Black & Decker 40V MAX Lithium String Trimmer

Why I reached for this 40V trimmer

I wanted a cordless trimmer that could handle weekly yard touch-ups without the hassle of gas, pull cords, or extension cords. The 40V platform promised more grunt than the typical 20V homeowner tools, and the ability to flip into an edger sounded perfect for keeping sidewalks tidy. After a season of use, I’ve formed a pretty clear picture of where this trimmer excels—and where it doesn’t.

Setup and first impressions

Out of the box, assembly is minimal: attach the guard, snap on the auxiliary handle, charge the battery, and go. The included wall‑mountable charger is handy if you like a dedicated spot in the garage. The trimmer ships with a single 40V MAX (36V nominal) 1.5Ah battery and one AF‑100 spool. At 8.9 pounds with the battery, it’s light enough for most homeowners and noticeably less fatiguing than many gas models. The shaft is adjustable for length, and the auxiliary handle has enough adjustability to find a comfortable grip and maintain good balance.

The on‑tool state‑of‑charge indicator is a small but appreciated touch. Knowing how much battery is left before tackling the back fence saves a lot of guesswork.

Power and cutting performance

For a single‑line, 0.065‑inch trimmer, there’s respectable cutting authority. The high‑torque transmission does a good job transferring power to the string, and the two power settings let you tailor output to the task. On the lower setting, I can handle typical grass trimming around beds and fences while maximizing runtime. Bumping up to the higher setting helps with taller, coarser patches and grassy weeds.

Is it going to replace a commercial gas trimmer? No. But for typical suburban yards, it’s more capable than I expected. I’ve cut through weeks‑old growth along a fence line without babying it, and it didn’t feel starved for torque.

One important note: while it’s advertised as a 13‑inch cut, the single‑line head doesn’t feel like a full 13 inches in real‑world use. If you’re used to dual‑line, 0.080‑inch heads chewing through a wide swath, this will feel narrower and slower. You can still get clean results—it just rewards a steady pace.

Edging performance

Converting to an edger is quick—rotate the head and you’re in. For occasional touch‑ups, the edging mode is perfectly serviceable. It’s especially effective along softer turf edges where you’re cleaning up overgrown grass on hard surfaces.

For long edging runs, the limitations show. There’s no support wheel; you’re guiding the tool freehand. The pop‑out edge guide helps you find the line, but it doesn’t carry the weight or keep a perfect path. If you’re used to a dedicated wheeled edger, expect more finesse work from your arms and wrists. I can keep a reasonably straight cut along a driveway, but it’s more effort and concentration than a tool purpose‑built for edging.

Line feed and spools

The Automatic Feed Spool (AFS) mostly does what it promises: advance line without bumping. It’s convenient and keeps the head off the ground, which helps protect the guard and prevents scalp marks. That said, there are moments—especially after cutting heavy patches—when I wish I could bump to get an instant length refresh. The AFS usually catches up after a brief pause or a restart, but the lack of a manual backup is noticeable.

Spool changes are painless and truly tool‑free. The head accepts AF‑100 spools, which are widely available. Keep at least one spare on hand; if you’re doing a mix of trimming and edging, you can go through line faster than you’d think.

Battery and runtime

The included 1.5Ah pack is the right size to keep the tool light, but it sets your expectations on runtime. Working at the lower power setting, I can tidy up front and back yard edges and around obstacles in one go. Add heavier growth or extended edging, and I’m looking for the charger sooner.

A few practical observations:
- Light, frequent trimming maximizes runtime. Quick weekly passes are the sweet spot.
- Heavy cutting and sustained edging drain the pack faster. Plan to charge or pause.
- The tool’s power electronics are good about protecting the battery. If you bog down the head with vines or thick weeds, it will shut off rather than cook the pack; clear the jam and restart.

If you have more than a modest yard, I’d budget for a second battery—ideally a higher‑capacity pack in the same platform. The charger is compact and straightforward; charge time is reasonable for a homeowner tool, but topping up mid‑job isn’t ideal.

Ergonomics and noise

Ergonomically, this trimmer hits a nice balance. The adjustable shaft and handle make it easy to set up for different user heights. Weight distribution is better than many battery trimmers; the head isn’t overly heavy, and the battery counterbalances decently.

Noise is higher than many expect from battery tools. It’s not thunderous, but it’s a sharp, high‑pitched whir at the head that carries. I still wear hearing protection, and I wouldn’t count on it being a “quiet hours” tool.

Vibration is low, especially compared to small gas units. After a full session, my hands aren’t buzzing, which makes it easier to maintain steady technique.

Maintenance and ownership

Maintenance is refreshingly simple:
- Keep a clean guard and head; clippings accumulate fast, especially in damp grass.
- Inspect the spool and line condition; old, brittle line feeds poorly.
- Store the battery at partial charge if you’re putting it away for a while, and avoid leaving it on the charger for days.

Everything about the design favors low‑effort ownership. There’s no carb to winterize, no fuel to mix, and no exhaust fumes. Long‑term, your costs are line, occasional spools, and potentially an extra battery.

What I’d change

A few tweaks would elevate this tool:
- Add a bump‑feed backup. AFS is convenient, but a manual override would solve the occasional “short line” moments.
- Include a support wheel for edging. Even a small, adjustable wheel would improve straightness and reduce fatigue on long runs.
- Ship with a higher‑capacity battery option. The 1.5Ah pack keeps weight down, but many homeowners would trade a few ounces for more runtime.

Who it’s for

This trimmer is a strong fit if you:
- Want cordless convenience for routine yard maintenance.
- Have a small to medium yard and trim weekly.
- Prioritize light weight, simple controls, and fast setup over raw cutting width.
- Plan to edge occasionally, not as a primary task.

It’s not ideal if you:
- Regularly cut dense weeds, tall brush, or neglected areas.
- Need long, straight, professional‑looking edges every week.
- Expect a full 13‑inch dual‑line performance in thick growth.

The bottom line

The 40V trimmer delivers what most homeowners need: enough power to keep grass edges in check, easy line changes, cordless freedom, and a body that won’t beat you up over a Saturday morning. It’s honest about its limitations: a single‑line head, a smallish included battery, and an edging mode that’s best for touch‑ups rather than marathon sessions. The state‑of‑charge indicator, adjustable shaft, and well‑mannered balance make it a genuinely pleasant tool to live with.

Recommendation: I recommend this trimmer for homeowners with small to medium yards who value convenience and low maintenance over maximum cutting width and pro‑grade edging. Pair it with a second battery if your trimming runs long, keep spare spools on hand, and you’ll have a reliable, easygoing yard companion. If your yard routinely throws heavy brush or long edging runs at you, consider a higher‑voltage system or a dedicated wheeled edger instead.