If you’re looking for a simple way to charge most of your mobile gadgets, the Kensington Pocket Battery might be for you. As you can see from the image, it packs both micro and mini USB connectors(both of which can be used simultaneously) for charging your electronics. The underside sports a standard USB connector for charging the battery itself. The Lithium Polymer battery has a quoted capacity of 1200mAh(see below for further elaboration). Output is rated at 5V and up to 1A. Total weight is 1.76oz. The unit retails for $39.99 but I managed to pick one up from Amazon for $13. The price has since gone up to $20.
Physically the battery is larger than internal batteries of similar capacities. But you have to keep in mind that there are charge controllers and converters inside to make this thing compatible to a variety of devices. All in all, it’s a manageable size and the weight is very light. There are two LEDs located on the front of the battery. A green one for when the battery is above 30% and red is displayed when it’s below 30%. The indicator lights are only turned on when you press the button located next to them. The case is covered in glossy plastic and becomes easily scuffed. On either side you will find a micro and mini USB cable tucked neatly into the case. They are firmly tucked away but still easily accessible, a good balance. On the underbelly is the full USB used for charging. You can plug it into any powered USB port for charging. The battery can still be used while charging, so you can hook up two devices to the battery while it’s charging and have all three devices charging at the same time from just 1 USB port.
Charging the battery from empty takes approximately 1 hour. To turn on the battery for charging, you must press the battery indicator button. After about 10 charging cycles it managed to boost my Dell Venue Pro’s battery from 14%(230mA) to a decent 63%(1024mA). I used the EM app to read the percentages and mA capacities(I should note that the full battery capacity reads as 1644mA in the app and not the 1400mA printed on the battery). That’s roughly an 800mA increase. Considering the Kensington battery is rated for 1200mAh I was slightly disappointed.
However, I noticed they never published the battery voltage used. With a little math(Watt-hours = Amp-hours * Voltage) I discovered that the only way the rated 1200mAh works with the math is if it’s paired with a 3.7V output. Since the actual output is stated as 5V(not sure how they increase the voltage on the battery as I’m not an electrical engineer) I recalculated the capacity by dividing the 4.44Watt-hours by the 5V output. This gave me a capacity of just 888mAh. This lines up almost perfectly with the charge I managed to squeeze out of the battery(the phone was on while charging). As I stated, I’m not an electrical engineer, so if anyone wants to correct me here please feel free to do so in the comments. I’m always eager to expand my knowledge!
Bottom line, with OEM batteries running around $50 a pop, if you can find this for under $20 it’s a steal. Even at $20 it’s a nice backup to have since it can juice any device with a micro or mini USB charging port.