Which is better for a circular saw?

The DCB2108 8Ah. A saw pulls hard, and the 8Ah roughly doubles runtime before a swap. The 4Ah is fine for short cuts but will send you to the charger sooner.

Which is better for a drill or impact driver?

The DCB2104 4Ah for most drilling and driving. The lighter pack keeps the tool balanced, and 4Ah is plenty for typical jobs. Step up to the 8Ah only if you drive long runs of screws all day.

Is the 8Ah worth the extra money?

Yes if runtime is your problem. At $129.90 to $130.00 versus $51.99 to $63.70, you pay about double for about double the capacity, so the value per amp-hour is similar.

Do both fit the same tools and chargers?

Yes. Both are 20V MAX packs and work with 20V MAX tools and chargers. Neither listing includes a charger.

Both use tabless cell technology, which DeWalt aims at longer cycle life. The 8Ah should run longer per charge; the 4Ah is under less stress per cell at the same draw, but DeWalt gives no cycle count for either.

How heavy is the 8Ah?

2.2 lb for the battery alone. DeWalt does not list a weight for the 4Ah, but a 4Ah pack is noticeably lighter on a drill or when working overhead.

DEWALT 20V MAX Battery XR POWERPACK 4Ah Lithium Ion Battery (DCB2104) vs DeWalt DCB2108 20V MAX XR POWERPACK 8 Ah Battery

Buy the DCB2104 4Ah if you want a lighter, cheaper pack for drills, drivers and saws used in short bursts. Buy the DCB2108 8Ah if runtime is the bottleneck: it roughly doubles capacity and adds weight. The 4Ah has ranged from $51.99 to $63.70 since October 29, 2026; the 8Ah has held near $129.90 to $130.00 since October 30, 2026, so the 8Ah costs about twice as much for about twice the capacity.

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