12V batt charger/inverter/diesel

[cujet]

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?

[camillitech]

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 

Cheers, Paul

[Mad_Labs]

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

[cujet]

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.

[Geno]

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

[Ronmar]

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... 

[LowGear]

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

[Geno]

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.

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

[Ronmar]

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...

[cujet]

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.

[JLMTECH]



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

[Geno]

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

[BioHazard]

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.

[cujet]

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.

[BioHazard]

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.