Review: Dark Energy’s Reservoir – 8000 mAh Portable Charger

by Khalid Hosein on November 3, 2013

Reservoir portable USB chargerAnother portable charger you say? But wait, you’ll want to read about this one. The $129 Reservoir from Dark Energy is an 8000 mAh monster that can do double duty charging either 2 phones at once or 1 phone and 1 tablet.

I love the design – the all black, rubberized look with the pattern of indented circles immediately reminded me of the monolith slab from the book/movie 2001: A Space Odyssey. It does also come in white, and it would be nice to see other colors in the future. Unfortunately, the first photograph doesn’t do it justice. Take a look at the one below.

I was really surprised and happy about the weight. I completely expected it to be a great deal heavier given its capacity. I have another portable charger that could recharge my 2300mAh phone about 1.5 times that is at least as heavy as the Reservoir. Obviously, material choices make quite a difference.

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Size: not much larger than many slab phones today, and not much thicker. It would fit nicely into a pocket inside a typical carrying/laptop bag, backpack, briefcase, or even your pants pocket. Take a look at the 2nd photo to see its dimensions.

The Reservoir  has 2 USB power ports, one designed for phones and the other for tablets or larger devices. While it can charge your phone and tablet or 2 phones simultaneously, it is not designed for charging 2 tablets at once. Oh, there is one feature that I have not seen myself on another charger, and that’s a power button. It doubles as a toggle to start/stop the flow of juice to your device in need of power, and when it’s not charging as a way to light up the LEDs to let you know how much charge it still has.

Reservoir portable USB charger

Now let’s talk about what it can really do: (re)charging. If you look at the Dark Energy website, they claim that the Reservoir can charge a typical smartphone 3-6 times. That’s quite a range. 6 times would mean that smartphone would only have about a 1300-1400 mAh sized battery, but this is still a reality with some older phones out there on the market, so 6x is not really a reach. So yes, the claim that the Reservoir can charge  a phone for a week is also not a shot in the dark. Of course, you’ll need to do your homework to understand what you’re really getting for the hardware you already have.

In my case, I tested the Reservoir with my 2300 mAh smartphone and found that yes, it did charge it just fine 3 times and had room to spare. Now, this was not a scientific test. But then neither will your usage be. I didn’t run my battery down to absolutely nothing before hooking it to the Reservoir, and neither will you. What you need to know here is roughly what sort of performance you’ll get.

If I got a Galaxy Note 3 with its 3200 mAh battery, then I’m only going to get about 2.5 charges out of the Reservoir, but considering how long 3200 mAh is going to take me, it’s a fair trade-off.

Another nice thing about the Reservoir is that it is well-designed in the power transfer department. I’ve had other cheap(er) chargers that would throw off so much heat in the process that you couldn’t hold onto them for very long. The Reservoir on the other hand doesn’t appear to change temperature at all.

It does take a good 4-6 hours to recharge this 8000 mAh behemoth, but that’s only if you drain it all the way down. The better approach is to just top it off frequently, so you have its full tank ready to go when you really need it.

Things I would change/tweak:

  • Instead of only 3 blue LED lights to indicate how much charge is left in the battery, I would go to at least 5 lights. Better yet, a small embedded digital display that shows the numerical percentage left.
  • The USB outlets have small very lightly colored icons indicating that one is for phones and the other for tablets/larger devices, but in certain light, they are really hard to make out. Of course, after some time using the Reservoir, you’ll know which one is which, but why guess or need to memorize? I get that it’s part of the design, but a smartly chosen color – say matching that of the blue LEDs – would take nothing away from its looks and add to its utility.

These are but minor cosmetic items, and don’t affect my overall opinion of this product. If you find yourself with a dead phone on a regular basis, I highly recommend the Reservoir. It’s lightweight, and thin enough to fit in many carrying cases. And with its large capacity, you don’t need to worry about recharging it daily. This is without a doubt its greatest differentiator in the portable charger market. The Reservoir has now made it to the top of my list of portable chargers.

(Disclaimer: Gizmos for Geeks received a complimentary review copy of this product, many thanks to Dark Energy.)

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