Coach Electrical Systems

[PNWorBUST72]

Ok so 24v system with an aftermarket Vanner unit to run the 12v headlights and etc....

Do you guys justy all DIY this or do you contact local electricians to help you plan this stuff out?

[windtrader]

The MCI the 24v coach system does drive 12v headlamps. Some have been converted, mine has a plate on the left side driver panel stating 12v lamps. Later ones I believe are factory wired for 12v. It does not seem like using a Vanner 24 to 12 is recommended for driving headlights

[bevans6]

Later MCI's in the 1980's had a nice 12 volt headlamp solution that could be retrofitted to an older bus, or a variant used.  The right hand pair of headlamps were powered from 24 volt power bus to a 12 volt center tap, and the left hand pair of headlamps were powered from the 12 volt center tap to ground.  Any light could fail and the others would still work.  As long as both sides were lit the batteries stayed balanced.  relays were used to access the center tap and to do the high/low beam switching.  No other equalization was required as long as you didn't run for weeks with only one working headlight.  Conversion issues would be running new heavier gauge wiring to carry the 12 volts to the headlamps, finding and installing suitable relays (I think one more than stock was required for the conversion), but once done, done and dusted for a good long time.

Personally I ripped out and threw away an aftermarket 12 volt conversion (sold by MCI) and installed halogen lamps with 24 volt bulbs. Superior solution, used stock wiring, great light, bulbs are available on-line and I carry spares.  Very happy with my solution. 

Brian

[buswarrior]

Ok so 24v system with an aftermarket Vanner unit to run the 12v headlights and etc....

Do you guys justy all DIY this or do you contact local electricians to help you plan this stuff out?

Do it yourself, or suffer the consequences?

There is no ready supply of paid help out there that is trained in designing, engineering and installing alternative systems in ancient motorcoaches.

Oh, there's lots who will pretend, and try to educate themselves, and you, on your dime...

Mechanics are trained to replace parts on vehicles designed and engineered by others, with charts, manuals, online resources, and training.

When you were a teen, who was heading to auto shop, and you want to hire them to do what?

Few come back on here and brag they wrecked their coach by paying the wrong guy...

Teach yourself by reading authoritative publications, certainly not via social media...

happy coaching!
buswarrior

[Debo]

I don't know if this will work for your purposes or not, but it's worked reliably and fine for mine for 4 years. Samlex makes a 24v to 12v converter that is good for up to 30 amps of 12v output. (I think mine was less than $100.) I have a 24v chassis electrical system ('81 MC9), a 120v house system on a Magnum Hybrid Inverter (24v), and a 12v - I'll call it "auxiliary" system powered by the Samlex.

I use the aux system mostly for my 12v LED lighting, and my 12v suburban furnace. I just wanted the ability to run a few 12v things if there was something I liked that was only available that way. That's the beauty of these things. You can build it any way you want to.

[bevans6]

The typical 24 volt to 12 volt converter like the Samlex is a regulated power supply that actually puts out 12 volts exactly.  The problem with using that type of converter with headlights is that headlights (and all automotive light bulbs) are designed for an automotive "12 volt" system that actually is 14 volts when the alternator is operating.  That means that headlights will be significantly under voltage when powered by a true 12 volt converter. 

[Debo]

Makes sense. Just to clarify about the Samlex, it'll accept anything from 20-32 VDC, and the output is actually 13.8 (12v nominal). May or may not work for the headlight application. Just another data point. Bus on, good people!

[chessie4905]

I have one of these:

https://www.amazon.com/Pyle-PSWNV720-Power-Converter-Technology/dp/B003P17X8I/ref=sr_1_3?ie=UTF8&qid=1522156282&sr=8-3&keywords=24+volt+to+12+volt+converter

Used for small loads, pulse air wipers, King cruise control, electric sunshades,gps.
I also have a Vanner. This will make wiring easier for at dash items.

[bevans6]

13.8 is perfect for automotive use.  I was looking some years ago for a converter for my trailer light relay box, and only found regulated 12 volt supplies, I suspect intended for powering a computer or TV.  What I went with was a 20 amp converter that is actually a small equalizer, it takes in the 24 (or 28 volts actual) volts and precisely divides it in half and outputs that.  It can also work backwards and take in 12 volts and output 24 volts.  It was very funny, I powered it from the rear 24 volt bus in the engine bay electrical panel.  The first time I plugged in my trailer, all the rear lights started to work because the little brake battery on the trailer was connected to the 12 volt side of the converter, it turned that into 24 volts on the 24 volt bus, and my brake lights turned on!

[Oonrahnjay]

I have one of these:

https://www.amazon.com/Pyle-PSWNV720-Power-Converter-Technology/dp/B003P17X8I/ref=sr_1_3?ie=UTF8&qid=1522156282&sr=8-3&keywords=24+volt+to+12+volt+converter

Used for small loads, pulse air wipers, King cruise control, electric sunshades,gps.  I also have a Vanner. This will make wiring easier for at dash items.  

    I like this one. It appears that it puts out about 12.8V at standard conditions so it won't charge a 12V battery very well, but the user ratings show that it's reliable at the 360W Continuous that it claims and you can do a lot with 30Amps of 12V power.   It's limited but the reports are that it performs well within its limits.  

[eagle19952]

    I like this one. It appears that it puts out about 12.8V at standard conditions so it won't charge a 12V battery very well, but the user ratings show that it's reliable at the 360W Continuous that it claims and you can do a lot with 30Amps of 12V power.   It's limited but the reports are that it performs well within its limits.  

from commentsat Amazon.
"I have paralled 2 and it works, however the load sharing is not equal..I'm sure this would void any warranty of course..I also increased the voltage out to 13.2v on both units by adding a trim resistor at the appropriate circuit connection..again, this will obviously void any warranty".

[richard5933]

Could you provide a bit more information? I'm not sure what you decided in the end about coach vs. house batteries, so it's really hard to make any recommendations.

What I've gathered so far is that you've got a 24v coach system. Sounds like you're adding a 24v house battery bank. Sounds like your most recent post is trying to figure out the best way to run the 12v loads that you'll have for both the house and coach systems.

Did I get that roughly correct?

[PNWorBUST72]

I am not sold on either option to be honest.

Having a 24v house bank that can be charged from the alt makes alot of sense.  But, and I haven't looked myself much, the difficulty in finding all the lights/USB charges/ appliances that can run on 24v seems to be an issue.

For now, I am hoping to get a simple 120V system installed so I can plug in at the storage yard I am at.  But I DO NOT want to have to do all this over again when I add say a genny later so planning is important.

50AMP plug, load center/circuit breaker and some romex for 1-2 outlets inside the bus basically...maybe a dedicated 15A plug since I will be using a standard outlet to start with.

[richard5933]

Thanks for the extra information. I think that the first step would be to really think through all the items you'll have inside the bus running on electric power when things are completed. You can then work backwards from there to determine which system works best for you.

Some go with all residential appliances and devices and little or no 12v DC need. When plugged into the pole or on generator these systems are basically just a little house on wheels. When on the road, they operate the 120v system by powering an inverter from battery banks.

Others manage with all 24v DC systems. Lots of 24v DC devices and appliances are available, mainly for use in marine applications and on trucks.

Some do like we did and have a 24v chassis system and a 12v house system plus the 120v for use when on pole or generator. We also have a few 120v outlets powered by inverter to enable us to use TV, etc. while boon docking.

Which you go with really depends on your end goal. Once you have a clear end game it will be much easier to make specific recommendations.

[scanzel]

My 8 AGM battery bank is 24v with a 4000 watt Magnum inverter for AC, 24v items run off 24v and items that I could not find 24v run off a 12v battery tap backed up by a 100 amp Vanner equalizer. The 12v/24v wires are wired into a Blue Sea Systems fuse blocks using basic automotive fuses clean and simple, each fuse block also has a volt gage next to it so I can monitor voltage. All my electrical is mounted in a cabinet in the bedroom so I can monitor everything from inside the coach. If you are not up on AC/DC electrical learn as much as you can before you tackle it. One mistake can either be fatal or cause damage to yourself or damage some expensive items. AS they say miss wire a unit and you will let the smoke out.