Dual alternators?

[ZR91]

Sent: 3/12/2008 10:48 PM

Has anyone installed dual alternators?

I am hoping to install a second alternator to run a large inverter so the kids can watch TV etc, while we drive.

How would I wire this?

Thanks

Jay

[ClydesdaleKevin]

Sent: 3/13/2008 7:32 AM

I suppose it could be done, but you'd have to find a place to mount it...maybe where the dash AC was mounted, if yours doesn't work anymore?

An easier solution would be to buy one of those flip down DVD players that they use in modern cars and SUVs and minivans...they aren't too expensive on Ebay, you might be able to find one in a junkyard, and they run on 12 volts...you could mount it wherever the kids sit when you travel.
Kev

[ZR91]

Sent: 3/14/2008 8:44 AM

I hope to install a newer style GM 140 amp alternator where the after market a/c compressor used to be(above the p/s pump).  I will use this to power an inverter, and hopefully a fairly large flat screen on one wall(for the kids,of course)

[ibdilbert01]

Sent: 7/9/2008 1:51 PM


A Quick update for anyone who might want to, or is thinking about running dual alternators.

Its amazing how something that sounds simple becomes fairly complex. I've finally got to the point where this project is almost finished.

After much trial and error, I've decided I really like the Motorcraft 3G alternators. There is some talk about the 6Gs being better but I have not tried one, at least yet.

Currently I have a re-wired 250 amp 3G alternator sitting above the stock alternator. I ended up making my own brackets for the 3G alternator. I used 1"x1/4" strapping as bracket material. Making the brackets was fairly easy, and no welding was required.

My water pump has dual grooves on the pulley, one was not being used. I used that groove to drive the alternator. I had a spare alternator adjuster arm that I was able to flip upside down and mount to the water pump housing bolts.

The majority of the wiring is rugged 1/0 welding cable that I bought on ebay. All ends have been soldered on and I used extra heavy heat-shrink w/ the glue inside to protect the ends.

This second alternator is completely isolated from the engine circuit. Its only purpose is to charge the house battery(s), power 12v items in the rig and power the 3000 watt marine grade inverter that is mounted on the floor of one of the now vented closets in the back.

On the dash I have mounted two volt meters. One is for the stock alternator, and the other one is for the second alternator. When the starter key is in the on position, it holds a relay that passes the voltage to to the 2nd volt meter. This way when I turn the key off, both volt meters go to 0. The same relay also powers the fields on the alternator.

In the same closet where the inverter is located is an IOTA transfer switch that automatically changes the rig over to inverter power when unplugged.

Currently the only flaw is the pulley on the alternator is a bit too big. I would like the alternator to spin faster at idle, so I have ordered a smaller pulley. Unfortunately the pulley selection I had for the Delcos will not fit the 3G.

I am very confident that if I add a second battery to feed the inrush that my Air Conditioner generates on start up, this setup will power it.

Last night while the engine was idling, I was able to power some tools w/out any issues at all. So far I am very happy with this configuration but will know more when I travel.

The next phase is Solar on the roof. I am thinking about buying a few Unisolar 64 panels to start off with. I'll keep you all posted when I start that project, probably late fall or next spring.

[Mosin]

Sent: 7/17/2008 7:21 PM

I have been warned by my engine builder and rv mechanic that dual alts will not be worth the HP draw from the engine (and hassle mounting) vs. putting in a larger single alternator. Does anyone know what the largest alt (in terms of amps of course, but also related to size) is that will fit in the stock alt. position?

Thanks, Dave

[ibdilbert01]

Sent: 7/17/2008 8:59 PM

My pulley came in the mail yesterday. I spun off the old pulley with the impact and put the new pulley on. Then this nut put the new nut on just tight enough to remove the threads.

So the quest of the evening was finding a new nut with threads. Ended up running to a dealership and they just gave me a nut they pulled off of a core.

Then after remounting the alternator, I realized now the belt was too big, so off to the parts store again, to buy a smaller belt.

Then, I sat in the drivers seat and with a big grin started up the engine. So far, so good! Volt meter was reading 14+ volts.

And I got over excited and turned on the roof air. In total amazement, the thing started and ran just fine. A quick glance at the volt meter and it was still reading 14+ volts.

I let it sit there for a good 15 minutes or so, and everything was simply fine. I can't be happier with this setup. Its just a nice feeling to know when the engine is running, everything in the rig will work, including the microwave and the roof air.

At this point, I am considering this project a full success with better results than I expected.

This winter I will probably remove the factory alternator and replace it with a 3g alternator as well. I probably will just buy a normal 80 amp alternator instead of an H/O model.

I'm sure this setup is not for everyone, but will be perfect for me. I now have the power to run pretty much anything I want and I have the redundancy of two alternators. If the engine alternator were to fail, I could always do some fancy wiring and be on the road again in no time w/out canceling the trip.

[ZR91]

Sent: 7/17/2008 9:48 PM

This is great information ! I hope to do the same thing very soon.

  Thank-you.

Jay

[olhillbilly31]

Sent: 7/18/2008 10:29 AM

ok i got a question.. any way i put this is gonna sound dumb.. oh well...how are you running your roof air.. on a generator.. but you didn't mention that part... if off the new double alternator setup. I'm interested in that... and since I don't have the ac stuff mounted to the motor i have enough room to run dual alts... maybe i missed something but i just saw i turned on the roof air...


billy

[ibdilbert01]

Sent: 7/18/2008 11:46 AM

Billy, the second alternator is charging the house battery(s) only. Connected to the house battery I have a Vector 3000watt Inverter. The inverter is tied into the fuse panel on the RV using an Iota Transfer switch. When the RV is unplugged from shore power, it automatically starts pulling its power from the inverter.

[Rickf1985]

In your first post you mention a 250 WATT 3G alternator, I am going to assume you mean amps. How do you get one belt to get enough grip to turn 250 amps? I have a military CUCV pick up that I have converted to 12 volts and I cannot turn the 120 amp alternator without burning the belt under full load right after starting.

[ibdilbert01]

Your correct, amps, not watts, I fixed the post and I know better, must of been tired when I wrote the post. 

I did have issues with the belt slipping.  I ended up replacing the crank pulley with a 4 groove pulley and drove the alternator with a mated double v belt.    Used this setup until I replaced the rig with the RV I have now.  It has a reliable generator and I have no need to add another alternator, or I would do it again. 

[gadgetman]

Interesting set up there. I assume you have no gen ? I thought about doing the same thing since I removed the ac belt and dont use the eng ac anyway. But I seldome drive it at night and have 800 watts of solar for the day time. What I did for a easy alt problem backup is I installed a 60 amp cinverter just for the start batt and can fire up the gen and run the converter if a alt issue comes up.

As far as wanting to have a inverter for tv  a small one would work fine line 600 watts to charge laptops and use small electronics that wont run on 12v. The TV you just buy one that has the block in the cord , because those run on 12v just fine. Anything you can run on 12v do so because a inverter will be near 10x the amp draw running it on 110. If you have a 2 amp 110v tv, it will be near 20 amp draw running it through a inverter but only 2 on 12v. You really dont need much to run TVs anymore.