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Author Topic: 24 Volt System or 12 Volt System?  (Read 2525 times)
cpschevy
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« on: March 11, 2008, 09:38:27 PM »

I was wondering if anyone has switched there bus electrical system over to a  12 volt starter and alternator system? I know there is some solenoids and lots of relays to change but is there really that much else to change? I just don't like 24 volt systems, we changed our Big Bud 650 tractor over and it was simple. I figure all the lights are 12 volt anyway so why not simplify the system and make everything 12 volt.            Thanks for your help            Chris
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« Reply #1 on: March 11, 2008, 10:11:45 PM »

hmmm probably most of the wiring.

why would you want to do such a thing?

Are ya skeered of 24v
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cpschevy
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« Reply #2 on: March 11, 2008, 10:19:10 PM »

No not scared just dont see any reason to have both 12 volt and 24 volt systems in there when its not necessary and it just makes more work with your charging system when you add your house batterys.Also if you have everything 12 volt you could use your house batterys to start your bus in a emergency with the simple flip of a switch or relay system.
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« Reply #3 on: March 11, 2008, 10:21:44 PM »

much easier to make a 24 volt house system
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« Reply #4 on: March 11, 2008, 10:25:33 PM »

Probably because of the big blowers on the A/C systems of the buses is why they have 24v systems.  I can tell you that all American trucks are straight 12v.  They were thinking on changing to 48v or 56v under power (4-31's in series instead of parallel) for engine computer, but the engine companies have beat the truck manufacturers to the punch by having either a built in converter or inverter (Cat uses 120vac) to punch up the juice.  Personally-I really like having a straight 12v wired bus-including the starter.  Makes for much more simplicity.  My truck does have a 24v starter, which would be easy enough to switch over-but haven't had much problem with it.  Good Luck, TomC
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« Reply #5 on: March 11, 2008, 10:35:24 PM »

 When I researched this I decided it was quicker, eaiser, cheaper to go to a 24V house system. I'm happy with that decision.
 
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« Reply #6 on: March 11, 2008, 10:36:24 PM »

Hi Tom , I am probably not going to use the bus A/C so i dont think i need 24v cause that is the biggest need for it. I just think the 12 volt systems are more common and easier to deal with when you need a jump start. thanks for your input.
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« Reply #7 on: March 11, 2008, 11:07:51 PM »

unless you plan on rewiring the whole coach....some 5 miles of wires.....just go witha  24 volt system....save yourself alot of headaches tracking down problems.

24 volt system wires are going to be too small to carry 12v

the main reason they use the 24volt is the cost of copper
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Sean
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« Reply #8 on: March 11, 2008, 11:56:43 PM »

... I figure all the lights are 12 volt anyway so why not simplify the system and make everything 12 volt.       


Chris,

I think you'd better re-figure.  If that's an MCI I see in your photo, all the lights are 24-volt except the headlights.  Here is a partial list of what you will have to change, starting with the most expensive items:
  • Starter
  • Alternator
  • Tail, brake, turn, and marker lights
  • All gauges except air pressure
  • All dash illumination
  • All warning lights and buzzers
  • All relays
  • All the wire to all the lights and some of the controls (wrong gauge)
  • All battery cables (wrong gauge)
  • Alternator and starter wiring (wrong gauge)
  • Likely some engine sensors and harness wiring.

I'm sure there's something I've missed, and I am equally certain that after you're "done" with such a project, you will only then find out something you've missed, too.  If you're lucky, it will just not work -- if you're not so lucky, you could have a fire, fry something expensive, or worse.

In short, I think this is a fool's errand.  Also, 24-volt systems actually make much better house systems, as has already beed suggested to you.  You get to use smaller wire for everything, which really helps with the big stuff like inverters, you can get bigger inverters in 24-volt, and it's easy to transfer power from the alternator to the house system, or, if needed, the house system to the starter.  There is really only a small handful of electrical items that are only available in 12-volt and not 24.  FanTastic fans come to mind, along with LP alarms, and the control boards of RV appliances.  For these minimal loads you can center-tap the batteries and add a small equalizer -- waaaay cheaper than trying to change your bus over to 12 volts.

FWIW.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #9 on: March 12, 2008, 02:45:53 AM »

Amen to all above posts!

Example…..back in the old days before 1955, it was all 6 volts in cars and light trucks and farm tractors. Whenever we start our vehicle it was always common to cranking fast enough to get it fired or run the battery down. But since 1955…the 12v came out….wow….it begin to take away the fear of not firing to running everyday.

Liked what TomC said that 42v is in the planning stage to be release to the public soon.
This is even better for starting as well smaller wiring and faster turn on lighting & accessory. They say that new system will be design to kill engine at stop light and restart as soon you depress accelerator pedal like does in gasoline power golf cart now. It to save on fuel usage.

By the way…most farmers went to 8 volts battery to starts 6 volts tractor in colder climate.

24 volt system is your low cost way to go due wiring (smaller gauge) already in your coach.

FWIW

Sojourn for Christ, Jerry

PS…..Thanks Sean for so well written and informed reports.
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« Reply #10 on: March 12, 2008, 05:28:35 AM »

Chris,
All of the reasons for why not to get rid of your 24V system are about why the disadvantages to switching, but you need to also be told of the positive reasons for keeping it.  If your bus air conditioning is toast and you plan to remove it, how were you going to cool it while going down the road?  Genset?  Diesel or gas?  How about this - get a Xantrex SW 4024 4KW inverter (it is a 24V model), run it from your bus alternator, and run 2 roof air conditioners while driving.  No extra tank for a gas genset,  no fuel loss to run a diesel genset.  Just add 2 group 31 start batteries to your bus, and use the 2 big 8D's for your inverter.  Of course at some time you would want to upgrade the battery type, and maybe expand the bank, but that's not what this thread is about.  Good Luck!
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« Reply #11 on: March 12, 2008, 05:48:33 AM »

Well, I guess my question to you would be, what kind of condition is the electrical system in that is presently installed in your bus.  I switched my bus electrics to 12V (including the starter and alternator) almost 10 years ago.  Of course, the system that I had in the bus looked bad and the panel near the driver looked like a drunk bus employee was working on the wiring and it was just ugly in general.  As a result, I pulled all of the bus wiring out of mine and started fresh with boat grade electrics and tinned wire. There is a bit of work to any bus that you don't know the history of repairs on and by installing your own system you know what is connected and what isn't.  It wasn't that difficult to get done, just time consuming and many many rolls of wire.  And as a result, everything works and the possibility of a short due to the 30+ year old wire or poor prior repairs is eliminated.
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H3Jim
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« Reply #12 on: March 12, 2008, 07:44:41 AM »

FWIW,
I made my house system 24 volts, kept the bus system at 24 volts.  I'm very pleased with the way it has all worked out.  I would say if you have to replace it all anyway because its bad or dangereous, have at it, but if it works, why fix it.  It sounded like your main fear is needing a jump start and not being able to get it.  If you have a 24 volt house system you're all set and can jump yourself.

And with a 24 volt sytem, if you need to jump start your truck, boy will that sucker spin! (just don't have anything else turned on or you will  fry  it)
« Last Edit: March 12, 2008, 12:14:21 PM by H3Jim » Logged

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« Reply #13 on: March 12, 2008, 11:36:39 AM »

FWIW,
I made my house system 24 volts, kept the bus system at 24 volts.  I'm very pleased with the way it has all worked out.  I would say if you have to replace it all anyway because its bad or dangereous, have at it, but if it works, why fix it.  It sounded like your main fear is needing a jump start and not being able to get it.  If you have a 24 volt house system you're all set and can jump yourself.

And with a 24 volt system, if you need to jump start your truck, boy will that sucker spin! (just don'e have anything else turned on or you will  fry  it)

Several years ago I was deeply involved in building sand rails for use in the desert. The common engine was either a VW or Corvair.
On all of these vehicles we installed a 6 volt starter with a 12 volt electrical system. That really cranked the engines over fast and made for good starting. In all the years doing this, I never had a starter failure and have not heard any of the other people doing this having a starter failure.

Richard
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« Reply #14 on: March 12, 2008, 02:38:07 PM »

Richard, back in the late 60's and early 70's we did the same thing with the VW's. The problem we had was that the ignition coils would fry. even if we used a 12V coil with a condenser, we could plan on a replacement at least once every few days.
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« Reply #15 on: March 12, 2008, 03:15:04 PM »

Richard, back in the late 60's and early 70's we did the same thing with the VW's. The problem we had was that the ignition coils would fry. even if we used a 12V coil with a condenser, we could plan on a replacement at least once every few days.

I do not remember having any coil problems. Can't remember if we used a resistor in the circuit or not, but I suspect we did.

Richard
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« Reply #16 on: March 12, 2008, 03:47:25 PM »

Actually all the 24V lighting will work on 12 volts!!!!!  It will just be real dim.  So I dont get flamed I will mention that this is not practical for running, stop, turn lights etc.
 The Xantrex true sine wave inverters are nice, but you can use less expensive inverters like the Xantrex DR 3624 for 24 volt systems.
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« Reply #17 on: March 12, 2008, 07:31:56 PM »

Chris,  I did.  I put in an 12v electronic motor and figured it would be best for me. The big down side I see is the inverter 24v is closer to 120. At the time I did not plan on putting one in but after the talk here I changed my mine. Thats the problem working years on these things ideas change. I now know what wire is on every terminal. Beware I am NOT an engineer, I just play one in my garage.  Tom Y
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« Reply #18 on: March 12, 2008, 09:04:49 PM »

Ok everyone, I guess the overall answer is leave the old system and save alot of work. I  really did not realize that there was so much 24 volt stuff available for inside the house part of the bus. I will research the appliances and all the other parts i need for inside. Also thanks everyone for your input,can you all give me your brand and model of your inverters because i will probably run a basement a/c /heatpump for over the road.
                             Thanks again  for all your help    Chris
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« Reply #19 on: March 12, 2008, 10:03:19 PM »

I have lots of 24 volt lights (MR16, florescents from the bus, bus lighting for the bays, other lighting left over from the bus), my refrigerator is 24 volt, my water pump is 24 volt.  I have an equalizer that I just use as a voltage splitter, so I have lots of 12 volt available for fanastic fans, some 12 volt lights, latching relays to switch all my lights, proposed ceiling fan.

I am trying to use all dc lighting, so I can have lights without turning the inverter on, particularly overnight.  The small loss from an idling inverter really adds up over a lot of hours.
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« Reply #20 on: March 12, 2008, 10:19:42 PM »

... I  really did not realize that there was so much 24 volt stuff available for inside the house part of the bus. I will research the appliances and all the other parts i need for inside.


Chris,

Just to save you some time and frustration:  you will not find any "24-volt light fixtures."

For incandescent lighting, basically, a fixture is a fixture -- you buy 12-volt fixtures, and, if they have bulbs in them already, you toss the bulbs and replace them with 24-volt models.  Almost every style of 12-volt incandescent bulb also comes in 24-volt, however there is usually a price premium.  Finding the bulbs takes a bit of research, but they are widely available on the internet (shop around, prices vary considerably).  Like Jim, we have quite a few of the projector-lamp style (MR-10 or MR-16) fixtures, which we have on low voltage tracks.  We run all of it at 24 volts.

If you prefer LED lighting, you again buy those in 12 volt models, but buy them in pairs, and wire each pair in series.  Just make sure that you wire together only pairs of identical lights.

Fluorescent is another story.  Here you will need to find fixtures with 24-volt ballasts, or use 120-volt models (much cheaper anyway) and run them from your inverter, or run 12 volt models on 12 volts from the battery center tap, with an equalizer.

For water pumps, FloJet and Jabsco both sell a more or less identical 4.5 GPM variable-speed pump that works on 24 volts (or 12, it's a multi-voltage item).

Most of the low voltage marine refrigerators now use the Danfoss compressor system which is also dual voltage and works on either 12 or 24.

FanTastic fans, LP alarms, and the control boards of RV-style appliances like LP water heaters and absorption refrigerators are all 12 volts -- you'll need to run those from the center tap.  Again, an equalizer is recommended to keep the batteries discharging/charging evenly.

To answer your question about what inverter we chose, here is a link to our construction web site, with way more detail than you ever wanted to know about our electrical system, including all the specifications, drawings, and diagrams:
http://ourodyssey.us/bus-conversion.html
(scroll down to "Odyssey's complex electrical system")

HTH,

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #21 on: March 13, 2008, 08:05:43 AM »

One of many on the net with 24V bulbs. They carry two grades Brand Name and the same bulb in generic for much less money.
                             https://www.bulbdirect.com/index.php
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« Reply #22 on: March 13, 2008, 04:52:03 PM »

hello;     
    Some thoughts on 24Vstuff and alternative ways of doing things.. 
 
      24V ballasts are available . Look up alternative energy websites and you can get catalogs of stuff. You will also find an equalizer that Can go across the 24V batteries that will allow you to charge your batteries so that you do not discharge one battery more than the other.  The 12V equalizer post on the equalizer will provide 12V power for water pumps 12V fluorescent lighting ,fantastic vents and any other item that you cannot find in 24V.. I have a 20 amp equalizer on my battery bank that is used for the above mentioned items because when I installed those items nothing else was available.. Now there are cheaper products available for 24V applications.
     Why 24V   well the short answer is more bang for your buck. using the old water hose analogy. water pressure is the equivalent of voltage.  So the more pressure the farther the stream  out the hose goes..   Amps or amperage is the electrical equivalent of water flow.   How many gallons per minute vs amps flowing in a circuit. 
    The next part is watts or power..  Power watts is amps X volts   so  24V X 10 amps is 240 watts    10 amps X 12V is 120 W oh so it will take 20 amps at 12 volts to equal what 10 amps at 24V will do..   Get the picture more volts equals less amps for equal amounts of power .    Batteries store amps so more power is available using the same space and weight. 
      Then  the other good thing about higher voltage is that you can use smaller wire if you raise the voltage..    With higher voltage you need to shield the wire better (provide better insulation) so that the voltage does not jump out and go to ground  ie short circuit..  All elecricity likes to go to ground  thats its main function in life..  WE just make it do useful stuff for us on its way to ground.  (If you get between the electricity and ground that is is a bad thing because your heart beats because of very very small pulses of electricity and It does not take much to swamp the circuit and stop your heart.   (  8 to 15 milliamps is enough to cause that condition)) .
        Witness lightning...   millions of volts     goes   to ground wherever it wants to ; not enough resistance to stop it..

   Other parts of the subject are impedance and resistance , AC vs Dc and circuit breakers ,grounding , ground faults  etc etc etc.
     Those subjects and the  longer answers takes alot more time and many books have been written on the subject.
  ANyone can learn about electricity and its many uses  by reading..   ..
         FYI    and FWIW   the info above is mostly right but can be corrected because many things have filtered through the old mans mind over the past  6 or so decades . 
       Happy bussin  mike   
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« Reply #23 on: March 13, 2008, 08:27:29 PM »

Don't forget that aircraft and some military items also run 24-28 volts so there's another option for lighting if you want to get fancy or go rummaging through a surplus store...or aircraft salvage place.

The other thing is that most people that strip out transit buses might still have the 24 volt electronic flourescent ballasts. They can run some pretty big or small single-pin lamps. Some are out there that are 12 volt also, You have to look at the labels..

Just a few ideas....

Dave....

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