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How to make a charger to charge a 12-volt battery

Updated February 20, 2018

Twelve-volt batteries are often used to provide electrical energy in automotive applications. Twelve-volt batteries are also used in marine applications, as the filter device in an uninterruptible power supply and as a power source for portable electronics.

To properly maintain a 12-volt battery, the battery must be charged periodically. Trickle-charging is an effective and safe method for charging a 12-volt battery. A simple trickle-charger can be fabricated from a DC adaptor and battery clamps.

Snip the tip from the adaptor. Pull the wires apart until there is a 6-inch separation between the wire ends. Strip 1/2 inch of insulation from each wire end. Place a piece of electrical tape over the positive wire (which is the wire that formerly connected to the centre conductor on the adaptor tip).

Loosen the retaining screws on the battery clamps. Place the negative wire into the space created by the loosened retaining screw on the first clamp, and tighten the screw until the wire is held firmly. Solder the wire to the retaining screw.

Remove the electrical tape from the positive wire. Place the positive wire into the space created by the loosened retaining screw on the second clamp, and tighten the screw until the wire is held firmly. Solder the wire to the retaining screw.

Attach the positive wire battery clamp to the positive battery post. Attach the negative wire battery clamp to the negative battery post. Plug the DC adaptor into a wall electrical socket.

Tip

A trickle-charger is intended to charge a battery over several hours. Check the battery every two hours. If the battery is warm to the touch, continue charging the battery.

Warning

Do not charge the battery for more than six hours. If the battery gets hot to the touch, unplug the charger and remove the battery clamps immediately.

Things You'll Need

  • 1 12-volt DC adaptor
  • 2 battery clamps
  • Flathead screwdriver
  • Electrical pliers
  • Vinyl electrical tape
  • Electronic (rosin core) solder
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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.