Idea for least costly diesel generator... will this work?

[Bob Belter]

Ahoy, Busfolk,

I have a 12 kw diesel genset which usually is 'burdened' with only a modest load, putting 100 amps x 12vdc charge into my AGM battery farm from my Prosine 2000 inverter.  (About 180 hrs so far, with no signs of any low-power distress).   It does load-up OK with the A/C on.
I am at present building a 'battery charger' for my -01 Eagle, so that it can assume this charger task.  It is a ~~ 6 hp Launtop Chinese diesel  --  copy of a Yanmar.  No longer imported --  Yanmar shut them off, but I now see a similar item on ebay.  (Those Chinese are hard to stop).
The alternator is a 150 amp Delco brushless, driven ~~ 2:1.  There should be plenty of power, with only about 2100 watts load.  I have no plan to try and run A/C  from the inverter.
I converted the engine to liquid cooling.  I just welded water jackets around the head and cylinders.  Seems tight, but I will NOT plumb the cooling into my Cummins M-11. 
I’m setting up the box with air flow so that I can replace with an air cooled engine in the event that this one packs-up.
Sound box, built similar to my 12 KW genset:
 Start with ½” birch plywood, then two layers of 30# roofer’s felt, then one layer of 2 lb/sq/ft roofer’s lead sheet, then two more layers of felt, and then a layer of 1/2 “ plywood.   Sound labyrinths for the air in and out.   Two cheap Kragen mufflers in series.   We shall see how it turns out. 
This technique is very effective and very low cost.  Disadvantage is that it is a bit heavier than more elegant schemes.  Not such a big problem on a bus  --  You probably don’t want to fly it.   
(My 12kw system is so quiet, that if anyone anywhere around is running their genset, you cannot hear mine).  I had planned to include some internal sound absorbent material, but it was not needed.

When it is done, I’ll report on the result.

Enjoy  /s/  Bob

[HighTechRedneck]

I converted the engine to liquid cooling.  I just welded water jackets around the head and cylinders.  Seems tight, but I will NOT plumb the cooling into my Cummins M-11.

Interesting.  I've never heard of anybody doing that.  Please follow up on how it works and how it lasts.

[JohnEd]

I must be missing something.  Gas generators sell for "really cheap" used.  I have a 5KW Onan for $350 and we can talk.  To get their reliability the thing weighs 265 pounds or so.  The things run forever and can be rebuilt.  The rpm is 1850 for low wear.  All gas can be converted to Propane and the Onans have a factory kit.  Propane is better cause the fuel won't deteriorate with age like gas does.

Why are you building something?  Look for a used item....Onan is a safe bet cause they are so indestructible.

HTH

John

[Tim Strommen]

"...I have a 12 kw diesel genset which usually is 'burdened' with only a modest load, putting 100 amps x 12vdc charge into my AGM battery farm..."

I would not expect a 12kW genny to have a problem with a 1.2kW load... (100amps x 12volts = 1,200Watts), except from under-loading.

"...I am at present building a 'battery charger' for my -01 Eagle, so that it can assume this charger task.  It is a ~~ 6 hp Launtop Chinese diesel  --  copy of a Yanmar..."

For reference the "copy" is of a Yanmar L70V air cooled 5.89HP 4-cycle diesel correct?  If so, I have attached the Yanmar power curve or that model (since the Chinese power curve is harder to come by).

"...The alternator is a 150 amp Delco brushless, driven ~~ 2:1...
"...with only about 2100 watts load..."

I have attached a copy of a Delco 12v 150A alternator curve as well.


One thing I should point out is that if you plan on having a fixed ratio, you'll probably need to have a fixed throttle (unless your engine is way over-sized, or you always remember to turn up the genny before you turn on a load).  This is because of the different power curves for the two devices - you'll notice that with an alternator, it reaches almost to peak load by the time it has revved up to 3500RPM (140Amps or 93% of rated output), while the little diesel engine will not get to peak output until its about at the same revs (3500RPM).  Because of the different shapes of the curves, your alternator will demand more amps per rev than your engine will be able to output if you run the engine below max-speed and have a dumb 2:1 ratio - and as the engine slows down due to this over-load, the problem will only get worse (until the engine stalls, or the engine lugs down around 600-800 RPM, giving you about 10% of the output rating - and making a quick death to the engine an almost certainty).

With a 2:1 ratio, the alternator will be demanding about 1.5kW by the time the engine is just starting to generate 1kW (at 1400RPM).  You're in the "lug danger zone" until the engine gets up to about 1800RPM (alternator will demand about 1.7kW while engine outputs about 2kW.

My advice to you Bob...  do a 1:1 ratio.  This should give you more options (and should allow a direct-drive which will improve the efficiency!), and less risk for engine lug.  If you'd like I can map out the power curves as I did for Ray, to illustrate the ratio differences (I can load your engine/alternator choice power values into the Excel spreadsheet I built for him so you can "play" with different ratios to find where you can operate your set-up safely).  If you're dead-set on a 2:1 ratio, add some control logic (a tachometer and a voltage regulator lock-out until the engine is above the lug danger zone).

Without any control logic, or a variable drive system - you are going to have to accept lower output from your selected components.

Cheers!

-Tim

P.S. Hopfully I haven't scared you away from his... -T

[Hartley]

So My SPARE kubota powered 10kw 120/240 Generator unit would do you any good?

Kubota D-950 with Northstar 10 kw head ( belt driven @ 3,600 ) Engine 2,200
burns about 1/2 gallon an hour under full load ( I think?? )

It would be a lot quieter than an air cooled one. And a whole lot less
work at keeping a complicated system working.

I call it my spare or just sort of available if someone is in a pinch.

Email me if you are interested.

Dave....

[pvcces]

One other thought; since the torque load of an alternator and the output curve of a typical engine do not fit each other very well, you could look at just reducing the field current when engine rpm is too low for the power that you need.

That may be what Tim was referring to when he mentioned control logic.

I might be tempted to use exhaust temperature to control the field current; high exhaust temperature would be the result of overloading. If you could get that to work, it would only require a delay after heavy loading to bring the temperature up and reduce the field current.

If the right value was picked for control of exhaust temperature, it should be quite economical and as quiet as possible.

For what it's worth.

Tom Caffrey

[Tim Strommen]

So, I left "control logic" as a broad concept, since there are many ways to operate a genny.

The method that Tom brought up is one way - basically looking at the engine load to regulate the field current (the higher the exhaust temp, the less percentage of the V-Reg requested output to apply to the alternator winding).

Another way, is to wire up an actuator to the throttle in parallel to the field output of the alternator - so that if the v-reg asks for more power out of the alternator (by increasing the field current), the engine is simultaneously asked to produce more power to feed the alternator (by increasing the actuator current which adds throttle).

Another more complicated and complete way is to have Direct Digital Control (DDC) of the throttle and the alternator winding (separate) - where a micro-controller has a table of the output power for the engine and the alternator, and always makes sure the engine is outputting enough power before turning up the demand current for the alternator.

If you go with the DDC aproach, adding a variable ratio drive can have some added efficiency gains (assuming you are already using a belt drive).  This way the alternator can be spun to the exact speed required to generate the load requested output power, and the engine can be spun at the lowest revs that properly support that output load.  The DDC aproach allows the generation system to be run as if there was someone (like an "engineer") constantly managing the engine and power demand and tuning it for maximum efficiency (something my grandpa got paid to do as a Pacifc Gas & Electric power {steam} plant engineer).

Cheers!

-Tim

P.S.  You could use the exhaust temps to see how hard the engine is pushing, or in a diesel check the governor/throttle setting - then put in a current shunt to see how hard the v-reg is driving the field.  With some analog circuitry you could combine Tom's suggestion of pulling back the field current delivered to the alternator and turn up the engine revs then slowly ramp up the field current again. If the field current goes down for a long time this can let the throttle go down on the engine again (with some time integration this can be ballanced fairly well). -T

[Bob Belter]

Ahoy, Busfolk  --  All,

This ~~ 6 hp Launtop diesel IS a Chinese copy of the Yanmar LV70.  Plenty of info available.  It (the Launtop) is rated at ~~2800 rpm, as I recall, not 3600 like the Yanmar).  It works fine at ~~2700 rpm, but becomes rough down toward 2000 rpm.  FYI, it will not come up to speed with the Alternator 'on'  -- not enough torque.  I'll just let it whack-away at a fixed rpm cranking out it's charge.  At present, I only have the integral regulator, but can change to a proper three stage if I decide that I need it.

For anyone contemplating a similar scheme, you MUST provide for the air into the flywheel fan to be shrouded so that it is cold incoming, and the same for the alternator 'in' air. 

I have four ea 205 AH AGM batteries, which I malign by referring to them as AGM meaning 'Alway gonna malinger'.  They don't seem to have the AH capacity stated, but they are still about the same after ~~ five years and 36,000 miles.   My Eagle bus is all electric, and the battery farm runs the household refrigerator and Proheat furnace through the night, and will make a pot of coffee in the morning, and that's about it, with the (unloaded) battery voltage down to 12.0 volts.     

Enjoy  /s/  Bob