If you grew up with a Nerf Bow 'n' Arrow, you might not recognize foam warfare today. These days, you can buy a fully automatic Nerf machine gun that rains down darts from dual drum magazines -- or soon, a 100-round cannon that fires foam balls at 70 mph.

But there is one thing you probably would be familiar with: the ridiculously heavy, underpowered, century-old C- and D-cell alkaline batteries that are holding the sport back.

The biggest leap forward for foam warfare since magazine-fed blasters.

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Enter the Nerf Rival Rechargeable Battery Pack -- a nickel-metal hydride (NiMH) pack that not only improves the rate of fire of a Nerf blaster, but weighs roughly a quarter of the six D-cell batteries it replaces.

When I first heard of the battery, I was skeptical. How much better could it be? So I stuck six brand-new D-cell batteries and one fully charged Rival Rechargeable Battery into the fully auto Nerf Rival Khaos blaster for a side-by-side test.

The difference was stunning. With the rechargeable pack, the blaster shot faster (7 rounds per second versus 5 rounds per second), harder and -- importantly -- spun up the motors more quickly. That way, when you spot a foe, you get the first shot off faster. (See for yourself in our video at the top of this post.)

For years, serious Nerf fans have ripped apart their blasters, replaced the motors, resoldered connections and added their own rechargeable batteries to get these kinds of results. Now, it's in a $30 package you can buy right off the shelf. (It's not yet out in the UK or Australia, but that converts to roughly £25 or AU$40.)

Josh Miller/CNET

As of right now, we're only aware of two blasters that use the battery pack (the Rival Khaos, and the upcoming Rival Nemesis), and we're not yet sure how the battery will last over the long haul. We can't yet say how many times you can recharge it, for example, before it loses some of its oomph.

But compared to ancient D-cell alkaline battery technology, it's already pretty clear: If your blaster is compatible, this pack is a no-brainer. I'll be buying one myself.

The upcoming Nerf Rival Nemesis, with its 100-round capacity, will also be compatible with the battery pack.

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