| Author | Message | ||
| Ken Smith/Theresa Herring (Bikerider103152)
Registered Member Username: Bikerider103152 Post Number: 12 Registered: 7-2009 Posted From: 64.25.202.134 Rating: N/A |
2 yrs ago I purchased my first bus, 1965 MCI A. Since then I have been working on some things that needed updating and am coming along nicely on it.Got to take its longest trip this month, all went well and I was extremly happy with the 10mpg I got on the 3oo mile trip. Well back to volt question. I am pretty mechanicly inclined however not real sharp on electric issues. Question is can someone tell me how my bus converts 24 volt system to 12 volts. Is it done through resistors? | ||
| Derrick Thomas (Thomasinnv)
Registered Member Username: Thomasinnv Post Number: 23 Registered: 10-2010 Posted From: 72.171.0.140  Rating: N/A |
there were 2 oem options. The first option was to tap off the center post between the two batteries for 12 volt accessories. The easiest and cheapest by far, but the problem with this method is the 2 batteries are always being charged/discharged un-evenly. the second option was to use a vanner. a box that is connected to the posotive post of both batteries (one gives 12v the other 24v) and the ground. This method ensures even charge/discharge of both batteries. Vanners can be little spendy, but then so are the 8D's if they are abused. | ||
| Jack Fids (Jack_fids)
Registered Member Username: Jack_fids Post Number: 835 Registered: 1-2009 Posted From: 72.211.145.15  Rating: N/A |
WOW! THE definitive answer on the first reply! ...and with only 23 contributions to our ( Ian's ) forum... It kind of makes you a mountain in comparison to Laffy-Ah's whining gopher hole history. You are Da-Man, Derrick..! | ||
| Brandon M (Brandon314159)
Registered Member Username: Brandon314159 Post Number: 25 Registered: 3-2011 Posted From: 12.108.0.2  Rating: N/A |
Stay away from offset battery charge/discharge. I had a couple group 31 batteries in my Unimog go unbalanced (one boiled, the other mildly discharged) while charging and things got real unhappy. This was all caused by a 1.5A load (ham radio). I now run a 24 to 12V converter @ 30A. Works good! | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 1474 Registered: 3-2007 Posted From: 76.4.118.153  Rating: N/A |
MCI Has a wiring diagram for this set-up and it is good! Check the archives for it as I don't remember were it be hiding at LOL Gomer | ||
| Ken Smith/Theresa Herring (Bikerider103152)
Registered Member Username: Bikerider103152 Post Number: 13 Registered: 7-2009 Posted From: 64.25.202.134 Rating: N/A |
Thanks for the replys to everyone. Like I stated I am not very electrical minded. I will have to check and see which way my bus is set up. I just could not understand how it was changing from the 24volts to 12 for lights and insturments,etc. thanks again to all. | ||
| Brian Evans (Bevans6)
Registered Member Username: Bevans6 Post Number: 53 Registered: 5-2009 Posted From: 65.92.54.193 Rating: N/A |
MC-5A, unless it is modified from stock, doesn't use 12 volts for anything. All lights, instruments, accessories are 24 volt. It does have a 12 volt supply available on stud 55 in the main electrical box and stud 6 in the air conditioning electical box, either a direct tap off the center battery post or with a Vanner installed as stock, but the bus itself doesn't use 12 volts. It's there to facilitate the installation of things like ticket machines, radios, etc. Those stud numbers are from my 5C manual, but I've found that MCI didn't change things between models much so they may be right for you. The 12 volt feed has a 10 amp fuse, mine is located at the top right hand corner of the battery bay. If your bus is using 12 volt for lots of stuff, then you have to figure it out, the wiring won't be standard or in a manual. Brian | ||
| Brian Evans (Bevans6)
Registered Member Username: Bevans6 Post Number: 54 Registered: 5-2009 Posted From: 65.92.54.193 Rating: N/A |
sorry, need to edit a bit and I don't know how to edit on the board... The stock MCI 12 volt feed is a 10 Gauge wire, and the fuse is a 30 amp fuse... | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1192 Registered: 8-2006 Posted From: 74.33.48.167 Rating: N/A |
GreyHound ran the center tap on their buses for lighting seems to work ok for them good luck | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1259 Registered: 8-2006 Posted From: 99.37.28.23 Rating: N/A |
Ken, Brian and Derrick have it right. If you hook on to the center connection between the batteries, you will get 12 Volts to ground. The problem is that all the current you are using has to come through the other battery, which is already fully charged. Consequently the other battery is over-charged by the amount of 12 Volt current you use, period. Greyhound does NOT use 12V off of one battery either. There is a properly working schematic in the archives for true center tapped 12 Volt headlights, which does not abuse batteries, or cause total darkness when one bulb burns out. Other than that, a Vanner, or somebody else's equalizer is the answer. Another answer is a 12 Volt alternator for your house batteries. G | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 1476 Registered: 3-2007 Posted From: 76.4.118.153 Rating: N/A |
Georg I have tried to find the wiring diagram from MCI in the archives and I can't find it.I know it has been brought up before and it came up with the MCI factory wiring. Gomer | ||
| Brian Evans (Bevans6)
Registered Member Username: Bevans6 Post Number: 55 Registered: 5-2009 Posted From: 65.92.54.193 Rating: N/A |
True center tapped 12 volt headlights use a line from 24 volts to the 12 volt tap for one pair of headlights (those ones don't have a ground connection) and center tapped 12 volts to ground for the other pair of headlights. If a light burns out, the other one still runs but there is a temporary (until you fix the light) charging imbalance. With both lights on the load is equal to the batteries, more or less (headlights will have to be matched nominally, same wattage for each side, and since there will be some difference of a very minor sort, there will be some difference in load) Anyway, that's center tapped headlights for 12 volt lamps in a 24 volt system that works fine. Brian | ||
| George M. Todd (George_todd)
Registered Member Username: George_todd Post Number: 1261 Registered: 8-2006 Posted From: 99.37.28.23 Rating: N/A |
Gomer, Brian has it right again! It also sounds exactly like what I said here about three years ago, when we were discussing a 24 to 12 Volt headlight conversion. Its picky I admit, but the true center tap circuit doesn't care if one headlight is a couple of watts off the other, as each bulb is electrically connected across one battery. The beauty of this circuit is that you don't get total darkness when one bulb burns out while using two 12V bulbs in "series." 12 Volt headlights in true series don't give the correct light either, as the ground from one bulb can only be connected to either the high or low filament of the other bulb, unless a double-throw relay is added. The 12Volt MCI schematic for this was posted here at that time, and is incredibly complicated. It also doesn't work any better than the one I drew, and has a whole lot of diodes to keep the spike down when the relay coil circuit opens. I drew mine so that the spike dissipates thru the headlight bulbs, and its so small they don't notice. A Vanner is stock in most of the later MCIs. Anyhow, Ken gets points in my book for having the gumption to say he's not an electrician, instead of letting the smoke out of something! G | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 1477 Registered: 3-2007 Posted From: 76.4.118.153 Rating: N/A |
George I must have missed the diagram as I usually print them and file them away. LOL Gomer | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 2102 Registered: 12-2000 Posted From: 174.89.174.139  Rating: |
If you know how your home works in 120/240, with half the house on one side and the other half on the other side... Wiring 12 volt headlamps in a 24 volt system works the same way, treating the two batteries like your two hots that make 240, with the centre tap acting as the neutral. George's drawing from a couple years ago did a nice job for the busnut to follow. http://www.busnut.com/bbs/messages/233/24770.html?1231817819#POST131470 Scroll down to the picture posted by the Bossnut for George. happy coaching! buswarrior | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 1479 Registered: 3-2007 Posted From: 76.4.118.153 Rating: N/A |
Thanks BW I printed it again Gomer | ||
| Brice Abell (Babell2)
Registered Member Username: Babell2 Post Number: 27 Registered: 12-2010 Posted From: 72.145.162.191  Rating: N/A |
Back to the OP Look in your battery compartment if you see a flat box with wiring to both batteries that is your vanner and it does the 12 volt split for your systems. |
