When I went to leave home the other day, my Android smartphone was off. I never turn if off. The battery had drained so low that, I assume, it shut itself down to insure that there is some juice left for emergencies. Powering it on showed the battery was about 5% charged.
I had screwed up my normal charging routine and was forced to leave home with an all-but-dead cellphone.
Yet, when I returned a few hours later, the phone was completely charged.
While sitting in my briefcase, it had been charging from an external battery that I had purchased for just this sort of thing. Classic Defensive Computing.
The battery, shown below, is fairly small, roughly 3 inches wide by 2 inches deep and .75 inches tall when laid flat. The USB flash drive in the picture provides another perspective on the size.
There isn't much to operating the battery; a switch turns it on and off, and three LED lights indicate the charge level. I keep it near my cellphone and set a reminder in my calendar to charge it every three months.
Some external batteries are charged by a USB port, others can be charged from an AC outlet. While I prefer an AC outlet, this particular model charges itself via USB. On the other end, the only connection to your battery-using device offered by this particular battery is a USB port. Other external batteries offer more connections.
So, I am not going to claim that this is the best external battery, or even a good one. And, being a blogger rather than a lab, I am not going to measure how quickly it charged the phone or how many hours of life it can provide an iPad (for a bit of that see Ars Technica
What I will do, is hope that this story inspires some Defensive Computing in readers.
Why the headline? I bought the battery about nine months ago and didn't get any use out of it until now. Like buying insurance, you hope to never need it.