Black+Decker LST540 Review

product image of BLACK+DECKER LST540 Brushless String Trimmer, 40-volt

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The Black+Decker LST540 is a cordless but (thanks to the brushless motor) very powerful weed eater. It’s capable of performing even lighter and edging tasks, but its disadvantage is a shorter battery time.

  • Powerful
  • Autofeed
  • Easy to assemble and operate
  • Battery time
Key specifications:
Black & Decker Brushless 40 Volt String Trimmer Review (LST540)

Brushless motor

giving your garden a neat look using the LST540The main difference between LST540 and typical cordless weed whackers is the brushless motor – it offers greater power and torque, longer lifetime and less noise, the only disadvantage is a slightly higher initial cost (if you are interested how this motor works, take a look at this article).

Assembly and handling

The LST540 is very easy to assemble – you’ll need just a screwdriver and a few minutes. In contrast with smaller trimmers, it uses steel, not plastic components – so the construction is quite sturdy, but also heavier.

It’s comfortable to operate, you can move the handle to adjust balance and a nice plus is also the telescopic shaft – so taller people can easily set the height as they prefer to avoid trimming in uncomfortable pose.

Power and line feeding

Thanks to the brushless motor and dual line, this Black & Decker offers plenty of power. The speed can be varied depending on how much you push the trigger, which can be a bit awkward unless you get used to it – but then you can save some battery time by cutting on low speeds and speed it up just for occasional bushes or blackberry vines.

While this trimmer excels at medium-harder jobs (it has power similar to gas machines, but it’s a lot less noisy, requires no maintenance or fuel mixing and doesn’t produce any fumes), it can be used for lighter or cleanup tasks as well – however, its size and weight doesn’t make it ideal for those.

The line feeding is ensured by autofeed which is a nice plus – so no more bumping.

Converting to edger


The battery working time is not ideal – users report between 10 and 25 minutes of work, mainly depending on the cutting speed. And that’s a problem – while you’ll a get solid cutting time when doing easy trimming, this machine is designed for harder jobs; but that reduces the time to only 10-15 minutes. And getting a spare battery makes this tool considerably more expensive.

On the other hand, the LST540 is part of the Black&Decker’s new 40V Max lineup – so if you have some machines from this lineup, you probably already have some spare batteries for your new trimmer.

The battery can be easily removed with a click of a button and it takes slightly under one hour to fully recharge. Also, it features a charge level indicator so you know approximately how much power you have left.


As most cordless string trimmers, it comes with an edger adjustment – after pressing a button, the head can be rotated 180 degrees and you can start edging. It works quite well and a metal guide is also present.

Conclusion:  The Black and Decker LST540 is a quality and powerful grass trimmer – but the battery time considerably limits its utilization. You may also want to check out the Greenworks 21362 which has the same power, longer battery time and possibility to use various attachments – but it’s also heavier, uses a bump feed and its edger function is not as good.

However, if you just need a lightweight unit mainly for cleanup or medium-difficulty jobs, consider also the LST136W trimmer.

>> Read more or buy the Black+Decker LST540 here

edging a walkway with the help of the metal guide      detailed view of weed trimming


  • Battery time (according to users): 10-25 minutes
  • Battery power indicator: yes
  • Weight: 8.2lbs
  • Cutting swath: 13″
  • Line: 0.08 dual line
  • Feeding: autofeed
  • Includes: 1 battery, charger, 1 spool

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Frequently asked questions:

How should I treat the battery to ensure maximum lifetime?

Always store the batteries inside your house in reasonable temperatures – never leave them on direct sun or outdoors during winter! Black and Decker also advises to recharge the battery as soon as it is out of power.

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What is included in the package?

The weed eater itself, 1 battery, charger and 1 spool.

Are there any accessories I should buy?

We recommend getting the high quality Cyclone string as a spare line. Replacing just the string is quite easy (see video below) and very cost effective – however, if you would like to use a prewound spool, no problem. Also, if you have a larger yard, consider buying a spare battery.

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Is there any maintenance needed?

No, the motor is an enclosed unit so no maintenance is required. Just ensure a proper care to the battery (see above) and clean the machine from dead grass occasionally.


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