12 volt headlight question

travelingfools · May 10, 2011, 09:19:17 PM

Im converting my headlights on my '87 MC 9 to 12v and my question is should I feed them off the 12v post on the vanner or off 1 battery ?

Chopper Scott · May 11, 2011, 04:58:51 AM

Feed one side of the lights off of one battery and feed the other side off the other battery. I don't know any short cuts other than adding another relay and running wiring. Someone else will chime in that knows more.

robertglines1 · May 11, 2011, 05:26:53 AM

not to be smarty but are you sure they are not 12 volt already? my 8 was. of course they could have had kit put in them by charter service it came from.So was my 89. If not might be worth just reducing voltage at headlight and leaving rest of switches etc 24 volts. jmho Bob

bevans6 · May 11, 2011, 06:32:31 AM

There are a number of different ways to skin this cat. My bus has MCI adaptor units installed that drop the voltage from 24 down to 12. On my list of things to do is investigate the actual voltages in and out - the lights aren't as bright as I think they should be.

A second way is to run the lights from 24 volts in series, so each drops half the voltage. Downside is if one light fails, the other fails too. Not the optimum. If you tie the center tap between the lights back to the center tap of the battery pair, then each light is again independent. I think this was a stock MCI solution at one point.

Some run the headlights from the house battery setup. Can be a good solution but you need to have the bus engine charging the house batteries for it to be a satisfactory method as far as I am concerned. I am pretty rigorous about fail-safeing and I feel that the headlights should be ultimately driven from the bus alternator/charging system.

Headlights typically draw 55 watts/65 watts for each low beam and 55 watts for each high beam. So you would have a draw of 240 watts with four bulbs on high. At a nominal 13.6 volts that is a little under 20 amps. On my MCI the 12 volt accessory feed is fused at 30 amps, so that is sufficient for the normal headlights if you don't use the stock 12 volt feed for anything else. It's also well within the Vanner's capability. If I were retrofitting this I probably would use a dedicated fused (breakered - is that a word?) feed from the Vanner for each pair of headlights, fed through relays.

Direct connect to the battery. If you have a Vanner, you can't actually do that, since the Vanner will equalize the voltages regardless of how you connect to the batteries. You could, obviously, not connect the Vanner, but why?

My optimum solution is to run the lights at 24 volts, install Hella's or the equivalent, and simply buy 24 volt H4 and H1 bulbs. By far the easiest and should be a great solution. I think Sean uses and recommends this solution.

Brian

belfert · May 11, 2011, 07:33:17 AM

I am doing 24 volt headlights as Brian suggests. I actually did the opposite of what the OP wants to do. I have 12 volt sealed beam headlights now and I am converting to 24 volt.

I bought Cibie headlights and I will be running 24 volt bulbs. I bought 2 pairs of 24 volt bulbs so I have a backup pair of bulbs. Over the years I have had my bus I have never burned out a headlight knock on wood. I have replaced two lights due to water getting inside, but they still worked. I don't think 24 volt bulbs are as rare as folks seem to think, but you won't get one at Walmart. NAPA stocks or can get 24 volt bulbs.

Lin · May 11, 2011, 09:08:01 AM

First, I thought that the general purpose of the Vanner equalizer was to keep the batteries balanced in situations like this when you are drawing 12v from a center tap. Do I have that wrong? Second, why bother changing to 12v? If it is just a matter of bulb availability, keeping spares is cheap enough.

bevans6 · May 11, 2011, 09:11:28 AM

No, that's exactly what the Vanner is for and the anticipated load is well within the range of the usual Vanner model you find in a bus. There's just other ways to get to the end point besides using the Vanner, which doesn't make using the Vanner a bad idea.

Brian

glang · May 11, 2011, 12:08:09 PM

I have run my 12 Volt headlights off my house batteries (24volt) and a 100 amp equalizer for ten years.My House batteries are charging through the bus alternator (24 Volt 175 AMP) when the engine is running. Very simple way to run standard 12 volt lights on a 24 Volt bus system.

travelingfools · May 13, 2011, 07:28:14 AM

Completed the headlight project last night and took the ole' girl for a test spin and a little fuel. The results were well worth the efforts. My old headlights were awful and had a lot of "gremlins". I now no longer will feel the need to schedule all my trips during the daylight hours.lol. Thanks for all the opinions !

Busted Knuckle · May 13, 2011, 07:57:04 AM

Quote from: travelingfools on May 13, 2011, 07:28:14 AM
Completed the headlight project last night and took the ole' girl for a test spin and a little fuel. The results were well worth the efforts. My old headlights were awful and had a lot of "gremlins". I now no longer will feel the need to schedule all my trips during the daylight hours.lol. Thanks for all the opinions !

So please don't be a tease and tell us how ya did it! (pics would be nice too!)

BK

travelingfools · May 15, 2011, 06:36:14 PM

Sorry for the delay... Its been a crazy weekend. We figured out the amperage draw for the bulbs and came up with an 8ga wire off the vanner to a 3 way switch on the dash, then 12ga to the bulbs. The drivers side had a million splices in the headlight assembly, so the only thing we used there was the plugs that go into the bulbs. On the pas side we were able to splice in behind the "wall" using the orig harness and didn't half to disturb the grommet. We put 4 new halogen bulbs in and have awesome headlights for once.