If you find you need a little more juice, to power your iPhone 4 during day or need a few hours extra while travelling to view those movies. The Exolife Power & Protection rechargeable (1500 mAh) battery pack by Exogear might be worth a look.
The Exolife battery pack comes in a presentation case and includes the Exolife case and a USB re-charger cable. The Exolife measures only 2.44″ x 5.1″ x 0.59″ weighs just 59 grams around 2.08 ounces.
After removing the battery from the packaging I was surprised how small the battery pack was compared to others I have used considering the amount of extra power it provides your iPhone 4. To fit the case to your iPhone simply detach the side of the Exolife battery pack and slot your phone onto the connector, once in position, snap the side of the case back into place.
The battery case seems designed as a semi-permanent addition to your iPhone. As removing and re-inserting your iPhone on a continually basis may put extra stress on the more delicate parts of the Exolife surround near the volume controls.
Once fitted the Exolife battery pack adds a little extra weight as expected but nothing that would hinder the use or function of the new iPhone 4. If anything adding the battery made the iPhone 4 feel a little more like the iPhone 3GS with its rounded corners and smooth gloss plastic back.
The battery pack is sculptured around the camera lens and flash as to not hinder the focus or picture and includes cut outs on the side for volume and power switches on the top. At the bottom there is a USB 2.0 port protected by a rubber cover and a power switch for the battery itself. Allowing you to turn it off if required. On the rear of the case if a battery charge strip showing you the charge remaining the Exolife.
While the Exolife is attached to your iPhone, syncing and charging are all completed using the included USB cable and the Exoclear surround of the case helps prevent any problems you might encounter from the iPhone 4 death grip.
With the addition of the Exolife on your iPhone expect the life of your phone to double. With Exogear says it will provide 300 hours of standby, 7 hours of Talk time and 6 hours of additional surfing. The Exolife is also fitted with a Exosave feature that saves energy in the battery by turning it off automatically when not required.
Personally if I needed extra juice on the go the Exolife would definitely be my choice due to its slim nature and iTunes syncing abilities. However I would need to take care positioning the clear side surround when adding and removing the Exolife, especially around the volume controls. Overall a great piece of kit.
You can find out more details about the ExoGear Exolife battery pack over at ExoGear. It is also available in the UK from Exolife.