Thread: PROJECT 2A, New Headlight wiring up grade

Originally posted by drivesafe


1) John, what does the voltage of the battery remaining at 12 volts got to do with the current load being caused by the filaments.

2) Again, using the starter motor as an example. Your vehicle’s battery drops to 8 and in some situations as low as 6 volts while cranking so of cause the battery is not going to remain at 12 volts. As I have already pointed out, the start up current draw is so high that it looks like a dead short at the alternator, when the power is taken directly at the alternator instead of at the battery. A dead short is a low voltage event.

3) The battery still acts as a current supply during the initial start up of the globes and as such cushions the high current draw before it gets to the alternator.

4) No matter what the voltage is or drops to, there is still going to be a huge current draw that is way WAY above what the alternator can produce. This high current draw means there is going to be a voltage drop and this is not what the alternator is designed to work against, it’s designed to try and maintain the voltage and it can’t do that when the current draw is far beyond it’s maximum capability, whereas the battery is specifically designed to caters for high current drains and the very reason everything is connected to the battery and not the alternator.

5) And once again, if this was a better way to wire a vehicle, I’m sure the makers would be doing so.

Cheers.

I seem to be expressing myself unclearly or something!

But looking at your points. (I'll do my best, but you try thinking straight with a five year old and a seven year old demanding explanations of what you are writing - they just got up!)

1) What I was trying to say is that the battery's electrochemical reaction in the battery still produces the same voltage even though the voltage at the terminals is a lot lower due to internal resistance. But its really irrelevant to my point that the startup current is a lot lower per filament with multiple lights because the battery voltage is lower.

2) A dead short is not an exact term, but implies that the resistance of the device is low compared to the wiring resistance. I have just measured the cold resistance of a bulb - the convenient one to measure was a 20w 24v bulb, which has a cold resistance of 3.5 Ohms. This implies a 100w 12v bulb will have a cold resistance of 0.35 Ohms, and an initial current of 35A at 12v. Even six of these would still only be 200A, and in practice less as the available voltage at the filament due to lowering of the battery voltage and resistance of the wiring would be probably eight volts at best, giving perhaps 150amps surge current. This is hardly a dead short, and in fact if your (single 100w lamp considered for clarity) circuit wiring resistance is of the order of 0.35 Ohms the voltage drop at normal current of over eight amps will be close to 3 volts - completely unacceptable - clearly our total wiring resistance must be way under this, so the cold resistance of the filament cannot be considered as a "dead short". If the wiring resistance is low enough for normal operation, then the cold filament resistance must still be high compared to the wiring resistance.

3) Certainly the battery supplies the current surge at startup - but it does this regardless of whether the power feed is taken from the battery or the alternator. The wire between the alternator output is normally the heaviest wire in the system apart from the starter wiring, and the voltage drop along it even at a surge current of several hundred amps will be much less than the drop due to the internal resistance of the battery.

4) As in 3) above - the alternator is not supplying this surge - the battery is, but since the two are connected by a heavy wire with very low resistance the drop across this is marginal and almost the same regardless of which end of the alternator feed the drain is from. The drop in battery voltage is just as large and still appears at the alternator.

5) As I said earlier, the manufacturer's wiring is designed mainly to make manufacture easy, just as long as the results are satisfactory (not best achievable). After all, if the manufacturer's wiring was the best possible, you would not be adding a relay which the manufacturer in their wisdom considered unnecessary.

One point should be noted that although getting the highest practical voltage to the lights will give the brightest light (and even very small increases in voltage make a marked increase in efficiency), operating tungsten filament bulbs at a higher voltage does decrease their life. As against that, note that my 1974 Citroen (which does have relays) still has all its original bulbs, so given good quality bulbs, the life is so long that even operated at a slightly higher voltage, bulb life should not be a problem.

Hi John, I don’t know how you arrive at some of you posts and I’m not going through it all again but consider this, if as you say,

Originally posted by JDNSW+--><div class='quotetop'>QUOTE(JDNSW)</div><div class='quotemain'>5) As I said earlier, the manufacturer's wiring is designed mainly to make manufacture easy, just as long as the results are satisfactory (not best achievable). After all, if the manufacturer's wiring was the best possible, you would not be adding a relay which the manufacturer in their wisdom considered unnecessary.[/b]

Why is it that just about every vehicle now made has headlight relays. If the manufacturers were still out to make a dollar the cheapest way they can, they would still be routing the power for the lights through the headlight switch.

To get the brightest lights they can, the manufactures have gone to extreme lengths, in modern vehicles to get the voltage at the headlights as high as practicable, via relays and better wire size and I don’t think anybody with a new vehicle is going to get any benefit from fitting any form of headlight wiring upgrade because, contrary to your suggestion, manufacturers do now look for the best achievable results.



<!--QuoteBegin-JDNSW
One point should be noted that although getting the highest practical voltage to the lights will give the brightest light (and even very small increases in voltage make a marked increase in efficiency), operating tungsten filament bulbs at a higher voltage does decrease their life. As against that, note that my 1974 Citroen (which does have relays) still has all its original bulbs, so given good quality bulbs, the life is so long that even operated at a slightly higher voltage, bulb life should not be a problem.[/quote]

I don’t know how on earth you can compere a globe from a 1974 vehicle to a modern globe.

All electrical gear going into vehicles today are marked as 12 volt or 24 volt.

I know of no so called 12 volt vehicle that runs at less than 13.5 volts, with the majority running at between 14 and 14.3 volts and the new D3s and RRSs being capable of supplying operating voltages of up to 15.7.

There for it should stand to reason that a 12 volt globe is actually designed to run at 14 volts and before you try to contradict this, go check the manufacturers specs for their 12 volt range of globes, you will see they have an optimum recommended operating voltage of 14 volts.

Now back to my argument, if there was a gain to be made by running ANYTHING of the alternator, the manufacturers would be, but they are not. Good enough for them, good enough for me.

Cheers

I am perfectly aware of the actual operating voltage of so-called 12v systems. I can compare the bulbs of 1974 for the simple reason that this whole discussion is about upgrading the wiring on Landrover vehicles that do not have relays in the lighting circuit. In fact, the topic heading is for the 2a, which ceased manufacture in 1973.

There have in fact been only minor improvements in tungsten filament bulbs since the introduction of quartz halogen bulbs almost forty years ago. Certainly high intensity discharge lights are a different discussion altogether, but these are used by relatively few cars, and none of the ones under discussion.

As you correctly state, today most manufacturers pay more attention to the quality of the lights than was the case in the quite recent past, and as you state, there are probably no manufacturers not using relays, although this may have more to do with the declining cost of relays than anything else in some cases.

John, the point I was trying to make is that not only have the globes improved but so have the vehicles and it’s a bit hard to try and compere things that are some many years apart.

But no matter what era you look at, manufactures do not use the alternator as the main supply and with the improvements occurring and the different makers all willing to exploit anything that may make their vehicle better than someone else’s, I’m sure if there was an advantage to using the alternator, they would.

If you wish to do it the way you have, by all means continue, but I will continue to advise my customers not to use the alternator as the main supply point over the battery.

Cheers.

mmmmm, yes I agree with both of you 8O , Drivesafe,let me know when the kits are ready, I'll take the easy way out as usual.

OK folks, I am just waiting for one more part and the kits will be ready ( HOPEFULLY be the end of the week ).

I’ve edited the first page and posted some info on using crimp terminals for those not use to how these are fitted.

Is there anything else that anybody would like posted or covered that they think could help fit a headlight kit to their vehicle.

Cheers

Originally Posted by JDNSW

Only problem I can see with this is my 2a and most of the others I have seen over the years, including two out of three my mobile parts supplies do not have H4 connectors on the existing headlights. My impression is that although the H4 connector is listed from suffix B on these were not fitted in Australia until the headlights moved into the mudguards in about 69. A lot of these may have been converted however - I have been thinking about converting mine, and probably put a relay in at the same time.

(I have no problems identifying wires etc, but others may have problems)

John

JD i think you may have confused Drivesafes "project 2A" with series 2A..... My understanding is that "Project 2A" is an upgrade to Project 2 - headlight wiring upgrade - its not ment to relate to what vehicle the setup is applicable for ---- i have to read it twice to figure it out!

either way - thanks Drivesafe for this excellent project

Mick

Hi Mick, if this is the case then maybe I should call it “ Project 2 Second addition “

Cheers.