We’ve found the iPhone battery life an improvement on our last (Windows Mobile) phone and it sometimes goes 2 days between charges if it gets light use. However a few weeks ago, on a particularly long business trip to London, the iPhone let us down and died. Admittedly this was a day that started at 5:00am, included video playback whilst waiting in the airport departure lounge, lots of voice, text and email as well as extensive use of Google maps plus having the Wi-Fi turned on all day.

The battery final gave out around 7:00pm, 2 hours short of our business meeting ending. Ok so 14 hours hard use is extreme in one day, and we really should have turned off Wi-Fi and dropped the screen brightness back had we know it was going to be such a marathon. But determined to ensure this won’t happen again, we set about investigated external batteries for the iPhone. After lots of searching we settled on the bargain USB Li-Ion Battery Pack from Portable Power Supplies. Check out the Video and the full review after the jump...

It’s supplied with a strip of self-adhesive Velcro so it can be fastened to the back of the device you want to power. Hmmm, I’m not ready to deface my iPhone with this sucker any time soon but perhaps this would be acceptable on some other phones, PDAs, digital cameras, GPS navigators or personal media players that support USB charging.

We then let our iPhone drain down until it hit the red 20% battery warning. Reversing the supplied cable so that now the large USB plug gets inserted into the socket labelled “OUT” you then swap the mini-USB on the other end of the cable to the iPhone/iPod tip and plug it in.

Press the power button on top of the unit turns it on and the iPhone begins to charge. It reached 100% in a little over 2 hours. Excellent. The unit still wasn’t showing its warning LED for low battery so we repeated the process to see if we could recharge the iPhone a second time from the external battery’s single charge. This time, just short of the 2 hours, the battery did die. However it managed to charge the iPhone to around 90%! We’d expect the Li-Ion battery to last a bit longer after cycling it a few more times too meaning 2 full charges should be easily achievable.

The shape and size of the device means it’s nice and flat and would easily slip into a suit or even a jean pocket along with its retractable cable. So potentially you could leave home with your iPhone fully charged, and get a second and third day out of it without ever having to carry your charger or find a mains outlet. For a small outlay this is an extremely useful device if you own an iPhone and with the huge range of other devices supported, at the price it's a no-brainer.

Available now from - www.portablepowersupplies.co.uk

List of Some of the Supported Devices:
* Archos - AV100 series, AV300 series, AV400 series, AV500 series, AV4100, All Gmini models xs100 120 xs200 xs202 220 400 402 500 etc, Jukebox Multimedia 10 & 20, FM Recorder 20 & V2. NOT Compatible with the AV700 Series.
* Creative - Zen PMC, Zen Touch, Zen Xtra, MuVo² Series, Zen NX, Jukebox 2, Jukebox 3, Zen Vision:M (subpack / dock not supplied), all models which charge from a mini-USB socket. Travelsound speakers.
* Garmin - All in-car GPS units plus many others.
* iRiver - H100 Series, (also known as the 'iHP' series), H10 (using AC charging lead supplied with player), PMP Series, iGP100, H300, H320, H340.
* Motorola - RAZR series including - RAZR V3, RAZR V3i, RAZR V3X, PEBL U6, SLVR L7/M300, L2/L6, A780, A910, E770v, E1070, V360, V235, KRZR K1m, A1200, A668, A70, A732, C305, C362.
* Mustek - PVR-H140 H240.
* Nokia - all phones using original DC3.5 plug including - 9300, 7380, 7360, 7270, 6610I, 6170, 6100, 6060, 6030, 6021, 6020, 5140I, 5140, 3230, 3220, 3100, 2650, 2600, 2300, 1600, 1110, 1100, N-Gage. Phones with the smaller plug are also compatible if using the adaptor supplied with the phone.
* Sony - PSP, HD1/3/5.
* RCA - RD2780.
* Thomson - RD2780.
* TomTom - MOBILE 5, NAVIGATOR 5, NAVIGATOR 6 + GPS receiver, GO, GO 300, GO 500, GO 510, GO 700, GO 710, GO 910, ONE - 1st Edition, Rider
* Apple iPod Charges any iPod with a colour screen, adds 60+ hours extra playtime.
* Ericsson A2218Z, A2218z, R300LX, R300d ,R300z, T28 WORLD, T28z, T39m, T60d.
* Samsung A200, A288, A310, A210, A399, A475, A505, A509, A539, A561, A563, A564, A591, A592, A595, A599, A610, A809, N181, N182, N191, N195, N370, N375, X199, X209, X219, X309, X319, X359, N391.
* Sony Ericsson A2618, A2628, A3618, J300, K500, K700, P800, P802, P900, P908, P910/a/i, R300, R310, R320, R520, R600, S700, S710/a, T20, T28, T29, T39, T60, T61/c/d/lx/z, T62u, T66, T68i/m, T100, T105, T106, T200, T226, T230, T237, T290, T300, T306, T310, T316, T600, T608, T610, T616, T618, T637, Z200, Z300, Z500a, Z600.