DeWalt 20V MAX Lithium-Ion 4.0Ah Battery (2-Pack)

Why I reached for these 4.0Ah compacts

I swapped my go-to 2.0Ah packs for these 4.0Ah compact batteries to see if I could squeeze more runtime out of my 20V MAX tools without adding much bulk. Over a few weeks on site and in the shop—driving structural screws, trimming plywood, and running an oscillating tool for punch-list work—the two-pack consistently gave me the “extra hour” feeling I was hoping for, while still keeping tools light and nimble.

These are compact 4.0Ah packs (about 80 Wh each) with a 3‑LED fuel gauge. They’re sold as a two-battery set and don’t include a charger. In short, they aim to bridge the gap between the featherweight 2.0/3.0Ah compacts and the bulkier 5.0Ah bricks. In practice, they largely nail that brief.

Size, balance, and handling

On paper, each pack weighs about 1.15 lb, and in the hand they feel close to a typical 3.0Ah compact—just a touch wider. That wider base isn’t a bad thing: drills and drivers stand more securely on flat surfaces, which I appreciated on uneven subfloor. The height remains compact enough that I could still fit a drill/driver into cabinet boxes and between studs where a 5.0Ah would feel crowded.

Balance is where these shine. On an impact driver and compact drill, the center of gravity stays close to the grip, reducing wrist fatigue overhead. Compared with a standard 5.0Ah, I noticed less forearm burn at the end of a long day installing cabinet hardware. On heavier tools—circular saw, recip saw—the smaller footprint doesn’t transform the tool, but it keeps things from getting tail-heavy.

Runtime and performance

Runtime gains over 2.0Ah and 3.0Ah packs are real and noticeable. In mixed use:

• Driving 3-inch construction screws into SPF, I averaged around 35–40% more fasteners per charge compared with a 3.0Ah compact, and roughly double a 2.0Ah.
• With a 6-1/2 inch circular saw breaking down 3/4 inch plywood, I got several more rips per charge versus a 3.0Ah—not enough to replace a 5.0Ah for heavy cutting days, but enough to finish a set of cuts without a mid-task swap.
• On my oscillating tool (which can be a battery hog), the extra capacity translated into fewer hot-swaps and a smoother cadence on punch lists.

Power delivery stayed consistent through most of the charge. Voltage sag under heavy load felt similar to other quality compacts: the pack doesn’t make your tools stronger, it just keeps them running longer before tapering near the end. Thermal management was solid; even after sustained cuts, the packs got warm but not so hot that the charger refused to start.

If you live on grinders, a recip saw in demolition, or all-day circular saw use, I’d still point you to a 5.0Ah (or higher) pack. For drilling, driving, finish cutting, assembly, service work, and trim carpentry, these 4.0Ah compacts hit a sweet spot.

Charging and battery management

With a standard 20V MAX charger, I averaged around 45 minutes from empty to full, matching the spec. On a fast charger, that dropped a bit, but not dramatically—heat is the limiting factor more than charge electronics. The 3‑LED fuel gauge is easy to see and reasonably accurate, though with only three steps it’s coarse; I generally treat two bars as “finish this task and swap soon.”

Self-discharge was negligible over a couple weeks on the shelf. In cold weather (mid‑30s °F), I saw the expected dip in runtime—nothing abnormal for lithium-ion. Keeping the packs warm in a jacket pocket or cab before use helped.

Fit and compatibility

These packs work across the 20V MAX ecosystem, and I ran them on drills, impacts, an oscillating tool, and compact saws without electrical compatibility issues. Mechanically, the fit was snug on a few older tools and one of my chargers. The rails felt tight for the first several insertions; after a week, they loosened to a comfortable, secure fit. If you experience stickiness:

• Check for debris on the battery rails and tool shoe; a quick brush or blast of compressed air helps.
• Avoid lubricants; a plastic-safe dry lube used sparingly can help, but oil attracts dust.
• Seat and release in a straight line—angling increases friction on snug rails.

Once broken in, I preferred the firm lock-up to the slight wiggle I get from some older, heavily used compacts.

Build quality and durability

The housings feel robust with clean molding and a dense, solid core. The wider base gives them a planted stance when standing tools upright. I dropped one from bench height onto plywood; it scuffed but kept working fine. The LED gauge buttons are positive without being proud, so accidental presses in a bag are rare.

As with most compact packs, there’s limited rubber overmold—these aren’t armored like some high-capacity packs—so I wouldn’t use them as shop-floor skates. That said, the build inspires confidence for daily use. The warranty coverage (three-year limited, one-year service) and a 90-day return window are in line with expectations for this class.

Value and where they fit in the lineup

As a two-pack, the value is good if you’re already invested in 20V MAX and want to upgrade older 2.0Ah/3.0Ah packs. You’re paying for capacity and compactness, not raw peak output. Compared with a single 5.0Ah, two compact 4.0Ah packs let you keep one on the charger and one on the tool, which kept my workflow smooth. If you need sustained heavy-load cutting or grinding, a 5.0Ah or higher-capacity option may still be a better primary battery, with these as your light-duty/overhead companions.

If you’re considering ultra-compact options for fastest handling, the smallest packs still win on size and weight, but you’ll swap more often. On the other end, newer high-output or advanced cell packs offer better heavy-load performance but add cost and mass. These 4.0Ah compacts sit comfortably in the pragmatic middle.

Quirks and trade-offs

• Fit can be tight on some tools and chargers until the rails break in.
• The 3‑LED gauge is coarse; more steps would be helpful for planning.
• Not the best choice for grinders or demo recip saws under continuous heavy load.
• Charger isn’t included—fine for most, but worth noting if this is your first set.

None of these are deal-breakers, but they’re good to know before you buy.

Who benefits most

• Trades that prioritize overhead or one-handed work: electricians, HVAC techs, cabinet installers, maintenance crews.
• DIYers and pros tackling mixed tasks where tool agility matters as much as runtime.
• Anyone standardizing on compact batteries for drills/drivers while keeping a few larger packs for saws.

The bottom line

These 4.0Ah compact batteries find a practical balance: meaningfully more runtime than 2.0/3.0Ah compacts, with only a small bump in size and weight, and far better maneuverability than full-size 5.0Ah packs. They charge in a predictable window, run cool under normal loads, and lock solidly onto tools—tight at first, then reassuring.

Recommendation: I recommend this two-pack to anyone in the 20V MAX ecosystem who wants longer runtime without turning their drill or impact into a tail-heavy brick. They’re a smart daily-driver battery for light-to-medium tasks, service work, and trim. If your work leans heavily on grinders or continuous saw use, pair these with a higher-capacity pack for the heavy lifting. For everyone else, these compacts hit a very practical sweet spot.