Off-road vehicles are driven in wetlands and swamps, in the environment of large temperature difference, high humidity and high amplitude for a long time, often encounter with the bad weather of strong wind and waves, and have high requirements for the reliability and stability of lighting equipment. Therefore, it is very important to choose a high quality light bar suitable for your car.As to how to choose the right light bar for your car, here are some criteria that you can use as a reference when choosing a light bar.1.SizeThe size of the light bar is a very important factor you must consider. Length is important because you need to make sure the LED light bar you buy fits your truck. Measure where you want to install, and then purchase suitbale LED light.2.AppearanceThe light bar is mainly divided into straight one and curved one, which are also divided into single row, double rows and three rows.3.Light patternLight pattern refers to the angle of the beam. This is of great significance because off-road paths are often surrounded by obstacles, such as rocks or bushes. Both spotlight and floodlight modes work well for lighting, and you can install Led light bars of both modes at the same time to better illuminate both sides of the road and reduce the risk of bumping into something at night.4.Power/brightnessNow, brightness is actually measured in lumens, which is essentially the amount of light emitted at the time. Obviously, the higher the lumens, the stronger the light. Since we're talking about off-road, you'll definitely need a high lumen light bar. Some of the brightest LED light bars range in brightness from 30,000 lumens to 50,000 lumens. This range allows you to really light up dark paths, especially at night.5.Water resistanceA better waterproof light bar will have a longer service life. Most light bars are IP67, better ones are IP68, while the difference between them is how submerged they are in water. Why do LED light bars need a relay?What is a relay?Relay is an electronic control device, it has a control system (also known as the input loop) and controlled system (also known as the output loop), usually used in automatic control circuit, it is actually an "automatic switch" which uses a smaller current to control the larger current. Therefore, it plays the role of automatic adjustment, safety protection and conversion circuit in the circuit.Working principle and characteristics of electromagnetic relay:Electromagnetic relay generally consists of iron core, coil, armature, contact reed and so on.As long as a certain voltage is applied to both ends of the coil, a certain current will flow through the coil, resulting in electromagnetic effect, and the armature will overcome the pull force of the return spring to attract the core under the electromagnetic attraction, so as to drive the movable contact and the static contact(normally open contact) of the armature for suction and close.When the coil is power off, electromagnetic suction also disappears, the armature will return to the original position in the spring reaction force, causing the moving contact and the original static contact (normally closed contact) for suction and close. Such suction, release, achieves the conduction and cut-off in the circuit. Function of relayLeds won't work without relays. Relays are vey important for bright lights. This is why relays are used when making LED lights.Without a relay, the control switch will not be able to handle the current from the LED light. When you have a low-power LED light, this is not a problem. But if you have a larger power supply, this can be difficult due to the lack of large switches. Without a relay, too much voltage or current passes through the switch, long-time overheating will cause the wires to melt.The switch can be cooled by using relays. When you do not use relays, some hazards are easy to occur.What relay for LED light bar?Understand the necessary conditions:①The power supply voltage of control circuit , the maximum current it can provide;② Voltage and current in the controlled circuit;③How many sets and what form of contacts does the controlled circuit require Generally, the power supply voltage of control circuit can be used as the basis to select the relay. The control circuit should be able to provide enough working current for the relay, otherwise the suction and close of relay will be unstable. When confirming the working condition by consulting the relevant information, you can look up the relevant information to find out the type and specification number of the relay you need. If you already have relays in hand, you could check whether they can be used according to the data. Finally, consider whether the size is appropriate or not.How to wire led light bar without relay?People can connect LED light bars without relays. But that is not a good idea. If you are not sure whether switches, fuses, and wires are the right size for amps, then you should use relays to avoid bad things happening. You can install the LED light bar without relays if you are sure that everything is appropriate and no danger will happen.1.The first step is to determine the installation position of the light bar. Drill several holes of the right size in the chosen location. Before drilling, be careful not to touch anything that will be damaged by the drilling.2.Next, wrap a wire around the screw on the back of the LED bar, with one end sticking out just long enough. The parts that come out are mostly hidden. Then take another wireand wrap it around another screw on the back of the LED bar, allowing one end to stick out.3.Put the LED barin the appropriate position. Align the screws with the drilled holes. Be careful not to tighten them too tight at the moment, as you may need to adjust the angle or position later in the process.4.Locate the power side of the battery and determine the direction of the switch. Go to the place you want to put the switch and drill a hole. The size of the hole should match your switch. Connect the wire to the switch and put it in. You can also use a remote switch to avoid this step. 5.Connect the car wire to the negative terminalof Then connect another wire from your car to the positive terminal of battery.6.After this process is complete, adjust the installed light bar to the desired direction and angle and tighten the installed parts.