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  • Convert a perfectly good cordless drill to a corded one

    I went a step further than this. One doesn't always have a a car handy, and a 12V battery is a bit heavy to lug about. So I made a much smaller lightweight replacement using six 500 Farad supercaps wired in series. This will happily keep you going with a hundred or so medium sized screws into pine before requiring to be recharged.This is where supercapacitors really come into their own. If you use a constant current charger capable of supplying 20 Amps, it takes about 30 seconds to charge.(I built my own. Two transistors, a handful of resistors and a fan cooled PC processor's heat sink I had hanging around) and off you go for more happy trouble free screwing! My charger will work from a car battery or a mains supply (I bought a mains 20Amp 12v supply from the internet for about £...see more »I went a step further than this. One doesn't always have a a car handy, and a 12V battery is a bit heavy to lug about. So I made a much smaller lightweight replacement using six 500 Farad supercaps wired in series. This will happily keep you going with a hundred or so medium sized screws into pine before requiring to be recharged.This is where supercapacitors really come into their own. If you use a constant current charger capable of supplying 20 Amps, it takes about 30 seconds to charge.(I built my own. Two transistors, a handful of resistors and a fan cooled PC processor's heat sink I had hanging around) and off you go for more happy trouble free screwing! My charger will work from a car battery or a mains supply (I bought a mains 20Amp 12v supply from the internet for about £15 and tweaked it a bit to supply 17v)Supercapacitors make lousy batteries. They hold a much smaller charge, and have a high self discharge rate. But they can supply current at up to 1,000A or more and be charged in seconds rather than hours. They are a fraction of the weight and size too and this makes up for it in this application. The high current capability makes the screwdriver able to supply MUCH higher torque than the original batteries too, should you want need it. My supercapacitors are mounted in a plastic box and weighs a bit more than a pound. It is about 6" by 4" by 3" and was manufactured by Messrs Tupperware. I added a cheap digital voltmeter to it as a sort of fuel gauge. The energy it contains is proportional to the square of the voltage so it is not exactly linear, but it gives you an idea of when to go charge it up again with experience.

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