How to Build a Battery Charger Circuit

Written by william kinsey
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How to Build a Battery Charger Circuit
Battery Charger (power supply image by pmphoto from

Batteries are used to supply power to many different types of equipment, from CD players to toys to watches. The increase in environmental awareness has brought a gradual shift to rechargeable batteries, which can be reused once they're recharged in a battery charger. Doing so reduces the number of batteries that end up in landfills. Rechargeable batteries save money in the long run but cost more upfront; some people find it useful to build their own battery charger.

Skill level:

Things you need

  • Wire strippers
  • Wire cutters
  • Power transformer (the transformer output voltage should match the voltage of the battery that will be recharged)
  • Bridge rectifier
  • Switch
  • 16 gauge electrical wire
  • 6 feet of 16 gauge electrical wire equipped with an electrical plug

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  1. 1

    Strip half an inch of insulation from the ends of the wire equipped with the electrical plug. Connect one of the two wires to one of the terminals on the primary side of the transformer. Connect the other wire to one side of the power switch. You'll use this to turn the charger on and off.

  2. 2

    Connect the other side of the switch to the remaining terminal on the primary side of the transformer.

  3. 3

    Connect one of the transformer's secondary terminals to one of the input terminals on the bridge rectifier. Connect the other secondary terminal to the second rectifier input terminal.

  4. 4

    The rectifier has a positive output terminal and a negative output terminal. Connect the positive terminal to a red wire and the negative terminal to a black wire. The type of battery you'll charge with this charger will determine what you put on the ends of the black and red wires. If this is to be used to charge a car battery, for example, alligator clips would be best because they can clip onto the battery posts.

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