Black & Decker 40V MAX* Lithium String Trimmer (Battery and Charger Not Included)

Why I reached for a 40V trimmer

Electric string trimmers have come a long way, and for day‑to‑day yard maintenance I’ve increasingly preferred cordless over gas. I’ve been using Black+Decker’s 40V trimmer for a full season, tackling weekly grass trimming and the occasional edge cleanup on a small suburban lot. It’s a bare tool—battery and charger aren’t included—so I paired it with an existing 40V MAX pack from the same platform. If you’re already invested in Black+Decker’s 40V system, it slots in neatly. If you’re on the 20V platform, note that those batteries aren’t cross‑compatible.

What stood out early was the balance of simplicity and control: a lightweight build, automatic line feed, and a power dial that actually makes a difference in both runtime and cutting punch.

Setup and compatibility

Out of the box, assembly is straightforward: snap on the guard, fit the auxiliary handle, and load a fully charged 40V battery. The unit ships with a pre‑wound spool (AF‑100) and the usual safety guard. At 6.5 pounds without a battery, it’s easy to manage. With a mid‑capacity 40V pack, it still feels light enough for anyone to handle comfortably.

Two practical notes:
- It’s a bare tool. Plan for the added cost of a 40V MAX battery and charger if you don’t already own them.
- The head uses 0.065‑inch line and a single string. It’s ideal for lawn trimming but not built for heavy brush or woody weeds.

Power and cutting performance

A dial on the handle lets you choose between more power or more runtime. On low to mid settings, I trimmed lawn edges and fence lines cleanly without burning through the battery. On high, the trimmer had enough bite to knock back thicker patches of grass and the start of weed stems, though that setting shortens runtime significantly.

Black+Decker’s geared transmission (their “POWERDRIVE” marketing term) deserves some credit here. It keeps the head from bogging down as much when you graze denser spots. I left the dial in the mid range for most work, bumping up to max for quick bursts through trouble patches.

The cutting swath is right around a foot—plenty for residential trimming. Being a single‑line design, it’s not as aggressive as dual‑line heads you’ll find on pro trimmers, but it’s also easier to handle and less fatiguing during longer sessions. For typical turf grasses, it’s exactly the kind of controlled cut you want.

Line feed and the spool system

The automatic feed spool (AFS) is a big part of this trimmer’s appeal. There’s no bumping; the head meters out line as needed. Most of the time, it works seamlessly—you stop and restart, and the line is at the right length. Every once in a while, especially with lots of stop‑start trimming around obstacles, it will feed a tad more line than I need, and you hear the guard’s blade trim it back. That’s normal behavior for auto‑feed systems but does use line a bit faster than a bump‑feed head in experienced hands.

A few practical pointers from use:
- Keep a spare AF‑100 spool on hand. Swapping takes seconds and doesn’t require tools.
- If you wind your own spools, stick with quality 0.065 line and wind tightly and evenly to avoid feed hiccups.
- Clean out grass fines that can pack around the head after dusty sessions; it helps the feed system stay consistent.

Edging mode in the real world

The head rotates for vertical edging, and there’s a flip‑down guide to help keep lines straight. For short stretches around beds and along walkways, the edging function is genuinely handy—no need to pull out a separate tool. However, because there isn’t a dedicated guide wheel, holding a crisp vertical line for long runs takes practice and forearm endurance. I treat the edging mode as a convenience feature for touch‑ups rather than a full replacement for a wheeled edger on long sidewalks.

Ergonomics, balance, and noise

At roughly 6.5 pounds without the battery, the trimmer feels nimble. The auxiliary handle adjusts quickly, and the shaft length accommodates different heights, so I could dial in a comfortable stance whether I was trimming under shrubs or reaching along fence lines. Vibration is modest—far less fatiguing than a small gas unit—and the trigger response is smooth.

Noise-wise, it’s not whisper‑quiet. The high‑pitched whir carries, especially at higher power settings, so I still wear hearing protection. It’s a different sound profile than a 2‑stroke—less rumble, more whine—but don’t expect late‑night stealth trimming.

Battery life and charging

Runtime depends heavily on the power dial and the density of what you’re cutting. With a typical 40V pack, here’s what I’ve consistently seen:
- Mid power: roughly 20–30 minutes of continuous trimming, enough for a small to midsize yard.
- High power: closer to 12–18 minutes when pushing through thicker areas.

The upside of the dial is control—you can manage your battery like a fuel tank, saving the top settings for tough spots and cruising on lower settings elsewhere. For larger properties or if you like to edge and trim in one session, a second battery makes the experience much smoother.

Build quality and maintenance

Construction leans heavily on durable plastics, but nothing feels flimsy. The guard is rigid, the shaft locks positively, and the trigger has a reassuring pull. Maintenance is minimal: keep the head clean, swap line when needed, and wipe down the guard.

Other observations:
- The line cutter in the guard is sharp and keeps the cutting length consistent.
- The motor housing sheds debris well; I didn’t notice heat issues even in warm weather with normal duty cycles.
- Because it’s electric, there’s no fuel storage, mixing, or carb issues to fuss with—one of the biggest reasons I reach for it first.

Where it shines—and where it doesn’t

Best for:
- Homeowners managing small to medium lawns who want a low‑maintenance, easy‑handling trimmer.
- Weekly maintenance trimming and light edging around beds, walkways, and fences.
- Users already on the Black+Decker 40V MAX battery platform.

Not ideal for:
- Overgrown lots, thick brush, or heavy weed clearing. A dual‑line head or a more powerful platform (or gas) will be faster.
- Long, precise edging runs if you’re particular about dead‑straight lines; a wheeled edger is better for that.

Tips for better results

• Match the power dial to the task. Lower settings keep lawns tidy while preserving battery; only punch up for tough patches.
• Keep spare line on hand. Auto‑feed is convenient but plan for a bit more line use than bump‑feed systems.
• Use fresh, high‑quality 0.065 line to keep feeds smooth and reduce breakage.
• Wear eye and hearing protection. Electric is cleaner and lower vibration, but debris and noise are still real.

The bottom line

The 40V Black+Decker trimmer hits a practical sweet spot for homeowners: light, simple, and capable enough to keep typical lawns looking sharp with minimal fuss. The power dial gives it range, the automatic feed keeps things moving, and the overall ergonomics make it easy to use for a full session without sore forearms. It’s not a brush‑clearing beast, and the edging mode functions best as a convenience feature rather than a pro‑level edging solution, but that’s a fair trade for the weight, ease of use, and low maintenance.

Recommendation: I recommend this trimmer to homeowners who want a reliable, hassle‑free tool for routine lawn trimming and occasional edge touch‑ups, especially if you’re already invested in Black+Decker’s 40V batteries. If your yard regularly throws dense weeds or you demand long, crisp edging lines, look to a more powerful dual‑line unit or a dedicated edger. For everyday trimming chores, this 40V model is an easy tool to live with and one I reach for first.