How many lumen do A LED Car Headlight Bulbs Really Have?
There are so many different led headlight conversion kits on the market; we are hard to decide which one is better. But all of them will specify the Lumen output on the packing; normally they would be 4000 Lumen, 5000 Lumen, or 6000 Lumen. 6000 Lumen is extremely bright as we know. But we still can find some led car headlights bulbs marked with 8000 Lumen, 10000 Lumen or even 12000 Lumen. That is really unbelievable.
In order to find out who is lying, we gotta understand what Lumen is first.
The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total quantity of visible light emitted by a source.
We measure the lumen of a led headlight kit within a device named the integrating sphere. A bulb is positioned in the sphere and the light given off by the bulb is scattered by the inside of the integrating sphere and evenly distributed 360 all angles. The total lumen amount of a source of light could be measured accurately since light could be captured from all angles in the sphere.
But when the suppliers claim the Lumen of their led headlight, they don’t really mean their headlight can have this Lumen amount when measured in the integrating sphere, but just a theoretical peak Lumen amount. How to explain this, for example, 1W CSP LED can emit 130 Lumen output at most according to LED specification, if their headlight bulb has 16 piece of LEDs, they will claim that this led headlight bulb has 16W working power and 2080 Lumen, a pair of led headlight bulbs will have 4000 Lumen. But, it is just a theoretical peak Lumen amount.
In actual use, LED headlight Luminous efficiency is restricted by many subjective and objective factors and can’t reach the peak. Led bulb size, heat radiating area, working temperature, they will all affect and reduce the LED Luminous efficiency. A pair led headlight bulbs claimed 4000 Lumen; finally is possible to have 2600 lumen only.
But when the led headlight bulbs keep working for 5-15 minutes, we will notice that the lumen amount of led headlight bulbs are going to be stable ; only slightly move up and down but won’t continue to reduce quickly.
That is because, when led headlight bulb begins to work, LEDs will produce heat and make the light bulb be hot gradually, as the temperature on light bulb rising up, Lumen amount would reduce gradually until it reaches thermal equilibrium. Then working temperature won’t continue to rise up, heat radiating area is fixed, now, the Lumen output is the stability Lumen value, it is the true Lumen output of this led headlight and can keep working at this value for hours. Most of products on the market reach thermal equilibrium after working for 5-15 minutes. The better product structure design, the smaller gap between the peak Lumen value and the stability Lumen value.
We present the peak Lumen value too on the product pages of website, not the stability Lumen amount, that is because all companies in this industry do in this way, if we publish the stability value alone, we are easy to be washed out from competition without opportunity to explain to clients why our Lumen is lower than others. So today, we are publishing this post, what we wanna explain to you is, the stability Lumen output is the true brightness of automotive led headlight bulbs.