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How to build a 36-volt battery charger

Updated February 20, 2018

Secondary-cell batteries, such as lead-acid and nickel-metal hydride batteries, require periodic recharging to maximise battery life. For most secondary-cell batteries, finding a charger is relatively simple. However, if there is a secondary-cell battery with an uncommon voltage, such as a 36-volt battery, building a charger rather than trying to find one may be more economical.

Snip the tip off the AC adaptor. Pull the adaptor wire ends apart until there is a 6-inch separation between the ends. Strip 1/2 inch of insulation from the wire ends.

Attach one of the adaptor leads to one of the transformer primary terminals. Solder the adaptor lead to the terminal. Solder the remaining adaptor lead to the other terminal on the transformer primary.

Cut four pieces of wire, and strip 1/2 inch of insulation from each wire end. Attach one end of the first wire to one of the terminals on the transformer secondary. Attach one end of the second wire to the remaining terminal on the transformer secondary.

Twist together the cathode lead, which is marked with a line on the diode case, from the first diode jointly with the free end of the first wire and with the anode lead from the second diode. Solder the electrical joint.

Twist together the cathode lead from the third diode jointly with the free end of the second wire and with the anode lead from the fourth diode. Solder the electrical joint.

Twist together one end of the third wire with the anode leads from the first and third diodes. Solder the electrical joint. Slip a ring terminal over the free end of the third wire, and solder the wire to the terminal.

Twist together one end of the fourth wire with the cathode leads from the second and fourth diodes. Solder the electrical joint. Slip a ring terminal over the free end of the fourth wire, and solder the wire to the terminal.

Tip

To charge the battery, connect the ring terminal at the end of the fourth wire to the positive battery terminal. Connect the ring terminal at the end of the third wire to the negative battery terminal.

Things You'll Need

  • Twelve-volt AC adaptor
  • Electrical transformer
  • Electrical wire
  • Electrical pliers
  • Four 1N4152 rectifier diodes
  • Electrical wire
  • Electrical pliers
  • Electronic solder
  • Soldering iron
  • Two ring terminals
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About the Author

David Sandoval has served as a trainer and technical writer since 2000. He has written several articles online in the fields of home improvement, finance, electronics and science. Sandoval has an Associate of Applied Science in microelectronics from Northern New Mexico College.