Done: 800Ah/24V Bank - SW4024 - DC Genset

[gr8njt]

Thanks to Bill aka Homegrowndiesel, Bruce Knee and Tim Strommen, I was able to assemble the right equipment combination for my DC Power Center Project.

Eight ( 200Ah batteries are inter-connected to the bus battery via "Blue Sea" L-Series isolator.
Two (2) 300Amp Class-T fuses protect the house battery bank.
4/0 welding cable (color coded) is used to connect all the components.
200A of 24VDC is produced by a Mil-Spec C.E. Niehoff alternator spun by a water-cooled 2-cyl Kubota .
The house bank and generator are on individual slide-out trays for easier access for maintenance.

I tested the capability of the set-up off grid right in my driveway. I left the basement freezer, upstaris refrigerator and all the lights ON for 4 days. I also watched a DVD movie everynight on the 36" LCD and the Xantrex inverter was just humming along. The actual DC volts after 4 days was 24.4VDC.

I now realize that I need an "amp-meter" to know precisely what energy is saved and used.
Any users of the Xantrex TM500A?

Just have to figure out how to re-route the Kubota exhaust. Here's some pics of the set-up:

[Tim Strommen]

Looks great Ray ,

      Out of that 4-days, how much Genny run-time was included (or was any required)?  Also, how do you enable your Genny (inside control, or do you have to go outside and plug in a cord and turn it on manually)?  How has your DC-generator setup performed with a low battery (<80% charge remaining), AND a load?  Any pictures of the DC-Genny before it was mounted into the rig? (forgive the questions, most people use AC generators, I'd like to see more "exposure"/coverage of the DC generator method).

Looks very well done!

Cheers!

-Tim

[gr8njt]

Tim,
Out of the 4 days, there was NO outside source of power. No genset and no grid.
I just finished the slide-out and fabricating the genset and alternator mounts yesterday. Although the main electrical connections are in place, I haven't run it yet to charge the bank. I also need time to figure out how re-route the exhaust, how to set the mechanical governor at the desired speed (2K-2500 rpm), how & where to vent the Kubota radiator and  in a hunt for an "Amp-Meter" to see how the batteries are charging/discharging.

The SW4024 has an automatic generator start, however, it is for an AC genset.  So now, I have to figure out how to remotely start and monitor the Kubota by some other means.

It was a brain teaser figuring out how to mechanically join the HUGE Niehoff alternator and the Kubota together. I inadvertently deleted a set of photos I took while putting the gen-set together so as soon as I get it going flawless, I'll update this thread and post more pics.

Thanks again for your help in the electronic/performance analysis of the DC-Project.

[Jerry32]

That seems like an awful large engine to get less than 6000 watts of power. what is the HP rating on it?  Jerry

[gr8njt]

That seems like an awful large engine to get less than 6000 watts of power. what is the HP rating on it?  Jerry

The photo is deceiving because of the angle and perspective.
Internal measurement for a box is W20" x L20" x H22" and weighs 165 lbs.
Also what makes it look tall is the built-in radiator and fan sitting on top of the engine block.
At some point, I plan to re-locate the radiator remotely and inter-tie the cooling system
with the"ProHeat" hydronic system.
This is a Kubota model ZB600C-1 with maximum rating of 14HP and continuous @ 11HP.

[Jerry W Campbell]

Hi gr8njt,
   Good Show. I have a similar size battery bank and I believe
you need more than an amp guage. You need a battery monitoring
system such as the TriMetric 20 20. They will tell you % of charge,
volts, amps, coming , going, more than you ever wanted to know about it.
   When you are out in the boonies you will be making decisions based on
the information available to you. You are now the head engineer for
this new power grid you have created and believe you me you need as
much information as you can get. How long did it take to get them
back up to 100%? It's takes a lot more energy to get back up the
hill than it did to slide down.
   This year we are adding a washer/dryer. We'll see how that goes.
Good Luck
Jerry

[TomC]

As to the exhaust on the engine, the two cylinder, since it is uneven firing, is harder to quiet.  I would suggest using two mufflers in line.  Dick Wright at Wrico, Eugene, Or has Diesel mufflers for your sized engine.  Make sure you use Diesel rated mufflers since a gasoline engine muffler has smaller openings that can clog over time with the soot that the Diesel produces.  I realize the Kubota is a quiet engine to start with (I have the 4 cylinder version of your 2 cylinder powering my 10kw gen), but as far as I'm concerned there is no such thing as a too quiet generator.  I would just put the exhaust through the floor after going through the two mufflers to the side of the bus.  Then when camping can put an up exhaust stack on.  I think it would be real trick if you could put a two speed solenoid governor on the engine.  When the alternator is say producing more than 100amps, the engine would be on high around 2,500rpm (even at that rpm the engine will last a loooong time). Then when it dips below it would slow down to around 1600rpm-like what reefer units on big rig refrigerated trailers. It is easy to do.  You set the idle speed of the engine at 1600rpm, then the solenoid takes it up to 2500rpm.  Then you have 1600rpm no matter what-if the solenoid fails or other.  Glad you've made the system work.  Looks like you did a first class job! Good Luck,  TomC

[superpickle]

Ok  OK, you win the "Too Awsomly Cool " award.. That is Most stupenrusly COOL 

I'll take One please 

[gr8njt]

Here's a pic of the HUGE C.E. Niehoff alternator in relation to the 2 cyl. Kubota:
I have to make further adjustment to both pulleys so I can use 2 belts.

[TomC]

Looks good! Would suggest you overdrive the alternator since it is rated up to 8,000rpm.  With 1:2 ratio, even at 2500rpm on the engine, that would be 5,000rpm on the alternator-still way below maximum.  It is also hard on the alternator NOT to turn it high enough since cooling comes from the internal fan.  Then if you did put in a two speed governor, at 1600rpm you'd still be turning the alternator at 3200rpm.  Good Luck, TomC

[Tim Strommen]

Hi Tom,

    I think Ray picked a simple aproach to his installation.  No kick-up equipment (just a set-and-forget RPM level).  The RPM of the Engine was the design criteria that he wanted to base his install around.  I helped him with an Excel spreadsheet (see screen capture below), which we punched in the performance ratings of both the engine and the alternator.  Then he could pick an RPM he wanted to use and a belt-drive ratio for the setup, to see where that put engine RPM/HP versus alternator RPM/HP (with the losses calculated in as well).  The primary goal of not lugging the engine, yet still getting reasonable power out of the alternator was the point of this exercise.

I believe that with proper planning of air flow - the concern of over heating the alternator can be aleviated.  For example - the diodes that recitfy the AC coil voltage to DC "line" voltage are typically the biggest source of heat.  These are typically at the back of the alternator (the end opposite the pulley), but can also be mounted outside the case of the alternator (this can be done as a "super custom" modification to the alt.).  Ensuring that the diodes get cool air before the rest of the alt is the best way to ensure long-term reliability.  After that, the other concern is the voltage regulator.  Solid-state v-regs don't like high ambient temperatures because they have heat sensitive transistors that control the field coil current/voltage.  If one can move both devices into a separate air passage, this is optimal.

Cheers!

-Tim

[Nick Badame Refrig/ACC]

Hi Ray,

What did you end up with in the final design in engine RPM?

How loud or quiet is the gen-set? I know you had the best helping you design it, "Bill Glenn".

I really wanted to know the end result as far as noise level. I think this is a awsome way to go if it could be quiet.

It's just hard to evict my Onan 12.5 diesel cause of how quiet it is unless there is a better advantage.

Thanks
Nick-

[gr8njt]

Nick,
The 2 cyl Kubota engine maxes @ 3600rpm compared to the 200 amp alternator with a very "steep" output of 60-160 Amps between 1500-2500 rpm then almost flattens out from there with just an additional 40-50 Amps all the way up to 10,000 rpm to be harnessed.  Therefore, based on Tim's spreadsheet and recommendation, I decided to go on a 1:1 pulley ratio.  I am also in the process of finding a method to govern the engine (using a servo) from low 2000 rpm to high 2800 rpm.  At these rpms, this Kubota engine just hums along happily as Bill had tested more than a month ago at Bruce's place. It was not as loud as I imagined.

I hope to contain the happy diesel "hum" in an "attenuated sound box" and I intend to use two (2) mufflers in series (one inside the box and the 2nd outside under the bus) as Tom above has recommended. With this plan, the engine should end up being very quiet to the outside listener/observer.

And yes, Bill has BTDT with DC generation and his experience is priceless in this project.
Anyway, I do not see any reason to evict your 12.5 Quiet Onan if you're not having any problems.

Regards,
Ray

[TomC]

From the power curves, it does look like a good selection.  The alternator will be putting out full output very few times, so mid power will work. 
I have a question-do you only have the one 4kw inverter?  What are you doing for A/C?  With 4kw you should be able to power two roof tops.  But I found that three work the best in over 100 degree weather.  Maybe eventually, you could double your batteries and stack another 4kw to create enough juice to power three roof tops-if you want to. Good Luck, TomC

[gr8njt]

From the power curves, it does look like a good selection.  The alternator will be putting out full output very few times, so mid power will work. 
I have a question-do you only have the one 4kw inverter?  What are you doing for A/C?  With 4kw you should be able to power two roof tops. 

Tom,

Yes, you're right. Tim's electronic genius shows that the ampere demand and supply will almost be even. The inverter's continuous 4K watts will require about 166 Amps of 24V which is about what the alternator will put out at a liesurely engine rpm of 25-2600. Also the availability of a battery cushion of 800Ah@24VDC is quite comforting.

I only have one inverter (Xantrex 4024) and two low amp (10A) roof top Dometic air-conditioners.
My incoming grid power is a 2-leg 50 amp 240V service and I ended up "splitting the legs":
One leg (120V) "passes thru"  the 4024 inverter and also charge the house bank. This is where all the kitchen appliances like ref (2Amps), basement freezer (2Amps), microwave, front lights (mostly flourescent), front outlets and front air-conditioner get their power.
The other leg by-passes the inverter and goes directly to power electric water heater (Marine type 1500W) that will be connected in a loop with the Proheat (24V) system", the rear air-conditioner, rear outlets & rear lights and basement outlets.

I have enjoyed the efficiency of my roof-top AC and after all these years, they still keep my "buns" frozen 
I also had Bruce Knee paint my roof with "ceramic material" to further slow heat convection from the harsh sun.
Hopefully, this will keep my A/C use/demand to the minimum.