Voltage drop and headlight voltage

belfert · March 12, 2011, 09:01:03 PM

What percentage voltage drop do you folks consider acceptable? I've seen 2% written as an ideal, but boy does that require some large wires when going a long distance.

I am planning to run new wires from my batteries in front of my engine to my headlights. The distance is around 30 feet. To maintain a 2% loss at 22 amps for the headlights would require 2 AWG wire! The 2 AWG wire, relays, and other parts would cost more than the new Cibie headlights I plan to buy.

What would considered proper voltage for headlights? I read that Europe uses 13.2 volts as 100% for headlights.

I'm seriously considering running my headlights at 24 volts to reduce the amperage and required wire size. It would be a pain to run 2 AWG wire plus the 2 AWG wire would cost $100 more.

JohnEd · March 12, 2011, 10:47:47 PM

You just put your finger on why we went from 6 volts to 12 to 24 and I think 48 is on the way but that was only a rumor. You can still use 12 volt bulbs in series. You always have the "other" beam to limp to a rest stop. Phillips # 3 is all it takes.

And it is 1% if I am not mistaken. I got one percent every time but that was on a car run.

John

Gary '79 5C · March 13, 2011, 01:52:44 AM

Brian,

I would measure the voltage at the lamp socket, before doing anything. I do not know what the nominal headlight voltage is for your coach. If there is voltage drop, it could terminations which have been compromised with corrosion.

Just a thought, this is not the time to be purchasing large size copper wire....

belfert · March 13, 2011, 07:42:46 AM

I already measured the voltage at the lamp with the bus running and the lights on. I had posted my results to a different thread on headlights. Anyhow, I am only getting 12.4 volts at the headlight itself when the headlight is on and it should be around 13.2 volts if my research is correct.

I actually went out and measured the run from my battery compartment to my headlights just now. It is worse than I estimated and it is really 38 feet instead of 30 feet. I am thinking a 3% voltage drop is probably acceptable. This means I can use 8 AWG for 24 volt or 2 AWG for 12 volt. I used 4/0 cable for my 24 volt inverter because I got it dirt cheap from a friend plus it gives me less than a 2% voltage drop at a full 3000 watts.

If I go 24 volt from the batteries up to the headlights I think I will just buy 24 volt bulbs instead of doing them in series. If done in series with 12 volt bulbs if one bulb burns out you lose the other anyhow. I will carry a pair of spare bulbs in case of burnout.

Ericbsc · March 13, 2011, 10:25:13 AM

I was following this on another thread and mesuresd my voltage also. With lights on and engine off, I have 12.6v at the batteries and 10.3 at the pass. headlight. Not good I assume. I have an 05 eagle with the headlights froma 15. They are large retangular. I also noticed that even thought they look like they are sealed beam, I have water in them??? Also most of the reflective material inside the light has come off. I would like to upgrade but don't know if I need the eu lights or just relay mine from the front panel and get some bulbs that DO NOT CONTAIN WATER???

gus · March 13, 2011, 11:09:24 AM

belfert,

Your best bet is to find a terminal end of a heavy battery cable near the front, install a headlight relay (Or two generic cube relays) to it, and run the relay operating wire to the hi/lo beam switch.

Some buses have a heavy cable running to the front to operate the original bus AC/Heater air blower which is a huge motor. Find the blower motor and you will probably find the terminal.

There also is a heavy cable to the main electrical terminal box near the driver on GMCs, don't know about those foreign MCIs though!!

Eric,

There is always this problem with bulb headlights, I hate them. I've had the same water problem a couple of times, I call them goldfish bowls!

I found Halogen sealed beams at NAPA. They have a bulb inside the sealed beam, not just the filament like most sealed beams, so if the lens cracks they still work. They cost around $12 as I remember, it has been a few years since I got them. They are quite a bit brighter than sealed beams. I have one of each kind on opposite sides so it is easy to compare.

belfert · March 13, 2011, 11:26:07 AM

Voltage for headlights should be measured with the engine running. The alternator will supply more voltage than the batteries by themselves. You could start with relays and new sealed beams to see if that is enough before going all the way to ECE headlights. Sealed beams are cheap. I had water in at least one of my sealed beams and had to replace it.

As far as my bus, there are no heavy cables for motors going towards the front. Dina placed the heating and A/C blowers at the rear of the bus as far back as possible. All of that stuff is gone including wiring. The main electrical panel is above the driver. All of the wires go through a chase that is basically full. The voltage at the central panel for 12 volts isn't that great at only 13.2 volts anyhow. I am planning to install relays.

I'm trying to decide if I could install a 24 volt to 12 volt DC converter instead of runniing a huge wire back to the batteries.

JohnEd · March 13, 2011, 12:13:48 PM

Quote from: Ericbsc on March 13, 2011, 10:25:13 AM
I was following this on another thread and mesuresd my voltage also. With lights on and engine off, I have 12.6v at the batteries and 10.3 at the pass. headlight. Not good I assume. I have an 05 eagle with the headlights froma 15. They are large retangular. I also noticed that even thought they look like they are sealed beam, I have water in them??? Also most of the reflective material inside the light has come off. I would like to upgrade but don't know if I need the eu lights or just relay mine from the front panel and get some bulbs that DO NOT CONTAIN WATER???

You need "E" code headlights. They should be Cibies. If you can switch your bulbs to 7 inch round that would be a good move in terms of price and performance.

IMHO,

John

RJ · March 13, 2011, 12:22:30 PM

Eric -

If you have the 200mm (large) rectangular headlamps, Cibie makes a replacement. Less work than converting to rounds, albeit with slight illumination loss.

www.cibieusa.com

FWIW & HTH. . .

buswarrior · March 13, 2011, 03:47:48 PM

Excellent topic, belfert, and now I'm curious about mine....

A complete re-wire of the 24volt mess inherited was on the agenda.

Running the headlights on 24 volts per the MCI trick circuit with the centre tap for a burned bulb might help with your wire sizes for normal running?

happy coaching!
buswarrior

belfert · March 13, 2011, 05:13:52 PM

What I've decided to do is to run 24 volt bulbs in Cibie headlights. I have ordered two pairs of the Osram Truckstar bulbs someone here recommended. Yes, it will make my setup unique, but as long as I own the bus it shouldn't matter. I will put a label near the headlight switch to remind me the headlights are 24 volt.

I am planning to run a pair of wires directly to batteries. The run is 38 feet and will require 8 AWG wire for 24 volts at 11 amps to limit voltage drop. 12 volt wiring would have required 4 AWG wiring to handle the 18 amps. I can't imagine trying to run a 4 AWG wire back there as I had enough fun with some 10 AWG wires I ran for my trailer brake controller last year.

I will use relays or solenoids to control the headlights.

Tim Strommen · March 14, 2011, 01:50:22 PM

Quote from: Ericbsc on March 13, 2011, 10:25:13 AM...With lights on and engine off, I have 12.6v at the batteries and 10.3 at the pass...

That's not good, no... 10.3 / 12.6 = 81% or a 19% loss.

Quote from: Ericbsc on March 13, 2011, 10:25:13 AM......I also noticed that even thought they look like they are sealed beam, I have water in them??? Also most of the reflective material inside the light has come off...

You'll be happy to know that the Cibies have weep-holes in the bottom to drain condensation

.

-Tim

belfert · March 14, 2011, 04:40:56 PM

A friend encouraged me to recalculate the wire size required. Full load with headlights on high beam is 11 amps at 24 volts. I discovered if I dropped from 11 to 10 amps that the wire size dropped to 10 AWG. I don't use high beams all that much so I figure if I drop a little bit extra on high beam that it won't hurt.

10 AWG is so much easier to work with in many ways.

Tim Strommen · March 14, 2011, 11:17:22 PM

Quote from: belfert on March 14, 2011, 04:40:56 PM...Full load with headlights on high beam is 11 amps at 24 volts...
...I don't use high beams all that much so I figure if I drop a little bit extra on high beam that it won't hurt...

Using your train of thought, you'll have roughly 3-1/6% drop with both high beams and low beams (excluding switching and fusing), and 1.5% with just low-beams (again, excuding switching and fusing). You may find it closer to 2.5% and 5% when the relay and the fuse or circuit breaker is added in. I understand that cost and installation difficulty are your concerns, and I think that 5% is much better than say 20%...

...and it's probably much better than what you have now.

-Tim

belfert · March 15, 2011, 05:40:09 AM

I guess I ccan go with 8 AWG, but then I start to run into a lot more issues. The 8 AWG terminals/lugs I don't have anything to crimp them on with. I can crimp terminals onto 10 AWG wire all day long. I also don't like the fact that all of the auto reset breakers that handle 15 or 20 amps at 24 volts are only #10 terminals. I think the smaller terminals would introduce voltage loss.

I have attached a picture of an 8 AWG lug. What type of crimper do I use for that?