I know this is an old thread but it is still relevant today.
I have a few thoughts on this whole dim H4 headlight problem. My night vision is not the best so I need to get this sorted - no carrot comments please!
In reply to Mooncats post -
Voltage across the lamp is all we are interested in as that determines how bright the lamp is. The system voltage minus the voltage accross the lamp is the total voltage drop. This is the total in the supply and ground parts of the circuit. Doing them separately is only useful to help locate the cause of the drops.
What do you mean by "remaining available voltage"? I am familiar with electrics and electronics.
However voltage drop is only part of the problem. The alternator doesn't give out a constant voltage. Try driving in 2nd gear at fairly high revs with the heater fan on high speed. If you are staying at a steady speed or accelerating then take your foot off the accelerator you will hear the fan speed up even though the revs stay the same or are reducing. This is to save fuel by keeping the voltage low and raising it when using engine breaking. A watered down version of regenerative braking.
Vans with H4 headlights have a combination of 4 problems -
1 - H4 lamps are always going to be a poor compromise as they have to do high beam and dipped beam.
2 - Poor reflectors due to having to do high and dipped beams.
3 - Low system voltage.
4 - Thin wiring for the lamps.
What are the options to rectify the problems of our budget headlights for improved light output?
1 - Swap out the crap for modern LED headlights, rewire and code as required. By far the best solution but unfortunately this is not an option for plebs like me who have to drive leased works vans due to the cost.
2 - Swap out the crap for H7 headlights. They are more affordable and should give a good improvement if you can get them cheap enough. Probably the best option for most people but I think some rewiring is also required.
3 - Add spot lights. A good cheap option until you need to use dipped lights which is most of the time for me.
4 - Run with your fog lights on all the time at night. A pet hate of mine as they dazzle everyone else and I think it is illegal. Also no use when on high beam. Not an option for my fog lightless bottom of the range van - my company knows how to make me feel valued!
5 - Fit 100 watt lamps. No good as the crap wiring and low voltage mean they stay just as dim and they're illegal.
6 - Fit LED lamps. Usually not a good option due to poor quality and the light not being focused properly causing oncoming traffic to be dazzled and they're probably all illegal.
7 - Make modifications to give a stable high voltage and use thicker cables. This is the route I intend to go down. I have bought a pair of 30A DC to DC boost converters, a fused relay box, an aluminium project box, a pair of H4 ceramic connector extension cables and a pair of 100w lamps. Total cost around £90. I could have done it for much less but safety is paramount here. I hope to get away with using Osram night breaker lamps, that I am using now, instead of the 100w lamps, to keep me legal.
If all goes well I will start a new thread explaining how I did it and maybe a before and after comparison. I want it to be safe and keep both headlights as two separate circuits so that a single fault is less likely to stop both headlights working. I also want it to be easily removed as the van is likely to be changed next year and also to allow everything to be easily bypassed if there is a fault. The original connectors will just need reconnecting back on to the lamps in an emergency. I may need to do some coding but hopefully that is not a problem. Choosing the best lamp and voltage combination for light output verses lamp life and dazzle, could be a challenge which will need some research. Even 24v 75/70w Osram truckstar Pro lamps (which I think are E marked) also become a possibility, in fact, anything up to 97v can be used but the lamps would need changing back to 12v lamps if something goes wrong.
This website has a tool to help see how voltage affects lamp life and light output -
www.ushio.com
It seems to only work in whole numbers making it is too course for 13.2v so I set it to 132v which gave better results but I don't know how accurate they are then. Raising the voltage to 13.8v gives 15% more light but halves the lamp life, which means Night breaker laser lamps average around only 80 hours on high beam, 200 hours on dip or a combination of the two. Still should last me a year or two so I will probably start around 13.8 to 14.0v.
If anyone has comments/criticisms/suggestions they would be appreciated especially before I start my modification in a week or two.
