How to Run LED Lights From a 12v Battery
LED lights are a popular way of saving money in the home. They last for many hours, and a gently used light can last up to 25 years. Most LED lights are arranged so that they can run off of a 12v battery—in fact, 12v lights can cause a short when plugged directly into a socket, which usually have 110v current. This can be very dangerous, and so the best solution is to run these lights through a relay instead.
Step 1 - Decide Where to Put It
The first thing that needs to be done when connecting LEDs to a battery is to consider where they will go. Batteries operating lights on a high wall, for example, will need to have something supporting their weight. Unless you are installing these near an existing 12v battery supply, prepare to build a ledge, box, or other support. Leaving a battery to dangle will eventually cause connections to break.
Locate a nearby place to put the battery and on/off switch; then, measure the distance between where the lights are and where these will be. This is the length of wire necessary to connect the LEDs to the power supply.
Batteries and switches should be checked for faults before being wired to the LED home lighting system. This can be done by checking the current with a voltmeter, or by wiring both items to a lamp or device which is known to work.
Step 2 - Wire the LED to the Battery
Once the LEDs are in position, examine them and find the leads; the negative lead (or cathode), can be identified in one, or more than one, of these ways: it is the shorter lead, it is a flattened section on a round LED, or inside the LED, each lead is attached to a triangle-shaped node; the positive lead (or anode) is attached to a larger node. A diode test function meter will light up the LED when correctly applied. When it is lit, the black test lead will be attached to the cathode, and the red test lead will be attached to the anode.
When you are sure which lead goes to which, it is time to solder the wires to the 12v battery. The cathode goes into the ground—it can be soldered directly to the negative port of the 12v battery. The anode should be wired into the on/off switch, which is then wired into the positive port of the battery.
At this point, it is a good idea to check that the home lighting system works. Problems may include a blown fuse or damaged LED (easily done during wiring), or a loose connection somewhere between the lights and the battery. Correcting these problems is a simple task, and if the home lighting system is wired correctly, there should be no problems in using it for the foreseeable future.