first small diesel generator build

[photon_trap]

I am beginning my first generator project around a Kubota EB300 (6 HP Diesel) and ready to begin shopping for a suitable generator head. The primary use will be to charge a small bank of deep cycle batteries. (as a backup)  Would I be best off with an AC generator such as an ST or a heavy duty automotive (truck) type with 12 v (ish) output. I realize both would have to go through a charge controller of some type.

I need advice as to the advantages and disadvantages of each (and any other) options and what other issues are relevant to my decision

TIA!

Jeff A  (newbie to diesel generators but mechanically competent)

[miket]

I use a DC alternator.  It has been through two iterations. 

first was a 12 volt, 160 amp,Leece Neville 2500JB  and Xantrex controller, then a 24 volt, 250 amp Balmar alternator and ARS 5 when I when to 24 volts.

It's nice and compact and thrifty on fuel. 

Been running about 4 years and am thriilled with it.  My fuel tank is too large though.  For the amount I use it The tank will hold about a couple years with of fuel.

The 12 volt version charged the 12 volt 840 amp hour  bank just fine  from 80% SOC to full in about 3 hours.  Initial rate of charge 90 amps or so.

Charge time for the 24 volt bank  takes about the same time, amps corresponding lower because of the 24 volts.

I always charge till it indicates "Float" on both the Balmar and my Trimetric 2020 (about 4 hours). The Trimetric will indicate less than an amp of charge at that point.
In both cases, call it  2 quarts per charge.

The B300 is a great unit.

mike

[SteveU.]

Excellent report and feedback miket.
Confirms what I told a system developer friend. The batteries will only load his 5000 watt DC capable system with what they needed. To fully load it up he was going to need an expensive inverter or ganged cheapo's and some live AC demand loading.
Thanks
SteveU.

[Tom Reed]

One consideration is if you need to run 12vdc loads only or 120vac loads too. If there is a need for 120vac support an ST type head will give you the option to run loads directly off the generator or use an inverter/charger to run your loads.

[photon_trap]

Thanks Guys -  Being new to this stuff I am not clear on battery setup.

First let me briefly explain what I am working towards. The plan is to have sufficient battery power to run my garage essentially "off grid" with solar panels and possibly a small wind turbine operating to keep batteries topped off. There's little use of garage all week while I'm at work so this will make it easier to maintain charge. The EB300 generator will be a backup to the system to provide charge as need in excess of solar/wind input. This will give me reliable power to keep things running in the event of power failure in the house/neighborhood  .... or worse

sooo, my first question is about batteries - what is the advantage to arranging batteries in other than 12 volt configuration (meaning 24 or 36 volts or greater (?) Seems I would want to decide on this now to avoid do-overs - ha

Thanks
Jeff A

[Ronmar]

Watts are watts regardless of the source.  Power in watts is equal to current times voltage, or P over I times E.  If you know any two, you can solve for the third.  1000W from a 12.5VDC source(1000 divided by 12.5) is 80A of current.  From a 25V source, that same 1000W only pulls 40A. From a 50 volt bank it is only 20A.  So a 48V system can use wire 1/4 the diameter of a 12V system delivering the same output...  High power 12V systems require MONSTER sized cables and connections and are very limited as to cable length due to cable resistance losses.  If I were building a battery-inverter system I would plan on 48V, and settle on no less than 24V...

You will need a controllable regulator.  From what I read of Mobile Bobs testing, an auto alternator sized to run near the middle of it's available capacity range can reach efficiencies rivaling that of an AC to DC charging scheme once all the conversions are factored in. I would guess that not overloading/overheating the alternator plays a big role in this peak efficiency point.  The alternator configuration will probably be simpler though...  So what you need is an alternator that reaches it's peak efficiency point at around your engines sustainable horsepower output level.  You will then need a regulator to control the alternator to keep the alternator from overloading the engine.  One of the beauties of using the auto alternator is that you can also couple an AC generator in, so you have direct AC generation as an option...  Since you are already planning on solar/wind generated DC into the inverter to maintain the batteries, the only thing the alternator needs to really do is to maintain it's output at the peak efficiency point for the alternator untill the generator is not needed/batteries topped up.

Good Luck with your project.

[photon_trap]

Thanks Ronmar for your explanation.
So, taking your advice, I build a 48 volt system, does the charge controller increase the voltage from 12 0r 24 volts (from the solar panels and/or alternator) or is there such a thing as a 48v alternator?

Sorry for the basic questions - I realize this is probably off topic

Jeff A

[mbryner]

Good luck finding a 48 V alternator at a decent price.   That's why some of us who have 48 V battery banks use a ST generator head at 120/240 V AC and use a MPPT charge controller to charge the batteries and have 120/240 AC backup from the generator as well.

Marcus

[Ronmar]

Jeff, if you look at the specs for the inverter you are thinking about, it should have the DC voltage input specs required by it's charging controller. This will also determine how you wire in your solar panels. 

Marcus, Yes that is one of the challenges with 48V, but an inverter used to taking in solar usually has a rather large acceptable DC input range, which makes it a little easier to be creative without as much elaborate control/regulation required.  Another option besides an AC generator could be a large frame 24V alternator, with a regulator configured to drive in that 48V range...

[miket]

I run my eb300 at 2200 rpm which is both peak torque and lowest specific fuel consumption point. torque is king over horsepower in this case.

I use a 2:1 gearing for the alternator so it is spinning at about 4400 for good cooling and output.  My alternator is a medium frame Balmar 24 volt 250 amp unit so it is not working real hard.  I got a great deal on  the alternator and controller on fleabay saved almost a grand.

I run 48 volt PV arrays and an MPPT charge controller to get an earlier start on charging due to my compromised insolation situation lots of tree shading. By doing so I get usable charge about an hour earlier in the day.

My leads off the alternator are 4/0, 105 c, 600 volt, rated   copper.  Leads are as short as possbible.

I used a 13 rib micro v belt and QD  sheaves (taper lock) from McMaster Carr.

My EB300 was originally equipped with a hydraulic pump and that was all deep sixed and the flywheel drive flange now holds the QD mounted sheave.

mike

[hal]

Mike

Can you post a picture of your belt and pulleys?

Would you mind posting the part numbers?

Thanks

[photon_trap]

Mike, (or anyone) How does one get from 24 v (alternator output) to 48v for charging batteries? Or, are yours arranged to 24v config?

I'd love to see pics of your setup as it sounds similar to what I am building

Thanks for the help!

Jeff A

[photon_trap]

Never mind Mike, I see now you did post pic !

Doh!

[Henry W]

Mike, (or anyone) How does one get from 24 v (alternator output) to 48v for charging batteries? Or, are yours arranged to 24v config?

I'd love to see pics of your setup as it sounds similar to what I am building

Thanks for the help!

Jeff A

Hi Jeff A,

The person that can help you on this is mobile_bob. He has been working on converting Leece Neville 24V alternators to 48V.

Henry

[Ronmar]

I guess we should have posted a link to Mobile Bobs White paper on 24-48V alternator testing...
http://www.microcogen.info/index.php?topic=157.0