Headlights Revisited

[JohnEd]

Brian -

Dina already uses relays for pretty much all of the lighting in my bus including the headlights.

Look at that - we've been suggesting relays, and the factory beat us to it!

That isn't a win for the factory.  He said the wires to the lights is too small so the stock "system" isn't good as is.

No matter what is in there, before you install relays or whatever, you must measure the voltage "AT" the bulb to determine success.  Remember,  no more than 1% drop.

John

[JohnEd]

Dina uses two headlights per side.  There is at minimum 7 more feet of wire over to the right headlight.  I do not intend to replace the high beams since they provide enough light when they can be used and they aren't used all that much anyhow.

I'm still not 100% sure what bulbs to use.  Daniel Stern is recommending Osram 70/65W bulbs that sell for $22 each since I have relays and the reflectors aren't that big.  Others are recommending the Osram Night Breaker Plus bulbs that are new and are 60/55W.  I can buy a pair for Night Breakers for what one 70/65W bulb costs.  There aren't many good H4 bulbs over 60/55W because Europe only allows up to 55W.  I am leaning towards the Night Breaker Plus bulbs based on the good reviews.

I would tend to take Daniel Stern's advice on just about anything related to lighting.  Whatever his flaws....stupid ain't one of them.

2 cents,


John

[belfert]

I went out to the bus today and measured voltages with all lights on.  All voltages measured with engine at idle.  Increasing the engine RPM didn't seem to change voltages.

Voltage at low beam headlight: 12.4 volts (Measured at left light.  Probably worse at right light)
12 volt voltage at front electrical panel: 13.2 volts
12 volt voltage at Vanner in rear: 13.7 volts
24 volt voltage at front electrical panel: 27.0 volts
24 volt voltage at batteries: 27.2 volts

Is my voltage at the batteries high enough?  Shouldn't it be a bit more than 27.2?

Obviously my voltage at the headlights is really bad.  I'm also dropping quite a bit on the 12 volt side at the front electrical panel.  The wire that runs all 12 volt power from the Vanner to the front is only like 6 AWG so that is probably why I am losing half a volt.

I need to install relays at the headlights for sure.  The factory relays on the front electrical panel aren't cutting it.  I will probably run my headlight power all the way from the battery to get good power.  I will need 8 or 10 AWG wire to deliver the nearly 24 amps needed at high beam with no voltage loss.

[JohnEd]

Belfert,

Use that formula for computing wire gauge requirements.....6AWG might be enuf. ?  Consider just adding a wire to the 6AWG in parallel to achieve the desired voltage drop.

I would prefer to increase the wire size/connectors/terminal posts  whatever, and correct the loss in the 12 volts running to the front panel.  Use the panel for the 12 volts that power the lights through the new relays.  I would want to be getting maximum 12 volts to everything being powered.

You aren't having problems with the formulas and logic for computing the wire size are you.  I think that is probably simple for you but I can't be sure.  I will run the numbers for you if need be.

John

[belfert]

I think trying to replace the main 12 volt feed from the rear to the front electrical panel would be a nightmare.  The electrical panel is up over the driver's head.  All of the wires pass through a channel on the inside of the windshield pillar that is full.  It would be easier just to run new wires to the headlights.

I'm not really sure what the ideal voltage drop is.  Some say 2%.  2% of 13.7 volts at the Vanner is .274 volts.  For my 27.2 volts at the battery that would be .544 volts.  Currently, my 24 volt drop is only .2 volts so I am good there.  My 12 volt drop is .5 so that is probably too much.

Daniel Stern's site says the Europeans consider full voltage for headlights to be 13.2 volts.  I am well below that as it sits.

The size of wire required to handle 13.7 volts at 22 amps over 30 feet is huge!  I would need 2 AWG to keep loss to 2%.

[JohnEd]

I would give a lot of consideration to using the body for the return.  With good conections it should be a perfect zero drop. Do you know how to test that theory?

You look to have this thing on a down hill drag....good work.

John