Due to its dimmer output, extra-low voltage (ELV) lighting's expansive range of use is typically found in applications like fish tanks, garden patios, holiday decorations and number plate bulbs. For some of the same reasons, 12-volt lights -- on the lower end of the less-than-50-volt ELV classification -- are ideal for hobbyists, from tinkering with homemade rockets to building train sets. Wiring lights to operate off of a 12-volt battery is actually quite simple, whether you're lighting a patio or a model.
Determine the length of wire needed. The length of wire needed for your project depends on your needs. If, for example, you are creating 12-volt lighting for a model rocketry set-up, you will need at least 25 feet between the battery, the switch and the lighting to maintain some distance. Lighting for other, more innocuous projects requires considerably less wire. Determine the length of wire you will need based on your project, and measure accordingly.
Cut three segments of wire. Once the proper amount of wire has been determined, cut two sections of wire for the appropriate length. (For example, if you determine you need 25 feet of wire, cut two 25-foot segments for a total of 50 feet; these wires will be laid in parallel to create a circuit.) Also cut a third, smaller segment of up to 12 inches; this smaller segment will be used to connect the switch to the battery.
Strip one end of each wire segment. To prepare the wires for connection to the lights, strip the insulation off approximately one inch of one end of each wire segment (not including the shorter segment, which will later be used to install the switch).
Solder or tape the wire to the lights. Protruding from the rear of the 12-volt light assembly will be two prongs; affix one stripped wire end to each prong. If you are comfortable using a soldering iron, and the connection is to be permanent, solder the wires in place. If you are not comfortable using a soldering iron, or if the connection is to be temporary, simply tape the wire to the prong using electrical tape.
Connect one wire directly to the battery terminal. Select one wire (with a direct current, or DC, connection; which wire you do this to is irrelevant) to connect to the battery. Strip approximately 1 inch of insulation from the loose end of the wire, and either solder or tape the bare wire into the small hole at the base of the battery terminal.
Connect the battery terminal to the battery. With the wire firmly attached to the battery terminal, slide the terminal over the negative (black) post of the 12-volt battery. Once the terminal is in place, tighten the terminal either with your fingers or, if available, a wrench.
Connect the other wire to the switch. Strip approximately 1 inch of insulation from the remaining loose wire end, and insert the exposed wire into the small hole on one prong of the switch. Either solder or tape the wire in place.
Connect the short wire to the switch and battery. Strip approximately 1 inch of insulation from each end of the remaining (short) wire. Connect one end of this wire to the switch as described in Step 3 above, and connect the other end to a battery terminal as described in Step 2 above. Place this battery terminal over the positive (red) battery post and tighten with your fingers or, if available, a wrench.
Turn the light on. Your 12-volt lights are now connected and should be operational. If your battery is charged, toggling or pressing the switch should illuminate the lights. Additional, optional steps such as grouping the wires or putting the switch and battery into a project box assembly may be taken to improve the appearance of your project.
If the lights appear dim or do not light, the battery may be weak; 12-volt batteries require periodic recharging. Additional, optional steps to improve the appearance of the project may include placing the battery and switch into a project box.
When the wires are connected to the battery, take care not to cross any sections of the wire; doing so may result in a short circuit, sparks and a potential fire hazard.