This is just a quick little how to to demonstrate a quick project to put some surplus components to use with minimal tools. (how I came across the component is encapsulated in brackets)
1.8W Solar battery maintainer. ($3 at a yardsale)
12v cigar outlet (removed from truck when hard wired emergency lighting)
1" square of servo tape. (double stick foam tape left over from another project)
5Ah 12V sealed lead acid battery. (salvaged from UPS pack)
2 female blade connectors to fit the battery. (misc components from electrical connector bin)
USB/car Phone charge cable. (I had a duracell 2 USB 12v cigar adapter in my car)
Wirestripper with Crimp tool
I was at a yard sale where a older gentleman had the 12V solar battery maintainer for sale. as it was $3 I could not just let it sit there and it wound up in the "parts" bin just waiting for a small scale solar project like this.
After some time I had a 3000VA UPS report a battery failure. I always take apart the battery pack as only 1 or 2 of the 12v SLA batteries are actually bad as they are wired in series and parallel a 3000VA usually has 8 12V 5Ah batteries in the pack wired for 24V. As long as one of the batteries show more then 13 volts it is most likely good for at least a little while for tinkering or projects. If you dont work in IT it would not hurt to ask your local IT guy if they have a UPS fail if you can pick up one of the batteries. I just cant have good junk hit the recycler.
Assembly, Since this build uses common off the self components assembly is pretty straight forward. However one must take into account battery polarity and electrical safety. I omitted an inline fuse as both my panel and the USB adapter have a fuse in the plug end.
1 Crimp blade terminals to the positive and negative leads of the cigar outlet.
2 Apply "servo" tape to flat side of outlet.
3 Connect outlet to corresponding terminals of the battery.
4. Position outlet to battery, remove backing and affix the outlet to the battery
5. Plug in solar panel
6. Plug in and charge cell phone.
Granted one can make this as complicated as you want, with super-capacitors, a 3 cell LiPo pack and some fancy charge circuitry, But I wanted to showcase a gadget that can be built with stuff laying around or easily found. I like to keep it stupid simple.