Coach Electrical Systems

[belfert]

An equalizer basically monitors two strings of 12 volt batteries to be sure they are equally charged.  You center tap a 24 volt battery bank for 12 volt power and the equalizer makes sure the batteries stay at equal states of charge.  I absolutely would not try to run a 12 volt inverter off a 24 volt battery bank. 

Yes, busnuts often add a second 12 or 24 volt alternator for the house bank.  I recommend an external regulator instead of an internally regulated alternator.  You can get external regulators designed for charging deep cycle battries

[richard5933]

...12v makes no sense to me.

Some things used in a conversion/RV are just easier to find and source in 12v format, like a Fantastic Fan and other appliances. Correct, many of the things that we'll be using can be had in 24v formats, and even a phone charger can be made to run from them. However, try finding something like a dash radio or CB radio that is going to run out of the box on 24v and you'll have more limited selection. In my opinion, there is wisdom in having 12v circuits available, even if the house batteries are set up in a 24v format. Since it's really simple to do this it shouldn't present a problem.

To get 12v from a 24v battery bank is really quite simple. There are two ways to do it. One way is to use a 24v-to-12v converter. You just connect the input of the converter to an appropriately sized 24v DC source and you will have 12v DC available at the output. For the most part this method reduces the voltage by converting it to heat, so it's not the most efficient.

Another way to get 12v circuits available is to connect an equalizer to the 24v battery bank. Follow the instructions provided by the manufacturer of the equalizer to connect the equalizer, and it will draw the power from both batteries and not cause one to draw down more than the other. This method could be more efficient, but it is also more expensive. Here is a manual from Vanner which should provide some more information: http://www.vanner.com/manuals/EQUALIZER-60-SERIES.pdf

Don't confuse the equalizer with the inverter. An inverter is used to create AC power from a DC battery bank. You would use an inverter to make AC power when you are not connected to shore power or generator. Some inverters are packaged with the battery charger in the same box. How to connect them to your system will depend on what type of bells and whistles are included such as automatic transfer switch, charger, etc.

Inverters are matched to the voltage of the battery bank, so if you have a 24v battery bank you use a 24v to 120v inverter. Remember that DC amperage required to power an inverter goes up as the voltage goes down. In other words, to get the same 2000 watts AC from an inverter on 12v DC will require twice the amps as it will from 24v DC. Interters running on 24v are more efficient and require smaller connecting cables as an inverter with the same AC output would on 12v DC.

An equalizer is not the same as an inverter and is not interchangeable. Equalizers are used to pull 12v from a 24v battery bank while maintaining equal charge in all the batteries. If you tap into a 24v battery bank to pull 12v you will discharge some of the batteries but not all when running the 12v load. When your charger kicks in, it will overcharge the batteries that were not discharged and/or undercharge the ones you were drawing down.

[PNWorBUST72]

I THINK I am more inclined to keep the systems separate, maybe adding a solar controller and a single solar panel to keep the 24v system charged...

[Branderson]

This thread has reaffirmed to me that i have very little knowledge on electricity.

[Geoff]

My bus came with both 12v and 24v.  I removed the AC and big heater so I had no use for a large 24v system and hand grenade alternator (50DN).  I went with a 12v house system.  Much easier for RV stuff, and all my lighting was already 12v.  I added a 180 amp 12v and a 65 amp 24v alternator.  Works out great.

[chessie4905]

They like to call gear driven alternator hand grenades....yet, thousands of city and highway busses and coaches used them for millions of miles. If they were that troublesome, I'm sure they wouldn't be around that many years. Could be some weren't adjusted at the mounting adapter properly, or bearing went bad causing catastrophe. I don't know if they have a periodically servicing schedule.

[Geoff]

They like to call gear driven alternator hand grenades....yet, thousands of city and highway busses and coaches used them for millions of miles. If they were that troublesome, I'm sure they wouldn't be around that many years. Could be some weren't adjusted at the mounting adapter properly, or bearing went bad causing catastrophe. I don't know if they have a periodically servicing schedule.

You just have to look at the damage the gear driven 50DN can do to be wary.  It might not happen that often, but I have seen it happen, and I don't need to take the chance.  There was never a day that I drove my bus with the 50DN that I didn't worry it would blow and ruin my engine.  I took it off, made a steel plate to cover the hole, and breathed a sigh of relief.  Big fleets can absorb the repairs, but for individuals it is a big hit.

[buswarrior]

You know, this yak yak about gear driven alternators catastrophically failing is NOT something that was discussed years ago...

So, what is it?
Peeps repeating rare things, making them common?

Peeps re-using worn parts that shouldn't be in service?

Peeps unable to identify worn/failing components?

Peeps not inspecting anything, missing the loosening fasteners, etc?

If we repeated every rare and wild failure that everyone ever heard of... nobody would dare operate their coach?

Happy coaching!
Buswarrior

[luvrbus]

Fleets pulled the 50D and serviced it every 100,000 mile to changed the bearing and the drive gears per the book,they will destroy a engine I have seen it more than I liked and they will brake a cam  
I have a 8v92 here in the shop now the 50D broke the cam in, no way I want one hanging on the back but to each his own.There are photos here on this board that shows what can happen when the 50D turns loose not a pretty sight    

[buswarrior]

For balanced reporting, in a Big Transit setting, back in the day, 1700 2 stroke buses, nobody even thought about an alternator locking up. Sure, they stopped charging, but with gear drive/oil cooling, bearing lubrication was assured, vs the old belt drives. They were run to failure, or engine re-build. Nothing special done. Alternators were re-built in shop, dedicated bench job, returned to spec.

Like being hit by a meteor, yes, it is possible, but likely??

So, perhaps the advice to busnuts is a reminder to pay attention to the preventive maintenance on gear driven alternators, because if allowed to get into poorly maintained or grossly negligent condition...

We need to be careful that "negligent" doesn't become "normal" and have a busnut spending money where none needs to be spent?

There's already lots of more pressing stuff to worry about in an old coach?

Happy coaching!
Buswarrior

[luvrbus]

OK but I never knew of a transit co or a top notch tour operator like Boomer that didn't service one.the only transit co I was around was Houston Metro though and they just pulled it and replaced with one from inventory and rebuilt the old one,it's not like one has special bearings all they have is a cheap @$# single row bearing inside to replace   

[bobofthenorth]

If you have 100 coaches and one fails that's a 1% failure rate - maybe you'll live with it or maybe you won't but its a 1% failure rate.  If you have one coach and your alternator takes out your gear train that's 100% failure rate and its a catastrophe. 

You can't apply the same rational percentage failure based thinking that a large enterprise running a fleet of modern coaches uses when we're talking about end of life single coaches maintained by amateurs.  If the potential damage at failure is catastrophic, there is no penalty for taking remedial action and the cost of that remedy is nominal then it probably makes sense even if in a commercial setting it might not be cost effective.

[Geoff]

The last time I heard of a price to have an electrical shop rebuild a 50DN it was around a $1000.  Plus getting it on and off.  I don't need a 300 amp, 24v alternator.  So I run belt driven alternators and never worry.

[luvrbus]

The last time I heard of a price to have an electrical shop rebuild a 50DN it was around a $1000.  Plus getting it on and off.  I don't need a 300 amp, 24v alternator.  So I run belt driven alternators and never worry.

They are slowing going away the 24v is the only 50D you can buy parts for now even Kirks doesn't have parts for the 12v now and he said the 24v parts are getting hard to come by,a bus engine is the only place you find a gear driven 50DN 

[PNWorBUST72]

How can I tell what alternator I have?  I assume there is the standard OEM one?

Where do people mount secondary 12v alternators?  Pics?