Although most batteries charge using DC electricity, most battery chargers themselves work from an AC power supply. A battery charger that is powered by AC will then convert the power to a low-voltage and low-amp DC supply. In fact, a battery charger that operates specifically under DC power may convert the current to AC and then back to DC in order to account for the shift in voltage necessary to properly charge the batteries. Read on for tips on how to make and operate a battery charger using DC current.
Step 1 - Determine the Voltage of the DC Power Supply and the Battery
The first step toward recharging your batteries from a DC power source is to determine the voltage necessary to recharge the batter as well as the voltage available at the source. Examine the power supply for an indication of the voltage. Typically, cars provide 12 volt power while boats typically provide 24 volt power. At the same time, examine the battery for the necessary voltage to charge. This number may be provided on the battery itself, or it may be the same as the output voltage of the battery-powered device attached to the battery.
Step 2 - Acquire a DC/AC Inverter
A DC/AC inverter transfers DC electric power into AC power of the same voltage available in standard wall sockets. This will be necessary in order to convert the power supplying your battery charger into the necessary type.
Step 3 - Construct an AC Charger
Use a silicon diode, a light bulb base, 16-gauge insulated wire and a connector to the inverter to create an AC-powered battery charger. Begin by cutting the wire into three pieces, two of about eight inches and one of 12 inches. Strip the insulation off the tips of each section of wire. Using a screwdriver, connect and wrap the end of one of the wire leads from the silicon diode to one of the base connectors of the light bulb base. Attach one end of one of the short wires to the other wire lead on the diode.
Next, connect the other short wire to the inverter on one end and to the other connector at the bottom of the light bulb base on the other end. Finally, fasten one end of the long wire to the other connector on the inverter. You may wish to mount all of the wiring and the light bulb base onto a surface or into a case of some kind to allow for greater portability. Screw a light bulb into the base.
With the inverter connected to the DC power supply, connect each of the open wires to one end of the battery to be charged. Secure them in place with tape. Allow for several hours for a standard-sized battery to charge fully, and beware of the possibility of overcharging. If you have any further questions, do not hesitate to consult with an electrical expert or hardware supply store.