Top critical review
48 people found this helpful
Works, but not very efficient, and also it smells!
on April 23, 2011
Pros: Cheap, provides consistent voltage, good current, and easy to use.
Cons: Cover very difficult to get off, LED is almost useless (super dim, although can be used as a battery life indicator), Switch can easily be turned on while in pockets, device does not handle high currents very well (creates noxious, burning plastic smell in charging currents >500mA), conversion is 5V is inefficient (loses much of the energy to heat).
Other thoughts: The D+ and D- on the USB port is shorted so that some devices (e.g. mobile phones) charges more quickly using higher currents than ordinary chargers. When the device is switched on, it provides a constant 4.98V on the USB port, even when the batteries themselves approach 1.0V. While the device is off, the voltage will slowly go down from 4.98V to the voltage of the installed batteries (possibly due to capacitance?).
Overall, this is a good device for its price. However, I would not really use it as your ordinary backup charger because it has a serious design flaw. Depending on what you are planning to charge using this device, it might work for you. However, as stated on the package itself, this device is only designed for an 500mA output. That being said, since D+/D- is shorted, many phones recognize this as an AC source and draws currents up to 1A. This is a huge problem since the internal circuits get so hot that it essentially melts something (plastic?) inside (you will soon notice a burning plastic smell if you plug this in a high current drawing device like an iPhone). Also with this great amount of heat generated, many of of battery's stored energy is lost to heat rather than charging your device (to be expected since you are upconverting ~2.5V to 5V). Using a freshly charged set of 2100mAh NiMHs, I was able to charge my LG Optimus S ~24% (3.7V Li-Ion, 1500mAh) before the batteries themselves die completely. That gives an overall charging efficiency of just ~25% (again expected since there is so much conversion inefficiencies in the process...)
Overall, good for emergencies, although not very efficient at all (gives out heat and burning plastic smell)... If you don't mind those, then this is a good deal. :)