Black and Decker LST420 ReviewAfter five years of struggling to get any more than 15 minutes of use out of my old battery-powered Black and Decker Grasshog electric trimmer I was ready to bite the bullet and take my chances with a gas trimmer.  While I was searching for decent trimmers I came across the Black & Decker 20V Max Lithium High Performance 12-Inch Trimmer and Edger. A new model of electric trimmer is not particularly unexpected, but what was surprising was the rave reviews and a price that was under $100. I like the idea of battery-powered yard tools.  They’re generally a little quieter, you don’t have to fight with cords, they’re cleaner to operate, they don’t pollute and they shouldn’t cost as much to use.  But like a lot of people I’ve been burned with electric tools with batteries that don’t last long, don’t offer a lot of power and tend to only last a year or two.

So it was with a bit of trepidation that I ordered a 20 Volt Black & Decker electric trimmer and edger from Amazon last weekend.  I ended up getting the LST400 Lithium High Performance Trimmer, though there’s also an LST420 model trimmer.  The trimmers look pretty much identical at first glance.  The LST400 comes with one large battery while the LST420 comes with two smaller batteries.  The LST420 is also about 8 ounces lighter.  Otherwise, they’re the same trimmer.

The Black & Decker LST400/LST420 20 Volt Trimmer.

The Black & Decker LST400/LST420 20 Volt Trimmer.

For my testing grounds I used my fairly typical suburban yard.  Most of my trimming is cutting down high grass along the edges of fences and flower beds.  In the spring and late summer I sometimes have to cut down some heavier weeds and over growth behind my shed, but it’s mostly limited to one or two small areas.  So how did it do?  Let’s look at a couple areas:

Assembly and Set Up

The trimmer comes mostly assembled with one two real “assembly” steps.  The grass shield needs to be attached with a screw and the handle needs to be put on with a thumb screw.  The entire process, from opening the box to putting everything together took me about four minutes.  Really.  You can check out the unboxing and assembly video.

Unfortunately, the battery doesn’t come charged, so I had some time to kill before I could take my trimmer out for a test run.  Because I picked up the LST400 with one large battery, the initial charge time took about 8 hours.

Trimmer Power

The Black & Decker 20 volt high performance trimmers actually have two speed settings.  Speed 1 runs the trimmer at 5500 rpm, Speed 2 increases the speed to 7200 rpm.  The lower speed setting worked well for all my tall grass and I didn’t actually notice much of a difference the few times I increased the speed for testing purposes.  Speed 1 is plenty fast and powerful enough to whip a piece of plastic line through just about patch of tall grass, so that wasn’t really an issue.  There’s almost no vibration (another advantage over gas trimmers) and for basic yard maintenance it did everything it was supposed to do.

Comfort and Ease of Use

All of the Black & Decker electric trimmers are relatively light, weighing about 7 pounds or less.  The LST400 and LST420 models have adjustable length shafts, but they do go a little longer than previous models, so tall people can rejoice and not have to stoop over so much.  There is somewhat adjustable grip on the shaft and the handle with the power button is large and comfortable.

The Black & Decker trimmers have an “auto feed” function which somehow (magic?) keeps the line coming out without having to bump the bottom.  It’s a neat trick and it generally works well.  That being said, you CAN still manually bump the head on the ground to kick out more line when you need it.

The line swings out in an arc which gives you about a 12 inch cutting path which is perfectly acceptable for most suburban yards.

The overall light weight of these trimmers make them a good choice for people who don’t work outside a lot or don’t want to struggle with a heavy machine.  There is some vibration, obviously, but it was manageable and generally ran pretty smoothly.  There’s no shoulder strap or harness, but these trimmers are light enough that you generally don’t need one.

As for quality, only time will tell.  These trimmers are mostly plastic with a few key metal parts (the shaft) and they don’t feel as solid (or as heavy) as some professional grade lawn tools.  Though plastic is not my first choice when look at lawn tools I have to admit that the Black & Decker tools usually last a while if you take care of them.

I’d have no problem allowing my retired mother use this trimmer.



The LST400 offers a clever and unique edging wheel.

What makes these electric trimmer and edgers stand out in a store display is the bright orange wheel that’s affixed to the trimmer head.  The wheel works as a sort of guide when you’re trimming around fences and flower beds, but it really shines when you twist and turn the head into edger mode.  I’ve never really edged my sidewalks or driveways before, but the wheel made it pretty easy.  I just rested it one the ground, pulled the power trigger and rolled down the sidewalk in a straight line.  My initial edge wasn’t perfect, but it was darn close and it was really easy to do.

I initially purchased the Black & Decker LST400 purely for the trimmer function, but I think the edging wheel alone has convinced me that I need to edge my sidewalks and curbs a lot more often.

Battery and Power Usage

I know, this is what you’ve been waiting for.  Again, I picked up the LST400 model which has the single larger 20 volt lithium battery pack.  That battery took about 8 hours to charge initially but then it lasted for a good 50 minutes or so of solid trim time at the 5500 rpm speed before I thought I could feel the power begin to drop a little bit.  That’s impressive and it meant that I could trim my entire yard and get some edging in all with a single battery charge.

On the Speed 2 setting other reviewers are reporting a dependable 25 to 35 minutes of cutting time, which is still a lot more impressive than the electric trimmers of just a few years ago.

When the you are using the lithium battery it’s best to simply keep it plugged in to the charger.  It will stop charging when it’s full to save energy and by keeping it plugged in you will always have it ready and available.

The battery did get a little warm while using it (about 117 degrees Fahrenheit).  And while that may seem a bit hot, its still a lot cooler than a sidewalk or driveway on a warm summer day.

Video Demo


Overall the Black & Decker 20 volt 12-inch Lithium High Performance Trimmer and Edger is a solid choice for the weekend warrior or homeowner who wants to trim around the house without the hassle of gasoline or a cord.  The trimmer offers decent power, an affordable price and an impressive run time.  Your local big box hardware store is likely to have some variation of these trimmers or if you like having things show up on your door step you can order one directly from Amazon.


If you have any questions about any process, service or tool I review here please feel free to drop me a comment and I’ll do my best to give you an honest answer.

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