I have a Chinese 3.3HP diesel Changfa type engine. (apart at the moment for new bearings). I'm fairly certain that new, high quality ball bearings can be found online for cheap.
I also have a Ford 150A alternator and various 12V batteries including aircraft NiCad's.
I have a new 1500W Xantrex inverter.
My thought was to construct a diesel powered alternator/battery/inverter combo. What for? Dunno. I guess because I can. Is it worthwhile? Or are the problems involved in such a system difficult to overcome?
I have TN property and something like this might be a great way to power a cabin.
Thoughts?
Sounds like a great project Cujet but you do need proper deep cycle batteries for constant charging and discharging. Auto and truck batteries will soon die on you as they're not designed for constant cycling. NiCads are great but they don't work very well on inverter systems because they require higher voltages to charge them which can often lead to the over voltage trip coming in on some models of inverter.
My Trace SW4548e does have a NiCad setting to overcome this but not sure about yours. The capacities can also be a bit misleading as they will happily deliver power at much lower voltages than a conventional flooded lead acid battery. So for instance a 40Ah NiCad may actually have more usable energy than an 80Ah FLA, trouble is you may find some of your lights go very dim :-\
NiCad's cells are also only 1.2v so should be used in tens not six's, or is it 1.5v and should be used in eight's ::) I should know as I have a set but they were never a success on my 12v wind turbine as the voltage was seldom high enough to charge them.
Not sure if and auto alternator would charge them properly either but I'm sure if you're determined enough and the stuff is for free there's gotta be a way ;D
Cheers, Paul
Could work great. One thing is the alt is kinda big, you won't pull anything like 150 amps out of it, I'd guess more like 50. Of course you are going to have to have a 3:1 or so pulley ratio to get the alt up to speed. Don't use too small a pulley on the alt, it makes for more belt wear and more belt tension which equals faster bearing wear. You could put say 4 6V golf cart batteries in series/parallel configuration and this rig should be able to charge that up in good time.
Jonathan
I suppose that I was not clear in my first post.
I don't want a huge battery. But rather, I'd like to use the battery as a buffer and to provide surge load. I don't plan on running the inverter without the engine running, I can idle the engine if necessary.
I just finished the same thing with a 3.5 hp, 3600 rpm, air cooled, Yanmar clone and a 160 amp Leece Neville. You'll probably need to find a way to reduce the alternators output. Even with 2 fully charged batteries the engine would choke immediately with a heavy load. The variac I added towards the end of testing is great for running different loads at different rpm's. After the storm I powered my neighbors 2 refrigerators. I could run the engine at a leisurely 2200 rpm, turn down the field and the batteries provided for the compressor startup surge. When I do put deep cycle batteries on it, it will also allow me to set the amperage for what they need. For instance if I have 2 t-105s I don't want more than 21 amp at 14 volts, 4 batteries, 42 amps, 8 discharged batteries, turn down the field so the engine doesn't choke. I start building my camp in a few days. I hope to use this generator for everything but the 5000 watt unit will be there just in case.
http://www.microcogen.info/index.php?topic=1878.0
http://www.microcogen.info/index.php?topic=573.0
Thanks, Geno
Sounds doable. 1500W @ 14.5V is around 105A + the 15% or so conversion loss in the inverter. That should still be inside the HP limits of the engine, but the ability to limit your field current might be a good thing. For longer term running, you may even want to lower the DC voltage output by the alternator to move closer to a float voltage for the battery. With the right type of voltage monitoring, you could have the engine change RPM to maintain output with increased inverter load/decreased DC buss voltage... this would save some fuel at reduced load...
Hi Gino,
I think if you'd pull your power off opposite corners of the battery pack you'd get better balance and life from your batteries.
Casey
The Changfa will certainly have better surge capability than my engine. The Xantrex probably has 2x surge. I have a 13 amp Ryobi circular saw. It's surge pegs the meter on my 2500 watt inverter for a second. Before adding the variac the engine would give a puff of black smoke when starting it. I could cut a 2x10 but I had to go real slow and make sure not to jam the blade or the engine would choke. If the batteries were real depleted and there was no load on the inverter the engine would choke as well. After adding the variac and setting it properly I could cut normally. The engine would load up to the set point and the batteries would take over from there. I'd say it all depends on what Chris wants to run, pulley sizes, etc. I wanted the ability to run loads greater than the engine is capable of for short periods of time.
Quote from: Ronmar on September 04, 2011, 06:08:44 PM
With the right type of voltage monitoring, you could have the engine change RPM to maintain output with increased inverter load/decreased DC buss voltage... this would save some fuel at reduced load...
Automatic RPM control would be real nice. My engine is quite loud.
Casey, The batteries and box are only temporary and will be used during the construction phase. After things are setup I'll use real deep cycle batteries.
Thanks, Geno
With the engine running all the time, I don't think you would really need a deep cycle battery would you?. Like an automotive application, the battery should never discharge with the alternator maintaining a float voltage across the battery. It is just available to cover the short term surge loads...
So, your engine loads up. Is this due to the alternator being too big? Or is the engine spinning too slow?
I like the idea of being able to vary the field voltage, but maybe I should simply pick a smaller alternator.
Hi everyone,
The setup works OK. I have a similar setup. I have a changfa 170B belted to a 190 amp G6
Ford alternator connected to one trolling battery of about 80 ah. This feeds a 1500 watt inverter.
I run a ref., freezer, TV, and lights when the power goes out here in rural Alabama which is
several times a year. The current draw is about 50 to70 amps with the engine turning about 2000
rpm. The 170B is rated at 4.85Hp at 3000 rpm. The whole set up is mounted on a homemade
two foot high platform cart the size of grocery cart.
The alternator has an internal regulator. When running, the voltage has to drop a little to activate
the regulator to supply 50 to 70 amps. This prevents the battery from being fully charged. When
the engine is stopped for servicing, the battery goes flat (below 10.5 v) in 10 to 20 minutes.
The changfa uses about half the fuel as compared to my gas 3600 rpm 4000 watt generator with
the same loads.
The main draw back for the setup is the need to add cooling water to the hopper every 20 to 30
minutes. Is this typical? I plan to convert to an automotive radiator.
I use this setup to jump start farm equipment. It works well.
I retarded the injection timing slightly. The engine to run a little smoother at partial throttle and
maybe two hundred rpms slower.
Based on Mobile Bob's research, automotive alternators seem to have the best efficiently at
about half the rated output. How does a G6 Ford alternator compare to a truck alternator?
Any ideas to fine tune this setup? Larry
Quote from: cujet on September 05, 2011, 05:23:52 PM
So, your engine loads up. Is this due to the alternator being too big? Or is the engine spinning too slow?
I like the idea of being able to vary the field voltage, but maybe I should simply pick a smaller alternator.
Yes, the alternator is too big. Even at 3600 rpm if I had 500 watts of lights running I couldn't even start the saw. That was before I upped the cable size. A smaller alternator would solve this but then I'd have to worry about heat and the associated reduced output.
Larry, that sounds like a nice compact setup.
Thanks, Geno
I wish I could find a small diesel to make just that. I've been tinkering around with a gas version but never got anything finished. What I like about this setup is that you have two seperate "machines", the engine/battery charger and the battery bank/power inverter setup. If your engine fails you can probably get 12v from the nearest car/truck/whatever in an emergency. It's also great to be able to run small loads off the battery and leave the engine off.
Although if you're building one from scratch without any parts you might want to go with a 24v alternator/battery bank/inverter instead, it would be more efficient and require a lot smaller cables. I want to build a setup with a 3kw inverter but I need to use 350 MCM cable @ 12 volts. ::)
My ideal toy would be a small diesel coupled to a high efficiency 24v alternator with two small-ish batteries to take up the surge and some sort of monitoring circuit that would automatically charge the batteries, then shut the engine down. Start back up again when the battery is low.
Well, I could easily do 24V. However, the problem is that I currently have a Xantrex 12V inverter that I'd like to use. The cables will be quite short.
I'm still not 100% on sizing the alternator or how to prevent engine overload.
Well, in the past it has been recommended to get about 30 amps/hp @12v out of an automotive alternator. That puts you at about 100 amps if your engine is rated correctly.
At 14.5V, I am guessing you are going to need close to around 120A to meet the inverters steady state 1500W output 1500W divided by 14.5V is 103.4A of current, +15%(15.5A) for inverter conversion losses equals 118.9A of DC input to the inverter to put out 1500W of AC...
Now in a perfect world, an alternator should maintain around that 14.5V(typical automotive regulated output 14.5V +/- 0.5V) regulated output right up to it's rated amp output, but RPM and temperature are factors... I guess you need an alternator that reaches it's peak output just before your engine reaches it's HP limit. Or you need a cutout/limiting circuit to match the alternators peak output to your available HP... I have looked a little at alternator regulators, but havn't ever thought about a limiting circuit. Perhaps something controlled by the fuel rack position that switches a field limiting resistor into circuit...
Next question! What about getting the size of the alternator and the RPM correct, so the engine is never overloaded, regardless of RPM?
Obviously, the alternators peak output decreases at lower RPM's. I suppose I should know what the specs are prior to setting up the pulley sizes. Do you guys think this is a valid way to manage the power?
It sure would be nice to slow down the engine when little power is needed. Obviously, the ideal situation is to have the engine speed match the load.
Hi Cutet, Design your project is very interesting, we can "over engineer the h### out of it".
Could give us a few secondary performance parameters?
Engine life?
Fuel efficiency?
Inital cost?
Etc.?
Larry
Engine life? It's a Changfa clone. Low quality. I don't expect 4000 hours. However, I would like to use this to power a weekend cabin. So, maybe 300 hours/year. The thing is apart right now, because the Chinese bearings failed. I'm locating quality bearings for this thing. Plus, I'm balancing the crankshaft, as it had no counterweights.
Fuel efficiency? Dunno. What ever the little diesel burns. I have plenty of waste jet fuel, waste motor oil, used turbine engine oil, etc.
Cost? I seem to be able to source things cheaply. Plus, I don't mind spending a few dollars.
Hi Cujet and Others,
The main reason to have high efficiency for your system is because of limited Hp. Using a
smaller alternator will reduce over all efficiency. A "better" approach is to "gear down" the
alternator. I think a 150 amp alternator is the smallest for your system
My knowledge of alternators is limited so Others may have better ideas. Mobilbob suggests that
the feedback loop of a regulator in the alternator is of minimal power. Also the maximum feed
back voltage is limited. So "gear the alternator" so that the engine can spin the alternator at full
regulator feedback voltage. Then control the maximum alternator output by engine RPM.
My guess, based of comments of Others on this list, is a maximum output of about 1200 watts,
continuous, from your engine. Or about 80 to 100 amps at 14 volts. This matches the (as the
power curves suggest of alternators in general) highest efficiency range. The efficiency falls off
as output approaches rated output.
My version of this system has the alternator geared about 2:1. With the original alternator pulley,
I saw a lot of black smoke (gearing at about 4:1). I am using a polyvee belt off the engine
flywheel to drive the power steering pulley on the alternator. At engine speed of 2000 rpm the
alternator is spinning about 4000 rpm. At maximum engine speed of 3000 rpm the alternator is
spinning about 6000 rpm.
Larry
Well, the alternator speed relationship is a simple way to control the engine load. I suppose it's the most simple.
I had considered a 24V system, but I'm now thinking 12V so I can tie it in to my car's battery too!