Every one has those cordless tools in the house or truck that are lifesavers . For years I have used Ryobi 18+1 tools drills circular saw , reciprocating saw and work light oh yea sander .I have 6 batteries that are shot 1 works for less than half what it did when new. A new battery will cost 35$ the tools are old battery technology I will replace with the new lithium ion ones some day. Right now I have tools that for all purposes are use less .
As I have been helping my son at his place being without power for plug in tools and my cordless ones being useless it has been a problem .Today it was a high of 30 outside so I was bored ! Went on instructables and found several things on how to make a 18 volt cordless tool work off a 12 volt car battery. Now I know it has a cord but when nothing is available in the middle of the woods even a corded tool is great . I disassembled a dead battery gutted it to the leads and taped in 2 10 foot leads + and - crimped on alligator clamps to the other end . To test it I used a jump pack , popped the gutted wired 18 volt base in my circular saw snapped the clips on the jump pack worked great a little less powerful but very useable .Tested it in all the tools and was well pleased.
Now this may not seem important but I had a 150$ worth of useless tools that now I can use anywhere I have my truck. It cost me 0$ and took less than 30 minutes to do. Using a jumppack makes it very portable on a job. I have a 800 watt inverter that I use/keep in my truck but that wont run a saw or drill .I would love to have a 2000/4000 watt inverter but hard to justify at this time that kind of money. Cost of 0$ vs 200$ is a no brainer .
If you have cordless tools and no or dead batteries check out the How to ,or Instructables sites !!! http://www.instructables.com/answers/Is-it-possible-to-operate-18Volt-power-tools-from-/ or https://www.youtube.com/watch?v=VCcbnNtyfyU