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How to Build a Simple 12 Volt Battery Charger

by David Sandoval

If a lead-acid battery is charged too quickly, the battery can overheat and give off flammable hydrogen gas. To minimize the chances of charging a lead-acid battery too quickly, you may choose to charge the battery with a trickle-charger. A trickle-charger need not be an elaborate electronic circuit; in fact, a simple 12-volt battery charger can be constructed using a DC power adapter.

Step 1

Cut the tip off from the end of the power adapter, and mark the positive wire with the permanent marker. Pull apart the adapter wires until you create a separation of approximately six inches between the wire ends. Strip off half an inch of insulating material from each wire end.

Step 2

Insert the stripped end of the adapter’s positive wire into one of the ring terminals. Crimp the terminal to the wire.

Step 3

Use the permanent marker to label one of the crocodile clips with a "+" sign. Remove the top screw on this clip, and insert the screw through the roundel of the positive wire’s ring terminal. Insert the screw back into the screw hole, and tighten the screw so it holds the ring terminal firmly to the crocodile clip.

Step 4

Insert the stripped end of the adapter’s negative wire into the remaining ring terminal. Crimp this ring terminal to the end of the adapter wire.

Step 5

Remove the top screw on the unmarked crocodile clip, and insert the screw through the circular part of the negative wire’s ring terminal. Insert the screw back into the screw hole, and tighten the screw so it holds the ring terminal firmly to the crocodile clip.

Attach the positive crocodile clip to the positive battery terminal. Attach the negative crocodile clip to the negative battery terminal. Plug in the battery charger and allow the battery to charge for at least four hours.

Items you will need

  • 12-volt DC power adapter
  • Electrical pliers
  • Two crimp-type ring terminals
  • Permanent marker
  • Screwdriver
  • Crocodile clips
  • 12-volt automotive battery

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