time Charge time: 90 minutes
Typical Mowing Time 60 minutes (600 m²)
Vision Window No
Right or left start switch Left and Right
Foldable handles Yes
Battery power indicator Yes
Grass bag filling indicator Yes
Roller No
Dimensions 76 x 46 x 43.8 cm
Weight 16.2 kg

Lawnmower Product Expert, Reviewer and Author at | 01284 615144 | | Website | + posts

As a seasoned expert in the field of garden power tools, I have dedicated over a decade to working with and reviewing a wide variety of lawn mowers. My extensive experience has allowed me to gain a deep understanding of the benefits and limitations of different types of mowers and garden tools.

Over the years, I have honed my skills in writing informative articles and creating helpful videos for various blogs and publications. This has given me the ability to not only recognise what makes a good lawn mower, but also to help you choose the perfect garden tool for your specific needs and requirements.

With my wealth of knowledge and expertise, I am confident that I can provide you with valuable insights and recommendations when it comes to selecting the right lawn mower for your lawn. So, whether you're looking for a battery cordless, electric, petrol, or robotic mower, you can trust in my expertise to guide you towards the best option for your garden.

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