Generator Questions

Started by devo, February 06, 2016, 09:43:11 PM

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devo

Hey folks, I've got a few questions some of the experts here might be able to answer.

I've got a bunch of really remote sites that are 100% renewable with Midnite equipment. There are times throughout the year when our renewables can't keep up. It might be that a turbine failed, or the solar is covered in snow, etc, etc. We need generators.

I can't seem to find the right generators at the right price for our purpose. We don't run any AC at all, everything runs on 48VDC exclusively. Our battery banks are all roughly 500aH @ 48.

I've been working on a setup using a Magnum AGS, a portable generator and a AC battery charger. It will work, but its not ideal. The AC-DC conversion is a killer, portable generators aren't designed for standby use, and the whole thing just isn't what we really need.

There are generators out there that will do what we need, but at a pretty steep price. It's hard to justify a $10K genset at most locations. It might only run a half dozen times a year.

Has anyone built a battery charging DC generator? Is it worth attempting or just spend the money for the pre-built rigs? Does anyone know of a small fuel efficient diesel DC generator?

I'd really only need a 3KW generator. The recommended charge current for the batteries we are using is 43A.

Any help you could offer would be appreciated.

mike90045

Robin/Subaru/Hatz makes a 3Kw diesel
http://www.electricgeneratorsdirect.com/Subaru-RGD3300H-Portable-Generator/p1896.html
but it may be hard to find,  They also had a 5Kw version too, which I can't seem to find
I have one of the 3.3Kw (peak) and it's a hard start when below35F, really has to crank for a while before it fires. The cold start kit (glow coil intake air preheater) is pretty pricey and will need it's own battery

I see a generac 5Kw diesel, but something about that brand turns me off
http://www.electricgeneratorsdirect.com/Generac-6864-Portable-Generator/p50700.html

Then you have to locate a good battery charger to run off their alternators.  Finding something with good power factor would be ideal.   <hint to midnight>

But with diesel, there is the cold starting issue, will the AGS system handle preheat ? (air or plugs)
http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV

devo

Thanks for the links.

The problem with AC generators is getting a AC-DC battery charger that can use the available power. I'm currently using these: http://powermaxconverters.com/product/pm3-48v-series/

That PowerMax charger only puts out 18A. I would only be using about 1000W of the generator output. Seems awful wasteful to me.

Since I don't have any inverters, using AC poses a few problems. Higher amperage DC chargers get pretty expensive quickly. I've been reading a lot about a guy in Kansas who developed a variable RPM DC charging generator, but I think that might be a little outside of my current skill level!


devo

The best unit I have found that looks like it would do what I want is by American Power Systems: http://www.americanpowerinc.com/images/APS-75DCH-56.pdf

They don't have a price on the website, but I kinda think it might be a bit expensive.

zoneblue

I know it has some perils, but one installer, i know of, rectifys the 120AC to DC, and whacks it into a classic 200. Hes an old wind guy, so has all the honking big rectifiers laying around. Im not sure of the details of how he does it, there must be something to give it a mpp to work with, maybe some caps too. He uses the cheap 3kW gensets for this, and just throws them away when they die.
6x300W CSUN, ground mount, CL150Lite, 2V/400AhToyo AGM,  Outback VFX3024E, Steca Solarix PL1100
http://www.zoneblue.org/cms/page.php?view=off-grid-solar

TomW

#5
Off the wall, D.I.Y. from a guy who has loud teenagers next door  and can't sleep :

AC gen>>AC motor>>big vehicle alternator >>batteries?

Sort of an AC >>DC rotary converter  ;D

You likely can fine tune that to suck every watt out of the generator [probably lossy].

All off the shelf stuff pasted together.

Just spitballing from the peanut gallery..

Tom
Do NOT mistake me for any kind of "expert".

( ͡° ͜ʖ ͡°)


24 Trina 310 watt modules, SMA SunnyBoy 7.7 KW Grid Tie inverter.

I thought that they were angels, but much to my surprise, We climbed aboard their starship and headed for the skies