The Mili Powerspring is a protective rigid case that can nearly double your iPhone's battery life.

For all its touchscreen app wonderfulness Apple’s iPhone has one big problem – its battery life.

Partly this is a problem of its own making. The iPhone can do so much (web browsing, email, video playback, video making, audio playing, app games, GPS, etc) that its battery takes quite a beating over a day’s use.

Most iPhone users need to charge their battery at least every other day if not daily.

(By the way, here’s Apple's own tips for optimising the iPhone’s battery life.)

If you’re an iPad user you’ll be even more exasperated with the iPhone’s battery life, as Apple has done a great job with its tablet’s charge.

It would help if you could swap out the iPhone’s battery, as you can with the Google Nexus One smartphone, but that’s not the Apple way.

Most iPhone users keep a power-charging cable at home and in the office to ensure their beloved smartphone doesn’t conk out halfway through the day or just before that important journey or meeting.

But it’s not always convenient to charge, and often it’s too late to give the mobile anything more than a sudden 10-minute surge – which won’t last long at all.

There are several battery packs available for the iPhone (Griffin’s PowerBlock, Kensington’s Mini Battery Pack, Power Traveller’s PowerMonkey, and Scosche’s SolBat 2, for example).

There are a few iPhone battery packs that double up as protective cases: Mophie’s Juice Pack Air, and Mili’s Powerskin and Powerspring.

Mili Powerspring iPhone battery charger case

At the moment these cases fit the iPhone 3G and 3GS only, although I’m sure an iPhone 4 Powerspring will be out soon.

While the Juice Pack Air’s case is slightly slimmer than the Mili cases we prefer the Powerskin and Powerspring because they’re better at the primary function of recharging the iPhone’s battery.

The Juice Pack Air doesn’t pack as much juice as the Powerskin/spring cases, it has a 1200mA capacity compared to the Powerskin/spring’s 2000mA.

(The Power Traveller PowerMonkey Classic V2 charger offers an even greater 2200MA capacity, but it’s an extra device to carry around with you rather than a functioning case like the Powerspring or Juice pack.)

Mili claims that the Powerspring “virtually doubles” the life of the iPhone battery and when turned on at 20 percent of iPhone battery charge (when the iPhone’s charge bar turns an ominous red) on average it will charge it up to about 90 percent. Over a couple of weeks of testing we never got the Powerspring to bring the iPhone back up to full charge but the claim isn’t far off.

The Powerspring doesn’t automatically switch itself on. Instead there is a switch on the side that turns the charging on – so you can charge your iPhone whenever you want to, whether the battery is at 50 percent or 20 percent.

When your iPhone charge reaches 100 percent, the Powerspring turns off ready to be turned on again later if need be. This way you have the maximum control of when and for how long you use the Powerspring for and so make the most out of the available charge. Also there is an indicator on the side of the Powerspring, right next to the Power button, which shows you how much power is left in the Powerspring. 

Mili recommends turning it on at about 20 percent of the charge, when the iPhone warning shows low battery.

Once the Powerspring has been turned on, it will act as if you plugged your iPhone into the wall socket charger. The extra charge is available immediately.

The £44.95 Powerspring is a more flexible version of the £43.95 Powerskin, with a spring-mounted head that allows you to simply slip the iPhone neatly into the otherwise rigid case shell. The Powerskin’s design has a detachable head that must be removed to fit the iPhone. The benefit of not having a two-piece design is well worth the extra pound.

The shell case does make the iPhone bulkier but with minimal additional weight. I got used to the extra heft pretty quickly, and all concerns about such matters quickly disappear when you get to use the extra power as soon as the iPhone’s charge bar suddenly goes red.

Powerspring colours

The Powerspring is available in six colours, although it’s only really the outer-shell black or white you’ll actually see when the iPhone is in place: Black, Black & Blue, Black & Green, Black & Grey, White, and White & Orange.

The Powerspring is charged via USB rather than the iPhone’s 30-pin dock connector. While this means finding somewhere else on your desk to place another cable it does mean you can charge the Powerspring at the same time you charge the iPhone via both sides of a keyboard’s USB slots, for instance. Having two USB cables would be useful, though, so you could charge the Powerspring at home and at the office without having to carry it with you to and fro.

Powerspring: Specs

  • Compatible with Apple iPhone 3G and Apple iPhone 3GS
  • Compatible with Apple iPhone 3G and Apple iPhone 3GS


Having an extra charge of power for your iPhone hidden in a protective case rather than as an extra device to plug in, mislay or lose is a great idea. The benefit of the 80-90 percent supplementary battery life far outweighs the bulkier iPhone. Until Apple refines power usage or someone invents the ever-lasting battery Mili's Powerspring is an iPhone battery life saver.

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