Simple Battery Charger
First of all, I am into electricAL stuff, not electrONIC. Circuit boards, chips, transistors and small electronic parts and me do not get along together. Beleive me, if I can do it, ANYBODY can.
Transformers get warm and heat is wasted energy. This battery charger uses no transformer and can be made for around $25 if you buy anything new. If you are a junk collector like me you cam probably build it out of your junk collection for nothing.
It consists of ......
1- full wave bridge you can get at radio shack for $3.29 http://www.radioshack.com/product/index.jsp?productId=2062584&cp
1- incandescent light dimmer switch
1- 12V volt meter you can get at any auto parts store
1- 0-10 amp meter you can get at a electronics shop or sometimes at a place that has parts for tractors.
4 solderless connectors to fit the full wave bridge
2- Battery clamps from an old battery charger or for a couple of bucks at radio shack or the hardware store
1- power coard off some broken electrical something -or-other.
1- plastic box of some kind to build it in
3 feet of 10 or 12 gage stranded wire color coded red and black.
The full wave bridge is marked positive and negative and the dimmer switch goes in the hot wire (small prong or black wire) of your AC input. The volt meter is marked positive and negative.
Here is the schematic. It's real simple and needs no explanation.
NOTE: never charge a battery to more than 14.5 volts. The first time or two keep close watch on your charger. You will notice that as the dead battery charges, the volt meter will raise higher than when you started. Set the voltage to about 2 volts above what the meter reads when you first hook it up to the battery before you turn it on. When the battery comes up you can increase it a little till you get to 14.5 volt max. When the battery is charged and the amp meter drops back to zero, you can turn it off. After whilke the battery will probably drop back to 12 or 13 volts, especially if it is older. That is expected.
DISCLAIMER: This is not a HOW TO page. This is how I did it. I do not recommended that you attempt to duplicate this project. Go buy your own battery charger at Walmart. This project uses high voltage that can kill you. You can also damage your batteries, produce explosive gasses from the batteries and get acid burns from handeling battries or when they explode blowing the side out of your house and burning it to the ground along with your neighbors house.