DeWalt 20V MAX 4Ah Battery

A battery can make or break a cordless setup, and over the last few months I’ve been swapping this 4Ah compact onto everything from an impact driver to a 20V ratchet. It hits an appealing middle ground: meaningfully longer runtime than the 2Ah compact packs without the bulk and nose-heaviness of a 5Ah or larger brick. In day-to-day work, that balance matters more than spec sheets suggest.

Build and ergonomics

Physically, the pack stays in the “compact” footprint, which keeps small tools nimble. On a drill/driver or impact driver, it keeps the handle-to-head balance right where I want it—enough mass to steady the tool, not so much that it feels clubby. On an oscillating tool and 20V ratchet, the difference versus a 5Ah pack is huge; you can get into tighter spaces and hold awkward angles longer.

Weight is about 18.4 oz (1.15 lb) on my scale. The housing is typical DeWalt: rigid shell, solid latches, tight fit at the rails. The three-LED fuel gauge is easy to thumb—no hunting for a tiny button. I’d still prefer a five-bar gauge for finer granularity, but the three-step indicator is consistent pack to pack.

Internally, this is a compact 4Ah design using 18650 cells rather than the larger 21700 format found in some high-output DeWalt packs. That’s how it stays small and light. The trade-off is absolute current delivery and thermal headroom, which I’ll get to in the performance section. The short version: it’s plenty for most carpentry, electrical, plumbing, and mechanical tasks, and only shows limits on the hungriest tools.

Runtime and power in use

On runtime, the pack delivers what its 80 Wh rating promises. Some real-world examples from my notes:

• Framing/trim: With an XR impact driver driving 3-in deck screws into SPF, I averaged just under 300 screws on a charge. That’s a mix of single and double laminations, intermittent use over a few hours. A 2Ah compact gets me roughly half that; a 5Ah pack gets about 35–40% more but with more weight.
• Drilling: With a brushless drill and a sharp 1-in spade bit into studs, I got 45–50 holes before the pack hit the last bar and voltage sag became noticeable. With 1/2-in auger bits, the count increases substantially; I didn’t run it to empty, but 80+ holes wasn’t a problem.
• Oscillating tool: Flush-cutting door jambs, trimming shims, and some grout removal, I got about 90 minutes of actual trigger time. The pack warmed but never thermalled out.
• Lighting/low-draw: On a compact area light at a modest brightness setting, I got a hair over 7 hours. This is where 4Ah shines—plenty of runtime, minimal bulk if you’re carrying it around all day.

Power delivery is stable. On high-draw tools—compact circular saws, small angle grinders, or recip saws—the pack will run them, and for quick cuts it’s perfectly fine. If you’re ripping long sections of 3/4-in sheet goods, chewing through nail-embedded lumber, or grinding aggressively, you’ll want a larger-capacity, higher-output pack (think 5Ah/6Ah/8Ah with 21700 cells). The 4Ah compact is designed to be the go-to for most hand tools, not the hero battery for continuous heavy load.

Cold-weather behavior aligns with what I expect from modern lithium-ion. At around 30°F, I saw roughly a 15–20% runtime penalty and a bit more voltage sag under heavy load. It still got the work done, but I let the pack warm up before recharging to avoid the charger’s cold pack delay.

Charging and battery management

Charging on a standard 20V MAX charger takes about 45 minutes from one bar to full in my shop conditions. That’s fast enough that with two packs in rotation, I never hit downtime on typical tasks. If you run a fast charger, you can shave that further, but the standard rate is gentle on the cells and better for longevity.

The fuel gauge is accurate and repeatable. Two bars really does mean “keep going without worry,” while one bar tells me to plan a swap soon. The pack won’t jump on the charger if it’s hot from continuous use; it waits to cool, then starts. That’s smart protection and, after a few cycles, becomes a non-issue in workflow.

One practical tip: check the date code when you get new packs. Lithium-ion ages slowly in storage, but I prefer packs manufactured within the last year if I’m building out a kit. Mine arrived clean, sealed, and at a safe storage voltage.

Compatibility and use cases

Compatibility is straightforward: it’s at home on the full 20V MAX line and charges on the standard 20V MAX chargers. It’s not a FlexVolt pack, so it won’t run 60V tools (and doesn’t try to). Where it shines:

• Everyday drivers and drills, especially compact brushless models
• Oscillating multi-tools and 20V ratchets
• Compact recip saws for one-off cuts
• Jobsite lights, inflators, and radios where size matters
• Service work and punch lists where you value light weight and quick swaps

Where I prefer something bigger: grinders, circular saws on long rips, and continuous recip saw demolition. The 4Ah compact will do these jobs, but you’ll notice faster depletion and more heat buildup. That’s not a flaw—just the reality of matching the pack to the task.

Durability and warranty

I’ve cycled this pack dozens of times now. The latches still snap crisply, the rails show minor scuffing as expected, and there’s no rattle or case flex. DeWalt’s electronics have been conservative about charge and discharge; I haven’t experienced shutdowns except when pushing a compact circular saw through dense material for an extended cut, at which point the pack took a brief cool-down before recharging normally.

The support terms are generous for a battery: a 3-year limited warranty, one year of free service, and a 90-day satisfaction guarantee. Batteries are consumables, but that coverage shows up when a pack exhibits early defects—exactly the edge cases you want covered.

What I’d change

• Finer gauge resolution: Three LEDs are fine, but five would make planning swaps easier.
• Grip/footing: A thin overmold or rubberized base would help the pack stay put on smooth surfaces and soften the blow when it’s set down on finished flooring.
• Include a protective terminal cap in the box. It’s a small piece of plastic that goes a long way in the bag or toolbox.

Those are nitpicks more than dealbreakers, but they’re the sort of small improvements that add up over a fleet of packs.

Alternatives and positioning

This 4Ah compact sits in a sweet spot:

• Versus 2Ah: roughly double the runtime with a nearly identical footprint and only a modest weight bump. If you’ve been living on 2Ah packs, this is a tangible quality-of-life upgrade.
• Versus 5Ah/6Ah: less runtime and peak output, but it’s lighter and less cumbersome. For grinders, circular saws, or all-day cutting, the bigger packs still earn their keep.
• Versus 8Ah (and other 21700-based packs): the big packs offer serious current and runtime, but at a real size/weight penalty. I reserve them for high-draw tools and production runs.

For most trades and homeowners with a mix of 20V tools, the 4Ah compact is the one you’ll grab first and miss when it’s not in the bag.

Recommendation

I recommend the DeWalt 4Ah compact battery as the default pack for the 20V MAX platform if you value a strong runtime-to-weight ratio. It meaningfully extends runtime over 2Ah compacts, keeps tools balanced and maneuverable, and charges quickly enough that two packs will cover continuous work. It pairs especially well with drivers, drills, oscillating tools, ratchets, and jobsite accessories, and it’s perfectly serviceable for occasional use on saws and grinders.

If your day is dominated by high-draw cutting and grinding, step up to a 5Ah/6Ah/8Ah pack for more headroom. Otherwise, this 4Ah compact hits the sweet spot and has become my first-choice battery for most 20V tasks.