1 used from $39.99

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uNu Power DX External Protective Battery Case for iPhone 4S & 4 - MFI Apple Certified (Matte Black, Fit All Models iPhone 4 & 4S)

by UNU
3.6 out of 5 stars 1,728 customer reviews
| 73 answered questions

Available from these sellers.
Standard Packaging
  • Highlighted by its lightweight, ultra slim design, the DX case measures an impressive thickness of just 17mm. Featuring the strengthened polycarbonate housing, raised lips around front screen, and form fitting design, the DX will provide the most comprehensive protection to your iPhone 4/4S.
  • Awarded the prestigious Made for iPhone certification, the DX has gone through extensive testing and quality assurance to ensure reliability. In fact the DX has been proven to give quality power even after 500 full recharging cycles!
  • Made with state-of-the-art technology, the DX allows users to use any function button with case one, sync and charge with the case equipped, and visualize current battery levels (of the case) via the sky-blue 4-LED battery level indicator.
  • The DX case is backed by the 1 Year worry Free Warranty with Coverage on any factory defects. It also comes with free Gifts including: 1 x High Quality Screen protector, 1 x Micro Fiber Cleaning Clothe, 1 x USB charge & sync cable.
  • Equipped with a 1700mAh battery cell the DX almost doubles the life of an iPhone 4/4s. The additional power yields six hours of talk-time, 30 hours of music playback, and a hefty 240 hours of standby time.
1 used from $39.99

High-Quality Portable Power Banks from AmazonBasics
16,100 mAh
16,100 mAh $29.99
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10,000 mAh $24.99
5,600 mAh
5,600 mAh $19.99
3,000 mAh - Ultra-Thin
3,000 mAh - Ultra-Thin $5.99 - $29.99
2,000 mAh - Ultra-Thin
2,000 mAh - Ultra-Thin $5.99

Technical Details

Color: Black | Product Packaging: Standard Packaging
  • Size (LWH): 0.75 inches, 2.5 inches, 5 inches
  • Weight: 2.56 ounces
  • Minimum Rated Talk Time: 10 hours
  • Minimum Rated Standby Time: 210 hours
  • Battery Type: Lithium Polymer
  See more technical details

Product Description

Color: Black | Product Packaging: Standard Packaging

Our Amazon's best-selling battery case for iPhone 4/4s, the DX battery case boasts a thickness of just 17mm, while also effectively doubling battery life. This technically advanced case also halves the time needed to re-charge the battery. It even allows users to sync-and-charge while the case is still attached to the iPhone. Also, made for complete protection, the DX exhibits an ergonomic hand-held fit, an anti-slip coating, and a comprehensive casing to ensure peace-of-mind.


Battery Material: Lithium Polymer
Battery Capacity: 1700mAh / 3.7V
Dimension 120x62x17 (mm)
Charging Time 3-4 hours
Life Cycles >500 Cycles

Box Content

1 x DX 4 iPhone 4/4S Battery Case
1 x Data Charging USB Cable
1 x User Manual
1 x Crystal Clear Screen Protector
1 x Microfiber Cleaning Clothes

Product Details

Color: Black | Package Type: Standard Packaging
  • Product Dimensions: 0.8 x 2.5 x 5 inches ; 2.6 ounces
  • Shipping Weight: 4 ounces
  • Domestic Shipping: Item can be shipped within U.S.
  • International Shipping: This item is not eligible for international shipping. Learn More
  • ASIN: B00409E4JK
  • Item model number: UNU-DX-04-1700B
  • Batteries 2 Lithium ion batteries required. (included)
  • Average Customer Review: 3.6 out of 5 stars  See all reviews (1,728 customer reviews)
  • Amazon Best Sellers Rank: #24,877 in Cell Phones & Accessories (See Top 100 in Cell Phones & Accessories)
  • Product Warranty: For warranty information about this product, please click here

Customer Reviews

Top Customer Reviews

Package Type: Standard PackagingColor: White Verified Purchase
Length: 7:14 Mins
I don't normally write too many reviews but I had to write something about the Unu DX-1700. I've spent a great deal of time doing cross comparisons of different battery cases on the market before I settled on the Unu. There is relatively very little information on the web about the unit so I figured I'd help out buyers like me who like to research the item before they commit to buying. So here goes:

The Good:
1. The Unu is attractively priced. Many other battery cases range anywhere from $60 - $80 which is way out of my price range for this type of product.
2. The Unu looks good. I've got a white iPhone 4 (Verizon) and a majority of the battery cases out there are black. Also, the Unu has a nice, glossy finish which compliments the iPhone.
3. It works. I can go an entire day (13 hours) without recharging my phone, and that includes web surfing, sending/reading emails, and of course playing games.

The Bad:
1. The Unu does add some considerable bulk to your slim iPhone. Both in thickness and in height.
2. The Unu adds extra weight (mainly from the battery) so throwing it in your pockets may be uncomfortable.

It's a quality battery case that works well, compatible and reliable, and is relatively inexpensive. There are negatives, but they're all superficial. If you're a person who is always on the go and you don't always have time to charge your phone then this case is for you. I've had my Unu for nearly 4 months, and it has saved me on many occasions, particularly last week when heavy winds knocked down all the electrical lines and our neighborhood had no electricity for 3 days. Outstanding product - gets 8 out of 10 stars from me.
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Package Type: Standard PackagingColor: Black Verified Purchase
I was delighted to discover these little gems were still offered by Amazon, and at a slightly reduced price from the first one I purchased a year ago.

Back then, when the iPhone 4 was first released, there weren't many "power case" options available. I found this one, freshly listed by an unknown-to-me seemingly Chinese company and I hesitated. Long enough for someone else to leave a review. (Thanks Crispin38!) After all, I frequently haunt the "wholesale direct" websites and the quality often leaves much to be desired.

When that first review arrived and it was positive, that was good enough for me to take a chance and keep my fingers crossed, and am I ever glad I did.

Mechanically, the case fits rock solid. No gaps or sloppy contact points along the seams, and the snap-together closure seats firmly into place. The end result is a trim, slightly thicker than before phone which fits confidently in my grip, with no slippery or "too thin" sensation. Turned to landscape mode for two-thumbs typing, the size is just right for my large hands to reach any key present.

Electronically, the case delivers pretty much as promised, so long as you explicitly follow the manufacturer's admittedly sparse instructions. Unu presents this case as a "recharger," rather than an ongoing power supply, meaning that they recommend turning the device on only after the phones internal battery is depleted. Used in that fashion, the case consistently recharges the phone battery from 20% to 100% every time, though the "power low" warning light starts flashing at around 85% or so.
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Package Type: Standard PackagingColor: White Verified Purchase
I was hesitant to try this knockoff batt case... but trusted the other review on here. It is very sturdily built and provides lots of boost. I love the sync passthrough that is only available on the cases that cost double and not on other alternatives. The only two drawbacks I've found are the added weight/bulk (duh.. to be expected) and you cannot use the camera with flash at night inside this case. It reflects off the white and blurs out the picture. Really not a deal breaker for me.

I cannot suggest this case enough as an alternative to the higher priced cases. Love it for the weekends when I am not around power all the time. This case holds my VZW iPhone 4 at 100% for at least 24 hours with heavy usage... plus then I have a full iPhone batt after that!

9/10 :)
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Package Type: Standard PackagingColor: Black Verified Purchase
I bought 5 of these, 3 white & 2 black. I've had about 10 different battery packs for all generations of the iPhone except the 1st one. I'm a heavy user with podcasts, games, foursquare, facebook, google maps, etc. and I've had the uNu battery pack for about a month. Compared to the Mophie Juice Pac Plus:
- Much cheaper at US$35 vs. US$100
- While the dimensions are about the same as the Mophie, it feels bigger. Maybe it's because the Mophie has rounded edges & this one is angular
- While it's advertised as 1700 mAh, it feels like less. More like 1200. After charging all night, the Juice Pac plus (2000 mAh) can last me more or less till when I get off work before the iPhone's battery indicator starts to go below 100%. With the uNu, it goes below 100% at about lunch time. Maybe it's the chemistry.
- The micro USB connection is stronger than the Mophie. The reason I'm trying the uNu is because I've broken 3 Mophies. I would invariably knock the iPhone off the table while it was charing and snapped the Mophie's micro USB connector after which the Mophie would not charge. What a waste of US$100 x 3. I've continue to knock my iphone off the table & so far, so good.
- the micro USB cable it comes with is crap - I broke mine when it bent just a little.
- The case is good protection same as the Mophie - my iPhone 4S was knock out of my hands on to the sidewalk (I was 4squaring) and it bounced on the concrete. The uNu's upper left corner is cracked but the iPhone is fine. The battery still works great.

The big Mophies & the longest lasting battery packs I've had (I had one that had a solar back recharger) usually lasted me about 6 months before they would stop taking a charge. Will report back when this one dies. I suspect this is 1/3 the price partly because it won't last as long.
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