Micro CoGen.

This is a paper i have been thinking of putting together and publishing for several months now
and up to this point i had no avenue to use to publish it that i felt would be around for any length of time.

This attached paper is not for everyone, many folks will have little or no interest, however
those that are looking toward the use of batteries and inverters, or building an inverter/generator should
find this paper useful.

I welcome constructive comment and of course questions, and would be willing to argue points of contention
as well should anyone feel the need to do so.

Not knowing how to copyright this work, i would only ask fellow forum members to keep and use for your own benefit
and not copy/paste this work to other forums, i have no problems if anyone wants to link back to here from another forum
i just don't want this taken elsewhere.  

This work comprises many hundreds of hours of research and development over the course of several years, every effort
has been made to design a suitable alternative using off the shelf parts to accomplish the goals set out for controlled battery
charging higher voltage battery systems efficiently. I have a significant investment in test equipment, many different controllers
by various manufactures and stacks of alternator cores that i have worked with to arrive at as simple a solution as is possible
and still get a quality result.

nuff said

bob g

excerpt from the paper

ABSTRACT

   The typical offgrid home will often be powered by various alternative means, with solar, wind,
sometimes hydro being the predominate prime sources of electrical power. In order to use these alternate source of power over the full range of a day batteries are the most common method of storage and buffering the power generated to provide for the home loads over the hours when either the wind is not blowing or the sun is not shining.

   In order to assure proper charging for longer periods of time that there is no power generation available,  the most common approach is that of a standby generator. Standby generators can either provide for the loads or provide for battery charging or as is most common a combination of both.

   Generator systems that provide for both loads and battery charging most often use either the built in charger of the inverter system or a standalone battery charger that is simply plugged into the generator. In fewer cases the system will have a generator to provide for the loads and also an automotive alternator to do the battery charging. This paper will explore the use of both methods and illustrate the overall efficiency compared to a new approach of the  "reapplication" of an automotive
alternator that will be shown to operate at higher power density and with dramatically higher efficiency than either of the prior methods.

   This paper will investigate if the typical automotive alternator herein referred to as the clawpole
alternator can be operated at a much higher output power level and at dramatically higher efficiency.
A brief history of the machine will be presented, its theory of operation, what is known about the machine when used as designed, and what can be accomplished by changing the machines operating parameters.

   In order for the reader to fully appreciate what is presented in this paper he will need to effectively forget everything he thought he knew about the automotive alternators theory of operation, and he will need to also put out of mind any assumptions based on prior experience or what has been published by the original manufactures of the machine.

   While the machine was built by and for the automotive industry our intended use is not concerned with the constraints place on it by that use. For our intended purpose of charging a battery bank at a fixed speed the machine should simply be viewed as any alternator might be, the only similarity is visual  to its automotive counterpart.

for complete text download attachment (available only to forum members)

Hello Bob,

I liked what I read. Reading it on paper gave me a better understanding on how higher efficiency can be reached. as you know I have been trying to decide what my next project would be.

It looks like this it the perfect project for the small Cat engine.

Henry

Thanks Henry:

one hopes when he gets heavily into research/developing and then testing something
that he thinks might be useful, will indeed be useful to others?  who knows?

with ongoing discussions relating to inverter/gensets and offgrid use of battery inverter systems
it just seems very reasonable to me one would really want to look into how to do it as efficiently as
possible.

the difference is efficiency is not a small number that would make a significant upfront expense hard
to justify, the difference equates to in some cases enough fuel savings in a year or two to pay for the
total generation system, engine and alternators

there are a hand full of folks that have been following the testing progress, and i just figured that a paper
needed to be written on the subject. there is a lot of misleading info out there, and to my knowlege no one
that has explored this method.

hopefully we pickup a few more members because of the paper?

that would be a good trade in my opinion

bob g

Hi BobG.
I read your paper too.
I liked your keep it simple concept. You were right; I did have to set aside my automotive preconceptions to appreciate this.
Thanks for the early claw pole history. I do recall seeing late 50's, early 60's big heavy claw pole Leece-Neville emergency service vehicle 3 phase claw pole alternators that were pre-solid state diode using a remotely mounted "fish plate" style battery charger rectifier plates. I cannot remember the proper rectifier active material name. They did have to use a generator type cut in and out relay do to the rectifier plate reverse current power bleed.

To achieve 42+ volts output do you think the rotor coil winding will need resizing? Did you intend to up the buss rotor supply voltage to 24 volts to get these higher output voltages?

I have been told the reason for the 42 volt standard was to keep the charging voltage below 50 volts to keep Union shop equipment users in many areas from running afoul with  Unions rules requiring over 50 volt systems to have only Certified Electrician service. Urban myth, you think?

Regards
SteveU.

Wonderful paper, Bob G!  I had no idea that the claw pole design had seen use in serious power production, and that the efficiency could be so high.  It makes rotor cost low, and also is a design which is well suited to high rotor rpm.

When I eventually get around to wind power,  I think I'll take a close look that the "Mallard" made by a local area craftsman. http://mikeswindmillshop.com  They are using an truck alternator frame, rewound and rebuilt.  I friend has several of these, in service for the last 6 years. He's very impressed with the performance and reliability.  Perhaps with custom windings, I could get some output suitable for my 120V battery bank.

Thanks Bruce and Steve:

Steve:

the excitation voltage never goes over ~10volt dc at 3.5amps at 100amps output and 28.8volts
there is no need to overdrive the field which would only serve to build heat and reduce overall efficiency.

because of the isolated and seperate excitation system used we maintain the 12volt rotor as is without modification
this was a huge benefit to the overall concept.

i have spent well  over 25 years rewinding stators, overdriving rotors, swapping parts and everything you can imagine
trying to find the holy grail with mixed results, usually i could get the voltage, but always ended up making more heat
and took a serious hit in both output amps and overall efficiency.

it wasn't until i started to really dig into all the theory and math that is used to design these machines that it occurred to
me to take a look at the automotive alternator (in this case the 110-555jho) as simply an alternator without concerns about
it being useful in an automotive application that things started to take on a different light.

when you seperate the excitation from the machine, and allow the unit to operate freely at your target voltage you end up
with a unit that will do what you need it to do very well, but
the end result after all is said and done is the machine is now worthless for automotive use, such a machine would not even begin
to charge until you got up to mid throttle and above, making it not at all useful for automotive use.

i figured that we need an alternator to make 28.8volts and do it well, with common parts at a specific speed, because our stationary
engines operate at a fixed speed anyway.

btw, i think the rectifier you are referring to from the 50's were selenium rectifiers they looked like a stack of metal plates
with a center bolts running down the center sort of things
and stunk like hell if you short or overheated them,, i find out now 40 years later the smoke off of a selenium rectier is some deadly
stuff,, who knew?

lastly because of the isolated excitation the project x alternator will make ~130amps at 57.6volts (48volt charging) and
still remain under 12volts for the field.

that is probably the biggest thing to get past because typical automotive alterantors rotor coils are matched to the output voltage
ie 12 volt coil for a 12 volt system, 24 for a 24 and 32 for a 32,, and who knows what they plan for the 42volt systems?

we can do anything from a 12volt excitation within reason, certainly 12, 24, 48, 60 and up to 480v is possible
much like the big boys that use 240vdc excitation on multikvolt output generators. 

i like 12 volts for excitation because we have a lot of rotors to choose from, large numbers of regulators to work with,
and often times a 12volt starting system in place on the machine to take our excitation buss power from.

bob g

something came to me after reading some text on alternator testing, increasing alternator efficiency,
and other concerns relating to high output alternators being driven together from a common prime mover.

when i am testing the st head for BSFC (gr/kw/hr) i have the excitation current shut off on the
24volt alternator, so there are no core losses from the alternator being attributed over onto the ST head

however, i forgot to disconnect the excitation to the ST head while doing the same BSFC on the 24volt
alternator so the core losses of the ST are being attributed to the 24v alternator.

this is flawed and skews the numbers in favor of the ST head, by perhaps as much as a 2 percentage point
spread.

if this is the case, which i suspect it is, then the reapplication of this alternator for 24 volt nominal operation is
more efficient than the ST head by 1 to as much a 2%

more testing will confirm this

what is interesting to me is this
if the numbers support the 2% skewing is the case, then the 24volt alternator is more efficient than the st head
by 2 percent, and
the 48 volt "project x" alternator should be between 2-3% better than the 24volt version
for a total of as much as 5% more efficient than the ST head.

this gets me very close to parity for produceing power that could be fed into an inverter and have very close to
the same cost in BSFC in gr/kw/hr as what is produced by the st head

whats important here is the resulting power would be dead on 60hz, no flicker with superior voltage regulation, very
low harmonic distortion , basically very clean power.

and that is the holy grail as far as i am concerned

it would appear that i am very close to parity, close enough to push onward to try and attain this goal.
which btw going into this i would have never expected to get within 10 percentage points of the ST head.

we are inside the moat on this one and storming the gate.

bob g

Very very interesting! Thanks for all your work and the write up Bob.

Bob, this is mostly over my head, but why couldn't the exciter alternator be of the permanent magnet type?

the exciter can be any dc power source that is a stable 12volts dc nominal, beit battery that is charged by
a wallwart charger, a pm alternator that has some form of controller to stabilize the output voltage to no more
than ~15 volts, or another standard wound field alternator such as even a very small lawnmower alternator such
as one that is part of the engine charging system.

the only reason i used the second 110-555jho was because it was already mounted and will be used for heavy charging
a 12volt battery bank that other things will be powered from that need 12vdc power.

bob g

Hi Bob, I've been following your experiments closely and very much look forward to some info on the 48v modification. I now have a 110-555jho, a 48v battery bank and a 48v, 5.3kva UPS to plug them into. I'm hoping to be able to use a remote rectifier as the batteries will be 75' away. I also want to use an Outback Flexmax 60 because of its versatility.

My second application of the alternator/controller will be to charge batteries at camp. Probably no more than 4 t-105's at a time @ 12v. For this I have a 4hp air cooled Yanmar clone and an old generator frame to mount it in.

Another thought I had (your idea perhaps??) was to rectify my current AC and feed the Outback with that. I believe that will give me 170VDC (120x1.41) The only problem I see is that the DC voltage will be higher than the Outback will accept. Is there an easy, efficient way to reduce the DC to 140v or less?

I very much appreciate the research you've done and your willingness to share it.

Thanks, Geno

Geno:

let me clear the air a bit,
the idea of using the outback mx60 was not mine, the first talk of using such a scheme was first postulated
by Bill Rogers a few years ago, and the first real application of its use with an engine driven generator was the aircore
alternator that is mentioned in another thread here on the forum.

as for reducing voltage to the point that the mx60 can handle it, perhaps a special built regulator could be made
to control the ST voltage output to something on the order of 90volts or so, allowing a bit of overshoot and still stay
under the 140volt dc limit of the mx60?

what i don't know is how stable the st head is at lower voltage, but with a good regulator that should not be a problem.
however i think i might suggest some sort of voltage clamp to catch any load dump situation that might cause the voltage
to overshoot or spike if a load was dropped quickly, so maybe some sort of MOV?  there are electronic guru's like BruceM that
are better at addressing that concern. Actually i think he is working on a 120vdc system, so he may well have a very good
regulator design already that can be used to do what you have in mind.

another option is to design and build a buck converter that can handle much higher voltages, perhaps as high as 240 x 1.41
or 338 or lets call it 350volts or more. then you can use the st head at its full capacity? just a thought.

as for a remote rectifier you must use some fast recovery high power rectifiers, such as the press mount automotive types
the 600 plus hz coming off the alternator will lock up a standard set of rectifiers into full time conduction, making a very effective
electric brake for your motor. probably hard on batteries too, and likely really hard on the mx60

fun stuff huh?

bob g

Standard recovery power diodes should be fine at 600Hz, I think. Fast recovery is more of an issue at 30KHz and above (switching power supplies).

For my 120VDC battery bank I'm using 240VAC (regulated by my AVR) as input to two toroidal transformers (surplus, otherwise one to my specs would suffice), with their output going to some zero cross switched capacitors , then a 1100 watt toroid core used as the primary filter choke.  The caps switched in before the filter choke allow the battery bank charge controller to adjust charge current.  I can also switch windings on the transformer for an even wider range of applied voltage and current.  I've attached a schematic for the capacitor switcher.  This is a novel and highly efficient linear charger, with digitally controlled output regulation.  It avoids the huge EMI emissions of a switching power supply, which is why it was important for me. It is my original design, and I've never seen such a thing before, but in electronics there's not much that really new.


It would be feasible to regulate the ST output to match my battery bank, but since I'd have to use a transformer anyway I'd rather not.  I can then use the excess AC power capacity while battery charging.

It would not be hard to modify either of my AVR designs to provide regulation at some other voltage, or a pair of voltages.

Bruce M

well from experience a common 3 phase bridge recifier is made to operate at 50-60 hz, many start to go into
avalanche at 100 hz, and most will certainly do so at 600hz

from the manufactures engineering staff i spoke with, an i can't remember which one just now, they told
me most common high power bridge rectifiers are made to operate at 60hz in this part of the world and will
not work at 600hz, however they did refer me to a manufacture that does make fast recovery rectifier bridges
that can tolerate 600 hz at 150amps

perhaps it is the combination of high current and 600hz, that causes a problem,, i don't know.

but they certainly make  for converting your alternator into a very effective electric brake!

the black smoke sure rolls off the changfa when the rectifier faults and goes into avalanche
interestingly the bridges i have don't seem to be harmed by it, but they don't work for what i need either.

:)

as for regulating an st head down to 48, 24 or whatever, you are still limited to the stator winding current capacity
unless you regroup the stator pole windings and parallel them then you can get a pretty decent output for a 48volt system
anyway.  otherwise ~40amps at 48 volts is ok, but not very much for a 24 volt system from an st5 head, it would seem
to me anyway.

bob g

Sorry Bob,
I didn't realize you were talking 150 amps.  I know nothing about diodes at that much current, except to avoid it.  :)

Bruce:

no problem sir, i too would have expected no problems
and i really didn't have any problem until i exceeded about 100amps on my way to 130amps
at 28.8 vdc
thats when my rectifier bridge which is rated at 1000vac PIV and 150amps started to get very irratic

it seems that at about 75amps i could count on it working as designed "most" of the time, and as
you know "most" of the time is not good enough.

from my vague memory my thinking was i would not need fast recovery diodes until i got to many khz
and so i just assumed i got a faulty surplus unit, i ordered two of them so i tried the second and got similar
results,, that is when i called the manufacture and asked for their engineering dept.  thats when i learned
about high power bridge rectifiers for the most part are rated at up to about 100hz before they get flakey.

who knew?  i just figured a bridge rated at 1000 volts and 150amps per diode was good enough for my use
luckily it didn't damage anything, didn't seem to damage the diodes either.

upon looking further they make stud mounted unit with the 4" cable comeing out the end, single power diodes
rated at anywhere from 50-1000volts and 75-150amps and beyond that are fast recovery diodes, apparently they
are used in some sort of high frequency rectification apps, i don't now,, i think i have enough of both types
to build a nice bridge if it comes to me needing one.

so far i have figured a way around needing such a beast with some aftermarket automotive press in diodes
rated at 200volts and 75amps each they seem to be sufficient to hold up for 57.6 volts DC and ~130-150amps
collectively in the oem heat sinks

bob g

I'm very happy to learn from your experience.  (So much cheaper and less aggravating!)

I never would have found out as I usually go for gross overspec (2-3x) on power components.  Cowardly but cool and covers sins in design and fabrication.

"Quote from Bobs white paper.
Next we will adopt an architecture from the alternators big brothers, that being separate
excitation of the field by a separate belt driven exciter. We usually have a 12 volt electric start on our engines, and as such must have an alternator or other charging source for charging the starting battery. This starting battery system will be the backbone of our excitation buss. We now have a 12volt excitation source for our 110-555jho (reapplied 12volt machine) so that if we were to turn the machine at a sufficient speed it would begin to charge. Because its cut in at 12volts was approx 800rpm, its cut in speed for 24 volt operation would now be approx 1600rpm. For reasons explained later we shall set our design speed to ~4500rpm, which is well above the requisite 1600rpm needed for cut in at 24volts. Such a basic system would work to charge a 24volt bank "if " one wanted to babysit a field control rheostat, but this is both ineffective and can be either injurious to your batteries or dangerous, so
End quote"

Some of you have been following my " Portable battery charger" thread and I'm ready to gather ideas to bring it to the next level. That being proper, 3 stage charging of a battery bank using an external 3 phase rectifier and my Flexmax60.

Goal:
To be able to charge a 12-48vdc battery bank at whatever power/voltage/hz the various components are capable of. Keep in mind I'm not looking for enormous amounts of power here either.

My question is:
Could I do what I think Bob states and use the starting battery as an excitation source with a field control rheostat to control the output voltage of the alternator? If I can do that I can then fine tune the alternator output to provide the most efficient voltage to the rectifier/Flexmax for whatever battery bank voltage I'm charging. From what I've read the flexmax is most efficient with an input voltage close to, but above battery equalize voltage. There's a table in the manual.

By the way, I'm a bit over my head here so if my idea will smoke something or lead to ridiculous inefficiency I apologize in advance.

Thanks, Geno

does the starting battery get its charge from the engine's integral alternator?

if so you can use the starting battery as the excitation power source, and would be in keeping with the suggested method
in the white paper.

you will need to disable the internal rectifier bridge, because it has avalanche diodes that will clamp at about 30volts,
which leads to the alternator becoming a massive engine brake, lots of smoke and a burnt belt.

the next problem comes in what to use for a rectifier, it will have to be fast recovery diodes, those typical for use on 60hz
will not work for this duty because you will likely be anywhere from 400-600hz, the common diodes will go into full time conduction
and not rectify, and you end up same as the prior example, smoke and squealing belts

these are the major hurdles to overcome,

if you are content with a 24volt system, the oem rectifiers will just barely get the job done without going into avalanche provided you
use heavy enough cables so that you don't have anymore voltage drop than necessary, any drop limits the available charge level
before you trip into avalanche.

that is the short answer, if we have more info on your end use maybe we can determine the best approach to get you there.

bob g

i am familiar with the niehoff alternators, at least the large coach units that are 24volt nominal and ~300amps
bloody expensive units that are not for the casual diyer in my opinion.  but if you can afford one it should be one
hell of a unit.

as for remote mounted rectifier, if you can remote mount the oem unit then you will be ok, if not
perhaps you can get a set of replacement diodes for the unit and remote mount them in a heat sink
with fans?

if that is not an option you will need fast recovery diodes, because most of the really nice heavy duty units
are rated for 50/60 hz operation and will lock up into full time conduction and not rectify, don't ask me how i know
this, suffice it to say it cost me a very expensive balmar controller.

what battery bank voltage are you wanting to work with? and
how large a bank in amp/hrs, and of course
will it be flooded lead acid, agm or some other technology?

btw, thanks for the kind words, speaking for myself "i am no guru" but i too am looking for the holy grail of dc battery charging w/cogen
and i think i am a lot closer than some of the commercial suppliers in that regard, probably because i have less concern for profit margins.

as for the aura-gen
i am only familiar with the product from their literature, and am very familiar with the design
it like everything else under the sun is nothing new, it is an axial machine, likely very expensive
and probably does what they claim, however
it looks to be targeted toward military use and as such has a lifecycle measured in perhaps hundreds of hours
as is the case with most military and aviation stuff, where weight and size take a front seat to longevity.

of the two units, the neihoff is the bullet proof one that will likely run forever with very low maintenance.

in my opinion of course, ymmv

bob g

Yes, the little diesel has an internal charger for the battery.

I remember reading the previous posts about the diodes going into avalanche and causing problems.

There are a bunch of new listings for 3 phase rectifiers on ebay. I don't know what frequency they can handle though.

My potential uses are
1)   (Little engine) At camp to recharge 12 volt batteries but I can probably get away with the stock alternator there if I'm careful.
2)   (Little engine) At home to recharge a 48 volt bank with a remote rectifier if the Lister is down.
3)   I may get another 110-555jho and hook it up to the Lister with a remote rectifier to charge the 48 volt bank. This would also give me a more powerful, CHP ready prime mover and another option if the st head is down.

I guess I'm just exploring the possibilities and I just can't stop tinkering with my stuff.

Thanks, Geno

I think that the "Stack Rectifiers" will yield disappointing results.  Simple radio shack floor sweeping diodes will likely out perform them.
Modern schottky diodes are the way to go, with proper voltage and current ratings.

I can't say much about the "stack" rectifiers as I haven't seen any specs or prices.  Custom rectifiers would not be something I'd be ordering for my own use due to cost. 

Schottky diodes are great, but you want plenty of headroom on the voltage rating.  Schottky diode forward voltage (loss and heat) is reduced with a lower maximum voltage rating, so it's tempting to cut it close, but if you do, you'll have to thoroughly evaluate the transient (spikes from switching) situation and perhaps add some suppression circuitry...all it takes is one over voltage spike and poof, your Schottky diode is now converted to a piece of wire (shorted).

I've seen one solar PV charge controller that uses a (too) low voltage Schottky diode to save cost on heat sinking. Just the inductance of the leads running to the solar panel is enough to generate spikes when switched off to fry the Schottkys. Within a few days of installation, every unit's Schottky diode fails.  In this controller, that means a much higher night-time drain than there should be, both from circuitry that didn't get shut down at the charge controller and because of PV night-time losses. 

The amount of commercial gear with poor or "fragile" design is pretty depressing.

BruceM

your project presents some real hurdles in my opinion

getting to the high 60% in efficiency with the alternator is a testament to the quality of the neihoff product
however working at 12vdc nominal is not without serious compromises especially with large distances and high currents.

i understand now your desire to remote mount the rectifier, but i would pass on the selenium rectifiers for a couple reasons
one is efficiency, the other is the toxic smoke that is released should you have an overload or short. only recently have i found
that the selenium smoke is toxic, i remember well that acrid odor as a kid experimenting with those things,, maybe that is why
i am so strange today??  :)

here is a possibility for you that might just do what you need with higher overall efficiency

check with balmar, and see if their mc612 will handle the field of your alternator, it should because it can handle the field of two
large frame alternators easy enough.

remove the rectifier from the case of the alternator,

attach three transformers from some salvaged ups systems like the apc units,
they are ~120/24 volt units, set them up as delta connected first, then maybe change to Y connected
to see which will get the result your after.

attach the regulator sense line to the battery bank,

rectify the stepped down voltage of the transformer pack,  and feed the rectified current to the battery
bank

your going to have to work with monitoring the field current, so place a 10amp fuse in the field wire
from the regulator, so if it over currents it will pop the fuse and not your regulator.

the goal is to spin the alternator up to a speed where it is making something over 60volts or so
let the transformers drop the voltage to the needed 12volt nominal for rectification and battery charging.

from what i can determine from the manufactures of transformers, 60 hz units can be used up to 400hz
with little penalty in efficiency, and up to as high as 1khz before things start to fall off significantly.
3 manufactures have told me that 500-600hz is ok with most 60hz transformers.

such a system if it were to work, would be pretty cool in that you could run your power from the alternator
on maybe 8 or 10 gauge wire, step it down to be rectified and charge at 12volt nominal, and the sense wire
being connected to the battery bank will tell the balmar what is needed to attain the charge level you program it for.

the balmar really doesn't care about how high the stator output voltage is, or that there are transformers involved
it just wants to see two things, a nice 12volt supply, and a 12volt nominal sense from the battery.

my bet is such as system would get you over the 70% barrier and quite possibly into the mid 70's in efficiency.

this scheme is nothing new, delco as well as leece neville both built piggyback transformer rectifier packs so that
a 12volt alternator could charge both 12 and 24 volt simultaneously

all we are doing is altering the voltage parameters, the underlying theory of operation is the same.

having said all this, it might be that a smaller alternator could be used and get you up to 250amps at 12vdc nominal
and do so at a lower cost, more common alternator, and perhaps as good or better efficiency.

That looks like a nice solution, Bob; finding some suitable surplus transformers would make it sweet. 

12V sure is a bugger,  don't know why more folks aren't thinking 120VDC.  :)

there are a number of options for press in diodes and Todd will know what to use
they are much cheaper, fast recovery, and avalanche will be fine and actually desirable for your
application.

i have some i have used with success that are 200piv and 50amps each, they cost about 5 bucks each
you ought to be able to parallel up a set to get you where you want to be.

if i were to spec a stud mount i would go for at least 200piv, maybe 100amps, fast recovery and avalanche at 30volts
or so for your application, the avalanche will catch spikes presumably and protect you delicate electronics.

its going to take some explaning to Todd, as my bet is he has not had to deal with out of the box applications such as being
described here.

if he has concerns about the ability to make such a system work, ask him to look at a A001-4417jb leece neville
it uses 12volt excitation and produces 48 volt output, so it is proof of concept should the question arise.

bob g

your needing to stick with 12volts pretty much limits you to the neihoff, i think

given the distances involved,

how many amp/hrs is the bank again? i guess i need to go back and reread what your bank is comprised
of.

bear in mind that flooded lead acid batteries are at their peak charging efficiency being charged from 50-80% SOC
and then let the solar pick them up from there if possible.

your system requirements provide some interesting challenges that i haven't considered for a very long time, namely
the use of both a 12volt system and the troublesome long distances between the alternator and the battery.

depending on how big a hurry you are, i have one of the 4417jb's which i can use easily on my system to try out the transformer
pack and remote rectifier approach,  i also have a stack of transformers to pick from that would be nicely suited for the project.

if my back will allow me i will set it up for a trial run this weekend and see what the results are, this is an approach i have been wanting to try
out back when i was thinking of a 12volt system such as yours,

coming across the huge stack of 48volt exeltech inverters moved my focus up from 12 and 24, and am now committed to 48.

but i still want to know how this scheme would work out, and am willing to give it a go to find out.

at some point i am going to publish part 2 of this white paper, and it may as well include the transformer pack system.

reportedly the efficiency of such a system can be quite good, it would be interesting if it is in fact a reality to actually be able to
generate, transfer, stepdown and rectify and still show an improvement in efficiency,, most would be satisfied with a modest hit
in efficiency just to be able to cover the distance without using double 4/0 cables.

fun stuff huh?

let me know how Todd reacts to this scheme, i haven't had the pleasure of dealing with him much over the years, although i have
a couple of times, the last time when i was trying to find a balmar distributor in the seattle area, that was several years ago.

bob g

its not a matter of compensation, but rather one of time and a limited physical capability that seems to be
getting worse rather than better,

i started physical therapy last week, the result of which left me almost unable to walk, then did it again monday
and have not worked since!  damn that little PT although small and cute, is about to kill me!

i would be more than happy to help where i can, and have a few parts to use for testing if you need them.

the biggest issue i see with your proposed system is it is an out of the box problem and 99.9% of the alternator shop
guys go crazy when confronted with odd projects. those sorts of projects take more time, time being money, and bitching
from upper management.

if you have a good personal relationship with Todd, you have a huge leg up in my opinion.  keep in mind though that when
it gets too complicated he might lose patience with the project in a hurry, and understandably so.

you might offer him a bottle of his favorite solvent, or a coupon for a steak dinner for him and his wife, that might get you in
good and have his attention. i am thinking you are best to lay out the problem, the possible solutions, and ask his input somewhere
outside his normal place of business. somewhere that doesn't have a phone or some counter guy pestering him while he is trying to
get his head around your project.

none of this is rocket science, but it does take a bit of uninterrupted thought to grasp the concepts.

best to have it all laid out, so that he can see you have thought it through and have considered all the angles, and better
have explanations why standard approaches aren't appropriate for your application.

fwiw
bob g

the old handyman book while very interesting, thank god we have progressed to where we have
something better for rectification than that described in the book.

although every mcgyver type should probably have this at his disposal  :)

it is also interesting how in the early part of the last century diy'ers thought nothing of building and winding their
own transformers for whatever need was at hand.

everything from small lighting transformers to arc welders, they just jumped right in there and went for it.

filling the need was the order of the day, and efficiency was probably a distant second place, followed not so closely
with safety concerns.

this battery charger autotransformer is a classic example, no line isolation with an autotransformer.

doesn't look terribly safe to me, but if faced with no other means of charging a battery??? who knows???

desperate times call for desperate measures!

:)

not sure i would want something like that on board a boat with me!

bob g

a bit more thought on your project

another option that might be worth a look

perhaps a parallel set of delco bridge rectifiers, some of the large high capacity delco's
did just that to increase the capability of the alternator while using common off the shelf
rectifier bridges from their smaller alternators.

i would have to do some digging, but i am almost positive there are some high output delcos
that used either 2 if not 3 bridges in parallel operation.

they are cheap, readily available, and easy to work with, and have all the attributes needed
in that they have the fast recovery, avalanche and heat sink all in a prepackaged unit for 3 phase operation
at much higher frequency than you will be running at.

that would be a simple solution, to that problem

i mentioned the use of recycled final drive transformers from old ups units, such as the apc brand
the 1400xl is rated at 1440 kva, 1050 watts per unit, and my bet is the transformer is not the weak link.

i bet they can operate at the 1440kva all day long, the secondaries are conveniently wound on the outer section
of the core as needed for this application, and are very heavy gage rectangular copper. they should handle upwards
of 100amps each on the secondaries, connected in delta i think you might get your 250amps at 14.4volts charging.

probably be prudent to put the transformers and rectifiers in a fan cooled and vented enclosure, but i think you could
put together a test unit for very low cost.

the fan could be thermostatically controlled to keep down losses, or simply have it run only when the alternator is charging
would be easy to do.

hmmm, more to think about

bob g

Lloyd:

the CAT link is invaluable to this group on so many levels
would you mind starting another topic in the white paper section,

in the subject line put "pdf, CAT engineering file"

that way it can be located quickly

i have seen various subsections of that pdf, but never seen a comeplete work on the subject
there is tons of useful info in that pdf, some is dated, some is not directly applicable, but most is very useful
in my opinion and will provide answers to many questions that come up from time to time.

thanks for the link

bob g

I like that large, open heat sink rectifier bridge, looks like it has nice connections.    Got a link ?  8M 300a 600piv 6d


I don't like the 2nd one, with a link, and the cooling fan. Fan will suck in dirt and gunk, along with air, and they eventually fail.

if they can build it to take perhaps as much as 600hz, why not?

however i would include fans even if they say they don't need them, you might sail into the tropics
and be somewhere with very high temperatures?

because the fans will only be running when the alternators are charging, and presumably only when the
temps are high enough to kick them on, even cheap fans likely would outlast you and me together.

its not like they would be on 8 hours a day as with a solar controller, or 24/7 like an inverter

what are we talking a couple hours a day?

yes  i would include fans, and a screen filter such as used in industrial cabinets to keep the crap out
and to provide fire protection,  those metal mesh screen filters do both quite well.

failing that, be sure and mount the heat sinks in such a way that the heat flow is good, and there is nothing
above them that might be overheated by the additional heat, also figuring on extra heat from high ambient temps.

bob g

just be sure the rectifier supplier knows that you might be running upwards of 600hz
which will dictate the use of fast recovery diodes, rather than the standard variety that are good only to a bit
over a hundred hz.

the supplier will understand the need if you tell them what the supply is, if you don't they may assume this is a standard
3phase rectifier bridge for use at line frequency of 50 or 60 hz,, which 99% of there business is centered on.

not all rectifier manufactures make fast recovery diodes or rectifier bridges suitable for use at 400-600hz or so,
that will handle the amount of current you are going to ask of them.

bob g

well you don't have to use the transformers, but
the 3 phase cabling is still going to need to be quite large in order to keep losses down

what size? i don't know for sure, but i suspect it might be as large as 3 x  1/0 cables to get basically 12volts ac
from the alternator stator, some 30 ft? to your rectifier bridge.

the toroids allow the alternator to run at a much higher voltage, higher voltage allows you to transmit the same power
but at proportionally lower amperage.

amperage is what dictates the required cable size

before you order the toroid transformers you will need to know just how high a stator voltage can be at perhaps 50% field
excitation at the speed you want the alternator to turn (4500rpm?)  i mention 50% because it provides some room to wiggle
when it comes to maintaining voltage under load.

if at 4500rpm and 50% excitation current the stator can deliver ~60vac, then we might want to look for a transformer
that can step down the 60vac 3phase and deliver it to the rectifier so that the result is ~14 vdc.

thinking about it, i might want to start out with 25% excitation and work back from there, that way i have lots of room to
increase the field and the output of the system.

that is why i would rather work with cheap surplus transformers and prove out the concept before i picked an expensive set
of toroid transformers.

unless of course you are not locked into a fixed 4500rpm, if you have some flexibility there , then your options increase dramatically.

bob g

Lloyd:

bear in mind that the published curves for the neihoff will be vastly different than the curve of the alternator
as applied here with the transformer pack.

in other words the published curves only give you an indication of what rpm might be needed to get to the output
needed to feed the transformers.

bob g

Lloyd:

after going back and taking another look at things, particularly the power curves

it appears that as built the alternator will not make 60volts at any decent amperage unless it
is turning balls out 8krpm

so, unless the stator can be reconnected as Y instead of delta, there is likely no way to get that
much voltage out of it.

i haven't worked with that alternator so i cannot comment on whether or not the stator can be reconnected
as described.

if you can, then the voltage goes to 1.73 x whatever voltage it can make now at something like 6krpm, which i would suggest
is probably a more realistic goal. 

at 6krpm the alternator should make ~36 volts nominal at maybe 150amps, and reconnected then we would expect
36 x 1.73 =62.8 volts which is about where we need to be in my opinion

at 5:1 we only need about 50amps from the alternator, which is no problem and will require smaller wire to transfer the power.

feeding this into a 5:1 step down transformer returns us to 12volt nominal at 5 x the amperage or 250amps.

so from this it appears that a good starting point for testing might be 6krpm alternator speed, and a reconnection of the stator
from delta to Y (wye, star).

i have no idea whether the neihoff alternator stators can be modified and reconnected as described, and i doubt Todd is going to want
to do the modification.

bottom line?  don't buy an alternator yet, and don't buy any transformers yet
if you are set on the neihoff alternator you might be stuck running triple 1/0 cables from the stator connections to the remote rectifier bridge.

personally i don't like it, but it may be what you end up having to do?

i think it might be easier to accomplish using a leece neville alternator, because of having a single stator that is a bit more agreeable to modification.

remember if it was easy, everyone would be doing it

bob g

An alternate possibility-  If a schematic for the Neville regulator can be had, it may be practical to modify the regulator for a remote voltage sense.  I can look at it for you if you can get the schematic.

Alternately, see if Neville engineering will make this modification. This is not as good a solution as the transformer setup Bob suggests, but it would allow for as much voltage drop in the wire to the battery bank as you can stand, efficiency wise, which in turn allows for a smaller pair of wires.  


It drives me nuts to see alternators of such low voltage and high currents without a remote voltage sense capability!

Bruce:

he has the balmar mc612 controllers now, they have the remote sense wire which would
be very good at adjusting to overcome cable drops as you mention.

some of the delco and leece neville regulators also have remove sense capability, altering those
that don't would pretty much require destroying the units, as they are impregnated or potted
pretty tightly.

its just really difficult to armchair design around and unfamiliar alternator like the neihoff
nothing wrong with the alternator, i just don't know for sure how it reacts to different operating parameters.

at least not enough so to feel comfortable in spec'ing expensive transformers.

having said all that, i am very interested in Lloyd's project, it would be a serious application of the principle
and addresses most if not all of the concerns related to 12volt systems and long distance transfer of large amounts
of power. (relatively speaking of course)

he gets this sorted out and working well, i suspect there will be much interest from a certain sector of offgrid folks that
are using 12volt systems.

it wasn't long ago that i too was planning a 12volt system, the difference would have been the transmission distance
would have been under 6ft, i figured 2/0 cable was sufficient for my needs at that distance and ~150amps.

once you get invested in a certain voltage it is hard to make the jump to another, thats for sure.

bob g

Bob, now I understand why you like the Balmer controllers.  For 12V systems, remote voltage sense is a near necessity.

 

Are the Zena alternators crappy?  The seem to have some higher voltage options, and claim to be continuous duty types.

http://www.zena.net/htdocs/alternators/alt_inf.shtml

Lloyd:

no worries here, you aren't wearing me out at all.

the 12volt and 30 ft situation is just something i haven't given any thought to, actually like i said
even when i was seriously considering 12volts it was with the idea of keeping the distances down to inches if i could.

i wanna do some testing on my end, collect some data, and crunch some numbers.







Bruce:

i haven't looked into the zena alternators for a few years, it looks like they have expanded their offerings.

i don't have a clue how good they are, or aren't

bob g

i have been following perraults work for many years, and figure to make a trek to meet the gent at some point in
the future.

while i agree on most of his assessments i part company with him on the predominate loss factors of the lundell design
at least as it applies to the 110-555jho and the 4400 series leece neville where it is clearly the I2R losses that are the prevalent
limiting factor.

there is a ton of reading out there if one digs around a bit, some of it very good.

it amazes me how few people that work with automotive alternators are unaware of the work that has been done recently, or rather
the last decade or so.

bob g

all of the 24volt machines i know of also use 24volt fields and excitation

there are only a couple or so 48 volt machines i am aware of that have 12volt excitation, and i only verified this after i wrote the
white paper at the head of this topic.

i am in hope of getting in to see my dr this week, and get him to adjust my pain meds so that i am feeling able to get back into the shop
and do some testing and maybe get some useful info to you that might help you with your system.

the last 7 months with my current dr. has been horrible, and i thought it was due to my declining condition, i found out yesterday after meeting
with my pharmacist that this dr has me on 50-60% of the daily load than that of my prior doctor that had my pain under control for the 2 plus years prior. (even at the higher load, i was under 50% of max doseage).

that was a huge eye opener for me, i had come to believe that i was going down hill fast, and might never be able to work on completing my projects or even do more testing.

fingers crossed here, hope to know later this week whether he is willing to increase the doseage to the prior amount.

i am beginning to understand why there is a black market for drugs! 

you know things are getting bad when you can't even work two half days a week, and have tears well up in  your eyes just to get up
to go the the bathroom.

bob g

Bob, thanks for all the work and effort and even more so for sharing.

I hate to hear about your health and the effect it has on your work.  I do hope that your Dr. can find something that works well for you.

Look forward to hearing more from you on a very interesting topic.

Kevin

hey now, don't get carried away there, i am a mere mortal diy'er like the rest of the membership.

(although professor bob has an odd ring to it, don't you think?)  :)

i am not at all familiar with the unit you have in your diagram, or how it would be best used to accomplish
what you are after.

having gotten my dr. to up my meds i think i am going to be up to doing some testing this weekend (sunday)

i am also pretty sure i have everything i need to do the test that you need, for higher voltage generation/transmisson
then a 3phase transformer step down, rectification and charging a 12volt battery.

this is really not something i plan to use myself, but i have no problem setting up and giving it s whirl to see if it works
out to be something you might find useful.

bob g

well i picked out a nice matched trio of 1kva transformers, the secondaries are heavily wound with what appears
to be ~3/32" x 1/4" copper, and probably about a 5:1 ratio

i attached a junction to the primaries and connected them as delta, and used a 3 wire 10guage piece of nice stranded rubber covered cord.

the secondaries are connect in Y configuration, because the alternator i am going to drive it with puts out about 60volt under load
and a 5:1 step down would get me to 12, but i opted to go for the 1.73 step up afforded by Y connections for the first test.
that should allow me to get solidly into the 14 volt range after rectification with very low excitation current, after the initial test i might
reconnect the secondaries as delta just to see how it works out.

for a rectifier bridge i cheated and used an oem set from an old leece neville i had laying around, i will have to put a fan over them if i try
to pull max amps for any length of time.

i have to attach a 12 volt battery for it to work against and a dummy load, amp shunt and attach the other end of the 3 phase cord to the stator
external taps on the test alternator. and of course the controller to provide excitation and monitor the sense line to the battery.

the test should prove the concept in that the alternator will be excited with a 12vdc source, and managed by the controller, via the sense wire to the battery

the alternator will provide ~60 volts AC 3phase, which i will take off and transfer a few feet with my 10/3 cord

the transformer will do the step down to a voltage low enough so that it can be rectified and provide for charging at around
14.4vdc

i will be running two tests, one with the alternator in stock setup, and do a bsfc at a fixed load of X amps at 14.4vdc
and then run a second test with the alternator running with the remote transformer/rectifier setup, a the same X amps at 14.4 vdc

from that i should be able to tell if/or there is an increase, decrease or parity in charging efficiency of the system from that of the stock oem
alternator.

i would expect some losses, but there might not be as much as i would expect, and there is some supporting text that would tell me
that the system will return a higher efficiency over the stock oem alternator, even though there are transformers involved.

sunday is the next opportunity to run the test, and i am looking forward to getting some decent testing and solid data for discussion here.

btw, this topic has morphed well away from the original intent of the white paper section of our forum
next opportunity i get i will split out this new direction and setup another topic under "testing" or somesuch, and after we get some solid
results and a workable system we can then writeup another white paper to cover this method.

gotta think how best to deal with all that later, for now i just want to get my head around a full battery of tests and setting up a protocol
to get as accurate data as possible.

more to come

bob g

decided to move the experimental portion of this discussion over to a more appropriate board

http://www.microcogen.info/index.php?topic=687.msg8141#new

bob g

Bob  I just found your paper on alternators. Excellent  read BTW.    Interestingly I arrived at  choosing the same 160 amp Prestolite alternator by a totally different route using completely different criteria. In my marine design work I deal in a very small niche market of boat owners who cruise long distance , some of them literally around the world.
While I worked for Xantrex as a a marine applications / sales engineer I met  a number of interesting people  including the staff from Balmar.  Since you used a Balmar regulator  I assume you also know pf their other product offerings.
My  clientele  wants  a totally reliable charging  system and if they do need repairs,  want to be able to find competent service people any place in the world. They also would want  readily available parts  and not have to have them sent air mail from back home.
Given the electrical demand  found on a typical  modern yacht  a 24V system is preferred over a 12V system.  As you clearly stated  in the paper concerning I squared R losses, the higher voltage  at same wattage means less current. The cost difference between wiring with  2/0 instead of 4/0 is very compelling.  ;D
I always specify Balmar  regulators because of the Amp Manager and specify the regulator be limited to around 95% - 90% or less of full output since this also serves  as a added protection feature. 
Many of my systems  require the use of twin 160 amp alternators driven b y the same engine pulleys.   Average loading  would require close to 200 amps @ 24V  and peak demands hit 400 amps.
My clients  do not like to listen to a diesel genset rumbling away  overnight so they want silent power from inverters  but  when cruising in the tropics  they still want  air conditioning  overnight. 
Because you cannot store AC power  this requirement leads to needing batteries  for storage of DC; and  24V is the most common system voltage. 
Yes I know 48V makes more sense but in the marine world a lot of regulation mandated safety equipment navigation gear etc. is only made for 12V, 24V DC, or  230V AC ( european) so the vessel system becomes 24V DC  and either 120V or 230V AC. 
To provide  AC power I rely on Victron  equipment which is a European  company with  manufacturing in India not China so the quality is better  than chinese built equipment.
Design wise the Victron outperforms  products like Outback  in some key  areas. For examble  their chargers can handle  either 50Hz or 60HZ and the latest  models of their Skylla charger  handle any voltage from 90V to around 265V AC over a wide range of  frequency and it will even handle  several hundreds volts DC.  This one feature alone makes it an  almost  perfect  candidate for  running from near unregulated AC generators. Their sine wave output inverters run at about 95% efficiency. The  inverters  can be  synched  in parallel to deliver  15 - 20 kW of regulated stable  AC power provided the DC source  is capable of such high currents.
Dr. Jim Clarkes 'Hyperion' yacht  had  around 45 kW of 3 phase inverter power for silent night running.  BTW  the Victron can also be configured for 3 phase power.


Now that the old Prestolite VLF series 300 A @ 24V alternators are discontinued  the next  best choice is the 160A  Prestolite model.  Balmar deliberately designed their MC612 or MC624  regulators  to handle 10A of field current  so it is possible to govern two alternators  from one single  unit.  It makes for a more stable  output than  when driving two separately  regulated  alternators feeding the same battery.  So a pair of these 160 Amp alternators paired up and derated to 150 amp output still provided 300 amps of output current.
Unfortunately  my photos of  such installations are too large to post on this forum. 
Elnav

i have been following victron for some time now, particularly their work in testing various classes and manufactures
of gensets in the classes we work with.  it is nice to have a goal post to work toward and they have provided that
with their published test results.

for me, i started my quest for learning based on my belief that it might make more sense to charge batteries and then
use the power through inverters using a genset, that was about 12 years ago now.

in the beginning there really wasn't much published about this principle for offgrid use, and quite frankly the whole sector
has been slow to adopt the strategy, so

i spent all my time researching two major sectors to adopt the technologies and develop my philosophy, those being
both "NASA" and "Marine" and of course pawing through tons of paper from sandia labs

it didn't take long to find overwhelming support for the strategy from both sources, mainly in my opinion because they
are both the ultimate in off grid, you can't plug into a grid in space, nor can you out in the middle of the pacific.

the limited run time at peak load, charging a good set of batteries and powering a good inverter has far more "pro's" than
"con's" in my opinion, efficiency, increased lifespan, improved heat quality, lower emissions to name a few of the positives,
first cost and complexity might be said to be the "con's"

as far as i am concerned offgrid folks could learn a lot from the marine side of things

as for balmar and the mc612 being fuse limited to 10amps, yes they can control 2 heavy alternators in tandem, and the fuse can be
removed and replaced with a 15amp as per balmar engineering (but i might not want to do that myself)
otherwise the unit has so many useful features it is hard to imagine building an engine drive dc charger that isn't controlled with a balmar
or comparable controller. that amp manager is of huge benefit for trigeneration where a refer compressor is also driven by a smaller engine
and one is faced with trying to share the available power between the two driven components

the only thing i don't care for with the balmar is its being potted and non repairable should something go awry, they are fairly expensive
and it leaves a huge pit in ones stomach to see the smoke come out of one and know they are not repairable.

bob g