Thinking about buying a hybrid PC that runs full Windows? Well, then battery life had better be on your radar, or you might end up with a device that conks out after just a few hours. If you own a Microsoft Surface, then that's becoming less of an issue. We've been testing a new accessory that can make a big difference in extending its uptimes. Read on, as Gizmag reviews the Surface Power Cover.

Microsoft says that the Power Cover can extend Surfaces' battery life by "up to 70 percent." It plays nicely with all four Surfaces: the Windows RT-running Surface RT and Surface 2, and the full Windows-running Surface Pro and Surface Pro 2.

If you've seen Microsoft's Type Cover 2 for Surface, then you already have a pretty good idea of what you're getting from the Power Cover. This is basically a thicker and heavier version of the Type Cover 2, only with a built-in battery. It also doesn't have the Type Cover 2's backlit keys. That's probably because they use extra power, which would kinda defeat the whole purpose.

I had been using the Type Cover 2 for a couple of weeks before switching to the Power Cover, and when I picked this sucker up, I really noticed a difference. This is a pretty damn heavy keyboard cover. At 535 g (1.18 lb), it's actually 110 percent heavier than the Type Cover 2. It's also 90 percent thicker.

That part doesn't bother me though. Lightness isn't exactly the Surface Pros' forte to begin with, so what's a little extra heft? When I feel that weight, I just remind myself how much extra juice I'm getting out of the deal. As far as I'm concerned, it's a small price to pay for all-day battery life.

On lap, I think that extra weight is actually an advantage. The Type Cover 2 is firmer than the somewhat-flimsy Type Cover 1, but the Power Cover takes it to another level. It's a firmer foundation, and much closer to the feeling of using a standard laptop.

And yes, the Power Cover does make a big difference with battery life. Using the Pro 2 with the Type Cover 2, I can usually make it through a good portion of the day without charging. But if I'm doing a lot of Photoshopping, I still have to juice it up on breaks or things might get tight. With the Power Cover attached, I don't have to pay much attention to battery life at all. Even on days when I spent a few hours in Photoshop, the Pro 2 lasted throughout the workday. For a full-blown PC, that's a pretty big deal.

I did a more formal test too, streaming Netflix over Wi-Fi with brightness set at 75 percent. There the Pro 2 saw about a 33 percent increase with the Power Cover attached. On the original Surface Pro, which has much shorter battery life, the Power Cover gave it about a 67 percent boost. I'm not sure if video tests are the best way to test a full-blown PC's battery life, as there are a lot more background processes running than on mobile devices like the iPad. But you get the picture: the Power Cover can give the original Pro respectable uptimes, and it can turn the Pro 2 into an all-day machine – even under pretty heavy use.

How does it work? Well, when you look at Windows' battery life popup, you see Battery #1 (your Surface) and Battery #2 (the Power Cover). The Surface uses the Power Cover's juice first. Only when the Power Cover is drained (or detached) does it start using the Surface's internal battery.

When you're charging, the inverse is true. It powers up the Surface first, then after it reaches 80 percent full, it juices up the Power Cover. After the Power Cover reaches 80 percent, it finishes charging the Surface. Then it finishes charging the Cover.

The Power Cover ain't cheap, at US$200. And when you're looking at the Surface Pro 2, which starts at $900 and moves all the way up to $1,800, things are starting to get pretty damn expensive. But if you spend any time doing things like Photoshopping, video-editing, or gaming, then you might find that it's worth it. It's "only" $70 more than the Type Cover 2, and I think it gives you more bang for your buck. Apart from the missing backlit keys, it's just as good of a keyboard, with a firmer base, and hours of extra battery life.

And if you own the original Surface Pro, the Power Cover can breathe new life into your PC. From my experience, I'd say its uptimes with the Power Cover should be pretty close to those of the Surface Pro 2 without the Power Cover. If you were trying to avoid upgrading to the second-gen model, then this $200 accessory might be just what the doctor ordered.

Gizmag highly recommends the Power Cover for any Surface Pro or Pro 2 owner looking to eke out a few extra hours of battery life. If you own the Surface RT or Surface 2, your battery life is probably already good enough without it. The Power Cover is available now from the product page below.

For more on the latest Surfaces, you can check out Gizmag's reviews of the Surface 2 and Surface Pro 2.

Product page: Microsoft

Edited on April 26 to more accurately describe the charging process