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Author Topic: Separate 12 volt alternator  (Read 3337 times)
Lin
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« on: February 14, 2010, 06:46:06 PM »

I know that some have separate 12 volt alternators for charging the house bank.  Where would one be attached to an MC5 8v71?
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robertglines1
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« Reply #1 on: February 14, 2010, 06:52:23 PM »

Ran off pulley on right side of motor looking at it from back of bus...use to charge gen battery...ran a exciter wire from rear junction box...8v92 detroit
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« Reply #2 on: February 14, 2010, 07:11:37 PM »

Lin,

Don't have an MCI, but I hope my GM pictures help you anyway.  I believe my 8V71 is similar to yours.

The alternator is a Delco Remy "1 wire", available at just about any automotive supply store.

Charged my 2 6V deep cycle batts wired in series for our 12V house system.

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Chris & Cheryl Christensen
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« Reply #3 on: February 14, 2010, 07:13:32 PM »

Another picture of alternator.
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Ed Hackenbruch
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« Reply #4 on: February 14, 2010, 07:24:38 PM »

Lin, the PO put one under my air filters on my 5A and ran the belt for it off of the 24 volt alt.
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« Reply #5 on: February 14, 2010, 07:30:20 PM »

Anyone have one mounted on a 6V92 ? With that mounted "backwards", is the rotation an issue ?
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« Reply #6 on: February 14, 2010, 07:36:37 PM »

If I remember correctly an alternator doesn't care what direction it is turned to make juice however the fan is directional. I mounted a 12 volt alternator and ran 12 volt power from it to the house batteries and also clear to the front of the bus to  power the headlights, radio and various other 12 volt systems.
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« Reply #7 on: February 14, 2010, 07:43:04 PM »

You can use a pulley driven by the rear of the blower as Robert suggested but I don't think there would be room for your 24 volt alternator. I'm hoping to use my front   a/c  mount to run mine.
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Gary '79 5C
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« Reply #8 on: February 15, 2010, 03:36:30 AM »

Lin,

If you have deep sixed your coach A/C, another idea would be to get a Vanner equalizer to pull 12V from your start batt's.

The OEM alternator certainly has the capacity, and I would install a 24V relay such that it separates your start batt's from your house batt's when the engine is not running. That relay can be cannibalized from the condenser motors of the previously used coach A/C. Mine was located on the ceiling of the forward bay.

FWIW, I have gotten rid of the OEM alternator and have installed a standard truck J180 alternator 24V in its place.

Good Luck,
« Last Edit: February 15, 2010, 05:03:00 AM by Gary '79 5C » Logged

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Tom Y
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« Reply #9 on: February 15, 2010, 04:19:37 AM »

Lin, I have 2 alternators on my Cummins also. Keep in mind if you use a 1 wire unit and your batteries are not close they may not get fully charged. It sees the voltage at the alternator, I think a 3 wire will allow you to see the voltage somewhere else.  Tom Y
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« Reply #10 on: February 15, 2010, 05:02:23 AM »

Lin, I have 2 alternators on my Cummins also. Keep in mind if you use a 1 wire unit and your batteries are not close they may not get fully charged. It sees the voltage at the alternator, I think a 3 wire will allow you to see the voltage somewhere else.  Tom Y

Tom,

I read, but did not fully understand. My read of your comment is that if the start batt's are forward, with 20+ feet of 30 year old cables, the voltage drop will not allow full charge of those batt's.

I may be missing something here and just looking to clarify. Slow morning so far for me...
Thanks.
Gary
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« Reply #11 on: February 15, 2010, 05:50:09 AM »

Gary, This is my take on it only. I was reading about the 1 and 3 wire units. If you have a load on your batteries ( they show 12v ? ) your alt may be seeing 14v so it stops charging. With the 3 wire unit 1 wire is checking voltage at a terminal point seeing the 12v and keeps it charging. I MAY BE WRONG. That being said, I put in 1 wire alts but my batts are a few feet away.  Tom Y
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« Reply #12 on: February 15, 2010, 05:54:47 AM »

the idea is that an alternator with an internal regulator uses a reference voltage to determine it's output voltage.  With a one wire alternator, the output voltage and reference voltage are identical, so the opportunity for the alternator to be putting out say 14.5 volts and have that voltage reduce to a lower number at the battery over a long cable exists.  The bus alternator for the start batteries, in my MC-5 with a stock setup, uses an external, adjustable regulator so you can set the voltage at the batteries to what you want.

I think, although I haven't thought it through and haven't checked voltage loss tables, that a house battery charging alternator won't be putting out that much current unless you are asking it to run inverters for high wattage loads like AC units and such on the road, which isn't the best application for a small 12v alternator anyway, so the voltage drop will not be an issue.  if you do plan to be pulling a lot of current, then look up the proper size cable for the application.  And it's always good practice to measure charging voltage at the battery itself, since it's the thing that cares what the voltage is or is not.

Brian
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« Reply #13 on: February 15, 2010, 06:19:22 AM »

Lin, you can run the alternator from the front cam shaft pulley



good luck
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« Reply #14 on: February 15, 2010, 06:30:01 AM »

Anyone have one mounted on a 6V92 ? With that mounted "backwards", is the rotation an issue ?

Only issue with a "backwards" rotation is the direction of the cooling fins on the alternator pulley.  They are available in left & right rotation as well as straight fins that will work in either direction.  Jack
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« Reply #15 on: February 15, 2010, 06:40:37 AM »

Clifford,

Would it make sense to run it off the camshaft pulley and mount the alternator to a truck a/c front mount? Something tells me this might actually work.

I would much rather do that than run it off the crank pulley.

FWIW I'm not trying to horn in on the thread for no reason, I am planning on adding a 12 volt alternator for my house batteries as well.

Rick
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« Reply #16 on: February 15, 2010, 07:19:24 AM »

When I thought about adding an alternator to my MC-5C, my plan was to drop one of the four belts to the DN-50 off, and run the 12v alternator from the pulley on the DN-50.  It would all depend on if the three belts remaining could run the DN-50 when the bus heater motor was on.  Since I have a Vanner, the other idea is to charge the 12v house batteries from that.  But the Vanner documentation really emphasizes the need to have balanced batteries in the 24v "stack" and obviously if you add say 240 amp/hours of deep discharge 12 volt battery in parallel with one of the 8D start batteries, you don't have much balance anymore...  What will happen if you try that?

My Vanner is a 60 amp deal.

Brian
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« Reply #17 on: February 15, 2010, 08:01:17 AM »

Brian, my 12v alt. runs off of the 24v pulley and the heater motor works just fine. The only thing i would like to do a little differently is set it up so that the belt runs off of the first groove instead of the last. Makes it a lot easier to replace the belt for the 12v if you don't have to take off the other 3 first. Smiley  I had also kicked around the idea of moving the whole thing to the right corner and running off one of the pulleys there but i just don't have enough room there to be comfortable with it.
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Lin
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« Reply #18 on: February 15, 2010, 10:10:33 AM »

Thanks for all the info.  Just to clarify, I should have mentioned that I do not have a 50 DN on the bus.  It is a 45 amp, single wire set up on the left back running off 2 belts from on pulleys there.  I actually have a rebuilt 50DN in the garage but do not see ny reason to install it.  Since the OTR heat and air have been removed, I do not need all that power.  I just need an over-the-road house battery charger, which a little 12v alternator would do fine.  
« Last Edit: February 15, 2010, 10:23:12 AM by Lin » Logged

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Lin
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« Reply #19 on: February 15, 2010, 12:15:06 PM »

Hey now, don't yell at me for asking this, but I am curious about whether I could charge the house batteries by center tapping the coach batteries with a manual switch.  Does this seriously unbalance things?
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« Reply #20 on: February 15, 2010, 12:47:24 PM »

Use the three wire system and sample at the bat post.  Even the inverters sample at the post and they are the best bat chargers out there.

I don't agree about the 50 DN.  I think it puts out 2 or 3 hundred amps and your inverter will gobble that up nicely running a roof top down the road.  You may have coach air, and I hope you do, but if it fails you understand that in a hot climate you cannot tolerate the interior of a bus in the sun.  That goes for running down the road/ also.  Being able to run the roof tops anytime is a serious backup system.  I think you need something like 120 amps to generate the 12 amps at 120 volts so you need a 50 DN or close.

John
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Lin
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« Reply #21 on: February 15, 2010, 01:14:01 PM »

John,

You are certainly right about having the option of running roof air on the road.  Since we do not have dash air, we do that a lot using the generator.  However, changing over to the 50DN would be a chore.  We have a one wire system now, so we would have to re-establish that former system with a voltage regulator.  We would also need to get a big enough 24volt inverter and a Vanner equalizer if the house bank would also be 24 volt.  Aside from which, the current alternator is relatively easy to change should it go bad, but the 50N is a monster that I suffer to lift even the best of locations.  I doubt I could handle the R&R of one alone if I had to.  Therefore, I think that the current compromise situation is acceptable. 
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« Reply #22 on: February 15, 2010, 01:38:40 PM »

Hey now, don't yell at me for asking this, but I am curious about whether I could charge the house batteries by center tapping the coach batteries with a manual switch.  Does this seriously unbalance things?

Yes, it does.  The amount of imbalance will depend on the particular batteries in question, and the importance of that will depend on how much you care about battery life.  Basically one battery will get well over charged and the other (the "lower" battery with the house batteries paralleled off, I think) will be undercharged.  The Vanner is, simplistically, a power supply that is powered by the 24v supply that forces the center tap to be exactly equal to half of the total supply, thus the batteries are forced to be equally charged.  Now, the Vanner website specifies that there can be a "load" of up to 60 amps and that the batteries have to be identical.  Obviously if you contemplate charging the house batteries as the "load", the batteries are no longer equal.  I have found no one to tell me if using the Vanner to charge the house batteries is an "allowed and recommended" way to use a Vanner.

Brian
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« Reply #23 on: February 15, 2010, 05:54:50 PM »

I have used a Vanner to charge my 12 v house Battery's (4 8D's) for 6 years and it works fine.
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« Reply #24 on: February 15, 2010, 06:18:03 PM »

Terry,

How did you do that?  Did you just connect the output of the equalizer to the house bank as if it were a battery charger?  Did you have it on a manual switch or was it a fulltime connection?  How large an equalizer did you use?
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« Reply #25 on: February 15, 2010, 07:13:48 PM »

Lin, your better off with a 120 to 140 amp alternator than with a Vanner both price wise and charging time and I know you like price lol


good luck
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Lin
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« Reply #26 on: February 15, 2010, 08:25:20 PM »

Clifford, I don't know where you got that impression.  Certainly not from my Rolex watch (or is it a Timex.  I get those ex's mixed up).  Anyway, it is interesting to check out the different possibilities.  One thought is that the equalizer puts out 12 volts, so it would seem that it could only charge the batteries part way.  Maybe someone that actually knows could help here.
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« Reply #27 on: February 15, 2010, 10:09:13 PM »

Since grounding seems to be a problem on our older busses is it advisable to run a separate ground wire on these one wire alternators? I presume the ground is through the engine and frame otherwise.

Fred Mc.

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« Reply #28 on: February 16, 2010, 01:00:36 AM »

A single wire alt can be changed/modified to a remote sense alt.  I think that they all can but of course?Huh?  Any alt rebuild-er can confirm the '"if" part.  Pack that 50DN up and stow it in the bus.  In your travels you will find someone that will install it for a reasonable price.  Some of the 50 were anemic in comparison to the biggies.  Maybe 100 amps and that isn't worth reaching for with all the trouble.   BUT, the difference between them is the armature(?) and that swaps out for $60 or 80 the new one is good for 250 amps or more.   Don't hold me to this as it was an incidental conversation long ago and recently I have been having trouble with stuff like where I was married....just kidding but take the hint.  I will post the number of a rebuild-er located here in Eugene that is not convenient to almost anyone but he is a good guy ad will most likely answer any questions youmight have abut auto electrics in general.  Don't have the number on me at this time and no, we arenot related.

Good luck,
John
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