Tuesday, October 7, 2014

All about shiny bright headlights!

This blog post is for educational purpose only to understand different types of automotive lights that are available in the market today. I am not recommending the usage of high powered bulbs. Those are illegal and a safety hazard.

Ever tried driving in the night on Indian roads? Ever felt the need for brighter headlamps? I am trying to put together all that I know about brighter lights based on my research.

It all starts with one person deciding to go against law. As per law in India, halogen light upto 60w per bulb are allowed to be used as headlamps on vehicles. But then,  more often than not, those tourist buses, cabbies and some private vehicles decide that 60w of lights is not enough and upgrade to 100w, 110w or even 130watts of halogen bulbs. That is what is blinding the oncoming traffic. Mind you, none of these lights are street legal - which means it is illegal to use them for driving on public roads.

Now, as a fellow user of the road, these blinding lights are a safety hazard for you. You will not be able to spot any obstructions (which are plentiful) on the roads, you may not be able to see the edge of the road. These lights also put tremendous strain on your eyes. No amount of flashing the lights will make the oncoming persons to use the dipper or low beam. That is when the insatiable urge to get even with equally or more powerful blinding lights play tricks on your mind :).

Broadly, there are three different types of lights available in the market today:

1. Halogen bulbs
2. HIDs
3. LED

1. Halogen Bulbs: 

Cars in India primarily come with different types of halogen bulbs which are marked as H4, H1, H7 etc. H4 type is most popular and comes with two filaments - one for low beam and another for high beam. The filament is tungsten and the bulb is filled with some type of halogen gas. Now, there are OEM direct replacement bulbs that provide upto 100% additional light for the same wattage. Which means, there is need to quantify the light produced.

Wattage is rough way of looking at brightness of the light, the actual way to measure is lumens. For eg, a standard 100w bulb will provide 1500 lumens of light. Ideally, we would like 1:1 mapping in terms of wattage and lumens which would be 100% efficiency. So, the bulb is operating at 15% efficiency which means, the remaining 85% is dissipated as heat. So roughly a normal 60w bulb would produce 900 lumens of light. Some brands like Philips Xtreme Vision use a different gas to charge which has better efficiency and for the same wattage ie 60, it will produce higher lumens - not sure about the exact amount though - due to which it produces more light. Since the wattage is same, it is safe to use as direct replacement for original bulb.

Now, if one is upgrading to 100w bulb, then, following things would occur:

W= VA. Circuit is designed by original car maker for 60w. So W=60. V is constant from your battery = 12v. So, for a 60w bulb operation, the A would be w/v = 60/12 = 5Amps. Now, if you replace 60w bulb with 100w, then A would be 100/12=8.5 A. Combine this with the efficiency of the bulb which I mentioned above. This leads to two problems:

a. More current flowing through the circuit, overloads the wiring and will lead to melting of insulation of wires again leading to short circuit.
b. Excessive heat generated due to high wattage bulbs. So the plastic holder designed for 60w melts and leads to short circuit.

So, if one is to upgrade to higher wattage, appropriate wiring kit that includes a relay and ceramic holders is required. The entire setup will cost around 2000 Rs including bulbs. If the bulbs are of higher wattage than 100w, then there is a serious risk of the plastic reflectors turning black in the headlamp assembly. Mind you, the bulbs dont last as long as the 60w ones as well.

2. HID

We need to understand three things here:
a. Project headlamps
b. HID upgrade kits
c. Bulb types

HIDs are primarily to be used only in a projector setup. HIDs are street legal upto 35w IN PROPER SETUP. There are some cars that have reflectors that are specifically designed for HID bulbs but then, most of the cars are not. Before we get into other things here, we need to understand how the HID bulbs work. In a traditional halogen bulb, the tungsten filament lights up to provide the light. In a HID, there are some super duper expensive salts (some iodides) which create an arc when HIGH voltage is passed through them. How much voltage? probably around 25000 volts. Yes, you read it right, around 25KV for the initial arcing to happen. So when you switch on the headlights, around that much voltage flows through the bulb to create the light arc but then, once arc is created, it requires lower voltage to sustain around 42V. Remember, your car battery is 12v. So, that is where a ballast comes into picture. Ballast is essentially a step up transformer (intelligent one) which provides that kind of voltage for the arc to happen and to sustain. So, by now, you would have realized, HID is not just about plug and play of HID bulbs. The main component is the ballast and the entire setup will cost around 12000/- rs. Each bulb will be in the range of 3000 Rs. Now, for intelligent cars that display that one of your lights have gone kaput in MID, need something called canbus ballast which is generally costlier. There are cheaper HID kits in the market but they are not durable.

So with that theory, let's get started with the projector headlamps. The HID bulbs scatter light in all directions ie 360*. So to prevent glare and provide the focus for the headlight, projector lenses are used which is what gives that cool look to headlights, like the ones that are available in BMWs, Mercs and other high end cars and now, in the likes of TATA ZEST, XUV500 as well.

The HIDs produce different colors and is what is denoted by the 6000K, 4300K, 8000K marking. The light is red/yellow in the lower bands like 4300K and become whiter at 6000K and at 13000K it is purple. The most suitable for driving are 4300K and 6000K. Others are fancy color lights - thats about it.

Now, the projector setup comes with expensive cars and after market projectors is difficult to source as different cars have different headlight shapes.

That is where the HID conversion kits come into picture. What that does it gives you a way to fit HIDs into your existing reflector headlights. By now, you have realized that it involves additional wiring for ballast and the HID bulb will throw light is all directions. Most likely you will not be happy with the focus after the installation - so it requires a good skill have it focused right. Also remeber, 35w of HID light is almost 2200 lumens which means, it is brighter than 110w halogen bulb. So, with a better conversion efficiency, the bulb tends to heat less, and less damage to headlight assembly. However, note that the initial arc requires 25000 volts that puts tremendous stress on the circuit. So that is why, you see most cars that use HIDs use it as low beam - once the lights are on, it stays on. High beams require switch off and switch on operation which makes high beam not so suited for HIDs. This, in the 4 lamp setup with 2 low beams and 2 high beams. There is no concept of low beam filament and high beam filament in H4 HIDs so they are called bi xenons which is trick used to provide high and low beam with a cover that moves in front of the xenon bulb when you switch from low to high and vice versa.

Finally, the HID bulbs are marked as D4R and D4S which specify the usage. D4R stands for reflectors and D4S stands for Straight (projectors). D4R has some glare removing at the front end of the bulb where as D4S does not. D4S should not be used in reflectors. D4R is for use in reflectors that are specifically designed for xenon - example 2010 Toyota Corolla GL model. It is another matter that corolla xenon bulb costs around 10500 Rs per bulb, yes you heard it right, in dealerships.

3. LED

This is the newest trend and does not require any kind of ballast for wiring. The efficiency is also slightly better than HID - at around 27W delivering around 2200 lumens. But, the challenge is to find the right fitment to your reflectors. Also, although LEDs have better efficiency and generate less heat, the LEDs are susceptible to the heat generated by them which is far less than the normal halogens. So, some LEDs come with cooling fans that particularly pose a challenge to direct fitment. If you find a good LED bulb that fits your car type, then if you go upto designed wattage, you will get some serious bright light. For eg. a 45w LED can throw around 4000 Lumens. Probably that would be too bright for your eyes to drive, let alone the one coming from the opposite side.

Hope this post helps clarify the doubts that you have in your mind about headlamps.

Disclaimer: All the above information I have published based on my research and please use discretion before you decide to take the plunge. Please note the usage of higher wattage bulbs is illegal. Even the auxiliary lamps are illegal for street use and should be used for off road purpose only.

- Aravind