How To Make A Low Cost Trickle Charger

Have you ever been in that situation where you needed a Battery recharged?Say a Boat,some sort of recreation type vehicle or a car that very seldom gets driven?Well all you need is a 12 volt plugpack from a cordless phone,drill or cell phone. Most plugpacks have a current rating anywhere from 200ma(1/5amp)to 850ma(7/8amp)the higher the better.Most plugpacks produce @ 14 to 18 volts with no load.Snip the end off,seperate the 2 wires. Find the + lead, then - lead.If voltage is @ 13 to 14 volts it is good to go.Now if you use this to try an charge a complete dead battery you will need to add a resistor. 5 watt 5 ohm will do.All your are doing is slowing down the flow.Resistor goes in on + side in series.If the Resistor gets hot increase the Wattage.All the Aligator clips and Resistors are available at Radio Shack. Now for that added safety feature you can put a Diode a head of the Resistor to prevent Voltage from feeding back into the plugpack.Treat this as a full-on Battery charger when it comes to hook-ups as it will end with the same results if hook-ups are incorrect.

One of the best things I like about this compact battery charger is you can wrap it up,take it with you and use it with a 12 volt automotive converter or portable generator. This unit does not draw enough amps to worry about blowing fuses or tripping circuit breakers.