Generator Possibility

[Stormcloud]

I have a source for a good 2 cyl water-cooled Kubota engine, presently coupled to an air compressor. Don't know the model of Kubota.

The alternator I use on the bus for OTR charging of the house bank is a 1 wire 200amp alternator that is belt driven off the 8V-71 crank, and supplies power via a 4/0 cable to the bank.

If I were to couple another identical 12volt alternator to this Kubota engine to make a 'diesel generator', there would be room in my "electric bay" (even with a sound deadening box, and permanent quieter exhaust) and I could easily remote mount the radiator. It would give me maybe 15 amps available at 120 volts.

Maybe a larger generator/alternator could be attached to this to generate more power? I'm sure I am not the only one who has done this....has it worked for you? What were the drawbacks?

Opinions welcome.

Thanks!

[bevans6]

What inverter do you have?  I have planned this exact idea for some time.  I really like the idea of a diesel powered DC generator charging the batteries directly and with the house inverter running from it.  I happen to have a 3,000 watt 24v inverter already, so I would do this with a big current 24 volt alternator. 

Brian

[gulfyankee]

I've been thinking on this too. Most buses already have an inverter and some sort of battery bank. Why invest in a regular genset, when u really just need to keep the batts charged? I'll be watching this one.

[Stormcloud]

I have a chinese   3500watt/5500 surge inverter and a house bank total of 7 deep cycle and AGM batteries mixed.
Hasn't given me a moments trouble, and I run frig, microwave, electric water heater element , even the laptop through a brick.

The house system is 12 volt, so I will be installing a 12 volt alternator on the Kubota.

[Slow Rider]

The first rally we went there there was a bus set up like that.  Was a great system.  Owner said the only weakness was the inverter.  If it died you had no power.  During the rally it died  LOL.  He got it running pretty quick but sure did drive the point home......

[gulfyankee]

True enough, but gensets have also been known to fail. Besides, it would be a bit easier to carry a spare inverter than a spare generator.....

[Melbo]

I had the "super bubble" in my genset and it wouldn't keep running til I got it out. No system is 100 percent fail safe. The only downside I see is the AC.  We run two roof tops and the front one from the inverter while driving. So to run both AC's we need a power pole or a generator or in your case another inverter which I guess would be a sort of redundancy. Just thinking and typing here Mark.

HTH

Melbo

[Stormcloud]

I have to go check the engine to get a model number, but the SuperMini series of Kubota were rated about 12.5Hp and were run at 3200-3600 rpm.
If the alternator I choose can put out the maximum amps at half that or less, it should be easier to quiet it.

Hope to look at the engine again tomorrow.

Mark

[Stormcloud]

Yes, it all helps Mel. Likely a few things I havent thought of.

I used to carry a 1kw inverter for when we boondocked for extended periods ( idle current draw was very low) until all the smoke escaped, but I did like the idea of having a spare on board.

Mark

[luvrbus]

Inverters are great but if you are planning on running high draw items like AC the alternator has to be large enough to replenish the draw taken from the battery bank or the batteries will die and it takes a good size alternator to do the job

good luck

[Oonrahnjay]

Mark, I don't mean to sound negative because for some peoples' needs, what you're proposing is an excellent solution.  However, there are some things that you'll need to think about.  You're going to need to provide a fuel supply system.  Also, you're going to have to figure out and make a mounting system for the engine and alternator that locates them securely enough so that they're in line (to not damage the coupling between the units) but stops noise and vibration from reaching the bus.  You'll also have to provide cooling for the engine (I'm guessing it has a water pump built in but you'll have to set up a radiator with fan, etc.; you'll also have to be sure that there's intake air for the engine (best if it's as cool as possible) and also cooling air for the alternator.  And you're going to have to come up with good sound-proofing for the exhaust (pipe and muffler???), the intake air (it can make a loud "wooossh" sucking noise), and the gear for cooling the alternator.
All of this isn't particularly difficult, but it will be necessary.
Also, you have to consider that making enough amps at 12V to provide you with enough wattage for your needs is going to be A BIG LOT of amps (unless your bus is set up with a very Spartan supply of electrical loads).  You're going to have to have some heavy cabling, high-capacity switches, etc. in that system. 
Like I said, nothing that's a real problem to do, but a number of items that will have to be done well to make this arrangement work right.  (I'm thinking that you've probably already considered all this but I wanted to wrap up the issues that come to me for the sake of the discussion.)

[desi arnaz]

I had the "super bubble" in my genset and it wouldn't keep running til I got it out. No system is 100 percent fail safe. The only downside I see is the AC.  We run two roof tops and the front one from the inverter while driving. So to run both AC's we need a power pole or a generator or in your case another inverter which I guess would be a sort of redundancy. Just thinking and typing here Mark.

what is  the "super bubble"

[artvonne]

what is  the "super bubble"[/color]

  I think that was when his gen was air locked with a giant air bubble inside his engine, making it overheat.

  Either way, if we want AC we have to burn fuel. Diesel is more efficient than gasoline, so we burn enough less fuel to offset the fuel cost. However, each time we convert energy there is a loss. I dont know the efficiency of inverters, but guessing they are 10% loss we likely gain nothing over a gas gen if were using it solely to charge and run inverters.

  As the AC units are all AC, and are the greatest power demand, it seems wise to stay with AC power generation. OTOH, if the Bus engine alternator can provide enough power to keep the bank charged, there likely is not a more efficient power generator. Whatever works for you, might be the best option.

  It sure would be nice to have DC A/C compressors and not need to use an inverter.

[jbnewman]

DC air conditioning compressors definitely exist. Some are, I believe, designed for rail mass transit use. Are they prohibitively expensive, or just not marketed and supported for bus use? Is there some secret problem with them?

-jbn

[Oonrahnjay]

DC air conditioning compressors definitely exist. Some are, I believe, designed for rail mass transit use. Are they prohibitively expensive, or just not marketed and supported for bus use? Is there some secret problem with them?   -jbn

I haven't looked in a while but I have a hazy memory in my mind that there is at least one in the Red Dot (otherwise spelled "$$$$$$") catalog.  But don't rely on my memory -- I don't!