Black & Decker 12 inch 3-in-1 Compact Mower

Why I picked it up

I bought the 3-in-1 compact mower to tame a small backyard that’s awkward to reach and too tight for a full-size mower. The promise of one tool that mows, trims, and edges—powered by lightweight 20V batteries—was appealing. After several cut cycles on both tidy lawn and neglected, weedy patches, I have a good sense of where this compact machine shines and where it falls short.

Setup and design

Out of the box, assembly is straightforward. The trimmer snaps into a small mower deck, the auxiliary handle and guard bolt on, and the two 20V MAX lithium-ion batteries charge on a wall-mountable base. The tool is light (around 15 pounds with the deck), and the footprint is tiny. It stores in a closet or hangs easily in a garage without dominating your space.

Switching modes is the headline feature. Push a latch, lift the trimmer out of the deck, and it becomes a standalone string trimmer. Rotate the trimmer head and it becomes an edger. The conversion is quick and intuitive, so you can mow the open areas, pop out to trim around obstacles, then edge along beds and walkways without hunting for another tool.

The deck height and trimmer length are adjustable, and the handle pivots to help you reach under shrubs or along slopes. The auto-feed line system (AFS) advances string without bumping, which keeps the workflow smooth.

Mowing performance

If you’re imagining a standard blade spinning inside a deck, reset expectations. This is a trimmer mounted on a compact, wheeled deck. It cuts a 12-inch path and, surprisingly, it can produce an even-looking finish on small lawns when you keep up with maintenance. In short, it feels a lot like vacuuming your yard. Push forward, overlap your passes, and it leaves a consistent cut.

In regularly maintained grass, the transmission keeps the head from bogging, and I could move at a steady walking pace. Where it slows down is in thick, tall, or dense varieties (think weeks of growth or tough warm-season grass). There, I had to make multiple passes, raise the deck height, or skim the top first and then lower it for a second pass. Wet clippings or long strands can accumulate inside the guard; a quick scrape-out mid-session restores airflow and cutting efficiency.

Pros as a mower:
- Compact, goes places bulky decks can’t
- Surprisingly even cut on small, flat patches
- Easy to guide under low branches and around landscaping

Cons as a mower:
- Slower in dense or overgrown areas
- Narrow 12-inch swath means more passes
- Clippings can build up in the guard if you let grass get long

Trimming and edging

As a standalone trimmer, it’s nimble and light. The auto-feed spool takes care of line advancement, and I didn’t have to bump the head. The trade-off is line consumption: edging eats line faster than trimming. Keep an extra spool on hand (one AF-100 is included), especially if you edge regularly.

Edging results are clean enough for patios and sidewalks once you get your pace right. The wheel on the mower deck isn’t used in edger mode, so you guide the tool by hand; a slow, steady pass delivers the best line and finish.

Pros for trim/edge:
- Quick conversion between modes
- AFS keeps the cut going without interruption
- Good control for fence lines, posts, and beds

Cons for trim/edge:
- Uses line faster when edging
- Takes a light touch to keep edges straight until you find your rhythm

Battery life and charging

Runtime is the most important limiter here. The kit includes two 20V 2.0Ah batteries (one required to run). In average-height grass, I typically get roughly 20–25 minutes per pack, sometimes a bit less if I’m doing heavy edging or chewing through thicker growth. That means the pair gives me about 40–45 minutes of mixed work on a good day.

Charging takes time: about four hours per battery on the included base. If you plan to do front and back lawns in one session, you’ll want both batteries topped off. For larger tasks, either pace the work over two days or consider adding a higher-capacity 20V battery to your kit.

What works well:
- Two batteries in the box, so you can swap mid-session
- Lightweight packs keep the tool balanced and easy to handle

What could be better:
- Long charge time on the standard charger
- Runtime can feel tight if you’re tackling both overgrowth and edging in one go

Ergonomics and user comfort

The overall balance is good, and the pivoting handle helps when trimming along slopes or reaching under bushes. The tool’s small diameter grip fits smaller hands comfortably. Holding the trigger continuously, though, can be fatiguing during longer sessions; a trigger lock would go a long way here.

Height-wise, the trimmer shaft extends, but taller users may still want more length. I’m on the taller side and found myself wishing for another inch or two to stand fully upright while trimming. The mower deck rides a bit ahead of you, which is great for reach but can make the handle feel short.

Noise is considerably lower than a gas mower and on par with a robust string trimmer. Vibration is modest.

Maintenance and durability

There’s not much to fuss over. The string spool is the consumable. If you mow regularly and edge every session, you’ll go through more line than you might expect—normal for auto-feed systems. Keep an extra AF-100 on the shelf and you’re covered.

The detachable deck is mostly plastic, which keeps weight down but also means the latch and fit are critical. Mine locks in, but there’s a bit of play if you rock it aggressively. I added a simple strap around the neck of the trimmer and deck to remove any wiggle when mowing bumpy areas—an easy, reversible hack. After regular use, the mechanism still works, but it’s an area to treat with a little care.

Cleaning is fast: pop the trimmer out, brush off clippings, and check the guard for buildup. The motor housing is sealed enough for yard work, and the 2-year limited warranty offers some peace of mind.

Limitations to keep in mind

• It’s not a replacement for a full-size mower on medium or large lawns.
• Dense, wiry grass requires patience and multiple passes.
• Battery runtime demands planning; the charge cycle is slow.
• Taller users may find the shaft length borderline for long trimming sessions.

None of these are deal-breakers for the right yard, but they define the use case.

Who it’s for

• Small urban or suburban lawns where maneuverability matters more than speed
• Townhome or duplex yards with obstacles, beds, and tight access
• Homeowners who want one lightweight tool to mow, trim, and edge without mixing gas or storing a big machine
• Anyone who prefers quiet, low-maintenance yard work and doesn’t mind working in shorter bursts

Who should look elsewhere:
- Owners of thick, fast-growing lawns or large lots
- Users who need long, uninterrupted runtime without investing in extra batteries
- Folks who prefer a metal-deck, blade-style mower finish above all else

Recommendation

I recommend the 3-in-1 compact mower for small yards and spotty access areas where a full-size mower is overkill. It earns its keep with quick mode changes, easy maneuverability, and clean-enough results across mowing, trimming, and edging. Plan around the battery window—about 40–45 minutes with the two included packs—and be prepared to mow more frequently to avoid multi-pass sessions in overgrowth. If you’d like more runway, add a higher-capacity 20V battery and keep an extra line spool on hand.

For compact spaces, minimal storage, and light-to-moderate grass, it’s a practical, low-hassle solution that turns yard work into a set of short, manageable tasks. If your lawn is larger or especially dense, a wider-deck mower or a more powerful system will be a better fit.