# Amp draw during HID startup



## Xzn (Dec 27, 2006)

Was surfing around youtube looking at HID projects and ran into this... intereresting.

http://www.youtube.com/watch?v=NCqjSLUIkjk


----------



## Ra (Dec 27, 2006)

Many ballasts have this current-curve to bring the lamp to full output much earlier. It always takes much energy to evaporate the internal ingredients. But you can go too far doing this: Too much current evaporates the electrodes a bit, very much shortening your bulblife !!!!

The laws of nature determine how fast you can evaporate the ingredients without evaporating the electrodes !!!


Regards,

Ra.


----------



## wulfgang (Dec 27, 2006)

The warm-up time of the automotive xenons is regulated so that they reach 75% of output in less than 2 seconds (SAE J2009). However, although the current during the warm-up is large (maybe 4x the steady-state current), the power delivered to the bulb is roughly constant since the warm-up voltage is so low.

Since most, if not all, of these flashlight designers use ballasts that were designed for automotive use, they inherit the fast startup times and high initial current draw.


----------



## Nereus (Dec 28, 2006)

I have been playing with a automotive 35w hid unit. It takes over 100w during the first few seconds after turn-on. After 10 secs it has settled down to steady state current.

-N


----------



## wulfgang (Dec 28, 2006)

You're right... I must've been thinking p=ir instead of i^2 r.


----------

