I've tried, but I just can't kill it.

[glort]

Following a discussion a while back about using a regular car alternator to charge Batteries where the opinion of some was they wouldn't last, I decided to put it to the test.

I grabbed a couple of small frame, internal fan 80A Mitsubishi alternators and hooked one up to one of my Vertical Chinese Diesel Engines.
Using a couple of car battery cables, I hooked the alt to a car battery with a multimeter to monitor Voltage. I then used 3, 12 to 240V Inverters and a pile of 12 Headlight globes and Radiator cooling fans for a load. I don't know what the load actually was in watts, I just kept piling them on till the battery voltage went below 12 V and then I knew I was well over the alts capacity.

The alt was driven at around 5000 RPM. I have this engine a bit throttled back on the governor so I estimate it's doing about 3500 RPM and as it worked out, the serpentine pulley I had on the engine was exactly twice the size of that on the alt.  I had a bigger pulley off the original Subaru engine everything came from but it was  a neat 1" where as the shaft on the diesel is only 3/4 so I took the pulley off the Power steer pump and bored that from 1/2" to suit. I manually sped the alt up ( a lot) with the alt at full (Over) load and it didn't make any difference to the voltage at all meaning it was maxed out electrically and extra speed wasn't going to help.

I have done a few runs with the alt overloaded as evidenced by the battery staying under 12V Which took a bit of tuning to not let it discharge too quick at which point the inverters trip out on their low voltage setting.  All Up I have done around 8.5 hours so far.

While the alt gets hot and gets hot fast, I notice at the back of the alt where the electronics are, the temp there is markedly cooler than towards the front  where the windings are. On this alt I can put my fingers on the rectifier and it takes a while to discern any real heat from the thing. The front of the casing is a different matter and that gets too hot to hold ones hand on for more than a few sec. That said, That still pretty cool because my pain threshold with heat is low at about 60oC so it's still pretty cool really.  I have opened the bonnet of my car plenty of times in summer and couldn't put my hand on anything in there.

There is an impressive amount of air that comes out of this alt as well as quite a bit of heat. I reckon they would make a great fan heater if you  could capture it!
I connected the 2 wires that come out of the alt together. I'm not sure what was what. One seemed to collapse the field when put to positive and the other one seemed to allow the voltage to go well over 15V which was the same if neither were put to positive. With both wires joined and put to the positive side of the batt the alternator held 14.58 volts very steadily and was still above 14V with 800+w Load.

With the batter voltage under 12V even for 3+ hours, as soon as I took the overload off, the battery voltage with the alt going came up in about 30 sec and leveled out at 14.5+V One thing I did was to have a load of about 800W on the alt and take it off the battery so the alt was running the load direct. I did this for about an hour and 5 min and the alt wasn't that hot nor did it suffer any ill effects.

While this is a very short test compared to what off gridders may put on a machine to charge their batteries, I can't see any reason these things would fail charging a battery bank or providing power.  They certainly don't seem efficient, I was surprised at the amount of fuel the little engine went through and I have just cleaned the pump and injector and tested both before the test as I hadn't used the engine in a while.

I'm sure over all a modded alt like the ones Bob does with the outside controllers would be far better for an everyday solution particularly from an efficiency POV  but for a cheap, simple, high output and occasional use solution, I have every reason to believe these alts would not burn out if over loaded and would give many hours of trouble free service in a battery bank charging application.

[SteveU.]

Good report glort
Matches my expereinces. You'all think about it. An external front fan only "conventional" alternator must pull ALL air flow through the narrow as can be made rotating rotor and stationary stator air gap. AND do this when the rotor is spinning flinging off sucked in between the claw pole gaps air all being swirled and stired up. Chrysler engineering realized this back in the early 60's and why they came up with the much more sensible internal dual fan design to be able to have TWO double unresticted doughnut air flows to work WITH the dynamics that were actually going on. Not singing praises for their execution on this design. But thiers like all of the other automotive alternators back then only had to prove higher output over a wide useable RPM range and longer life versus the previous used all output current flowing the brushes generators. Ha! And then penny pinched down to do this cheaper, and lighter, with a higher profit margin. Why the stupid,  hated  press on pulleys and spring clip bearing retainers! Point is the design goals back then by small case designers was NOT to do this for optimally highest output, or the most conversion efficient results.
You can see the evidence of the known poor single pull through fan air cooling in the flats on the Motorola small case and others on the stator outer lam stacks and the later 12 and 15SI Delcos with the case D notches to at least allow hopefully for some additional rotor flung out perimeter  air flow cooling. Another way tried to improve cooling was to machine tight fit the stator lam stack metal to metal contact with the alumunum end cases and let the aluminum hopefully transfer away the heats.
ALL of these ideas except for the dual internal fan failed once underhood temperatures got jacked up with emmisions comtrols, vehicle downsizing, and crammed packed under hoods with decreased underhood air flows due to extrenal streamlining. And all along the increasing continual demands for contious vehicle elecrrical power demands. By the late 80's contious 70-90 amps power needed contiously was now a common demand. Not just a luxury car demand met with special  larger cases alternators.
So small case units HAD to upgrade to do this. Millions and billions of hours and 25 YEARS NOW now doing this in summer time heat in traffic jams, desert runs and grade puliing with these different brands of double internal fan units.
Stand-alone only having to to cool themselves at thier hot rated output is a peice of cake compared to average underhood conditions theses have had to work in over the last 25 years.

To have these availble as scrapped/idled/parked vehicle take off's for pennys on the dollar is one of the best DYI values out there.
Any effiencicy nut willing to spend 10X that for an Oohh-Woo permanet magnet 10-12SI conversion unit has been drinking too much of the coolaide or time warp stuck back in the "good old days of the 60's and 70's". Man That was 40-50 years ago. Just dump out of the Internet, PC's digetal cameras and cell phones while you are at it, eh?

You betcha there are many more absolute efficient units out there for 20X to 100X the price of these double fan auto's as used take off's.
Heck. I'm with Stalin on this one. "Quanity becomes a Quality after certain point".  These proven internal fan units are out there available and cheap, cheap. Cheap enough to have 1-2-3 working with the same as spares and still be money ahead.
Ha! Probably as a woodgas fueler with waste heat as ain't a waste but more of a needed fuel conditioner resource is biasing my thinking now.

Glort you know of course you can up your engine fuel effinecy by downing your engine RPM to a loaded 2500+/- RPM (watch the oil temperature) and downing the alt RPM to the lower end of the actually needed RPM for output and cooling. 'Aught to be good for a min 25% to as high as 50% fuel use reduction with some fine tuning. THATS how the home woodgas systems I'm involved with get set up for the very best sows purses systems. Leave the alligator designer clutches for the well heeled and fashion concious intelligentsia's.
The raw wood fuel may be cheap. The fuel prepping labor is not.

Regards
Steve Unruh

[mobile_bob]

hey guys i am all about saving a buck where saving a buck is in keeping with reality and the goals set forth.

for a backup generator/charger why not use what is commonly available for cheap?  that seems reasonable to me as i suspect it would for most folks.

where i part company is with the dual fan thing...

having to add another fan, to remove heat should be a read flag in my book.  we ought to be asking why is there so much heat to remove in the first place?  we all know the answer to this of course, that is it is far cheaper to build a high output alternator with poor efficiency and add an additional 10 cent fan than it is to design and manufacture an alternator that can put out similar outputs with enough efficiency not to need the extra fan in the first place.  it is also pretty cheap to design and integrate a plastic duct to bring cool air from outside the engine compartment and route it through the rear of the alternator case to cool the rectifiers/regulator and the stator, however... ducts take up space, which is at a premium these days, so dual fans are the norm as is spinning the living sh$t out of the little bugger in order to get the needed output and ample hot air flow to keep the thing from dripping on the ground.

thankfully there is no reason for a diy'er to have to deal with these 200+ degree F underhood temperatures.

for my testing and long term goals is the development of an alternator that can be used out of the box (or as nearly so as is possible) and have it be able to do 48vdc nominal charging (capable of sustained 57.6vdc operation) without the need for additional cooling (meaning only the use of the external single fan) "and" do all this while returning efficiency over 70%.

now i have found such an alternator that will do all this for 24vdc nominal operation, and return excellent efficiency with the 110-555jho as described in the white paper, however it "may" or "may not" prove to be as successful doing the 48vdc nominal duty, at least not without a bit more modification, added parts and complexity.

in a 12 volt DC world we have literally dozens if not hundreds of options, in a 24volt world we have far fewer and in a 48vdc world the options are quite narrow and equally dear in price.

what i would find interesting (even though i have no desire to explore the option) would be to fully test one of these dual fan small case alternators at its native 12vdc operation and quantify it in BSFC then repurpose it to 24vdc operation and see if we could get more effective watts output with less heating?  it think it might be possible with some of these to increase their efficiency significantly, however i would not suggest using one with a wye connected stator, and stay with star connected stators.

if i were a single man at this point in my life, i would opt for a very small cabin and lifestyle, and i would live with a 12vdc battery/inverter system, and i would surely be taking a fresh and hard look at these newer dual fan alternators "if" i had a reliable source for them.  problem being i am married, live in town even if in a modest house 12vdc is out, and i have "no" source for used alternators of any sort... be they small frame, large frame or whatever!  around here there just isn't any good source of parts like i had for years living in the tacoma/seattle area.

even finding something as simple as a hose clamp or a bolt can mean an hours drive and 20bucks in gas.

anyway i digress (as usual)

i think Glort makes a good point,  why not use one or more of these small case dual fan alternators? especially if it is planned for a backup system?  that much makes sense to me.

bob g

[glort]

where i part company is with the dual fan thing...

having to add another fan, to remove heat should be a read flag in my book.  we ought to be asking why is there so much heat to remove in the first place?  we all know the answer to this of course, that is it is far cheaper to build a high output alternator with poor efficiency and add an additional 10 cent fan than it is to design and manufacture an alternator that can put out similar outputs with enough efficiency not to need the extra fan in the first place.  it is also pretty cheap to design and integrate a plastic duct to bring cool air from outside the engine compartment and route it through the rear of the alternator case to cool the rectifiers/regulator and the stator, however... ducts take up space, which is at a premium these days, so dual fans are the norm as is spinning the living sh$t out of the little bugger in order to get the needed output and ample hot air flow to keep the thing from dripping on the ground.

thankfully there is no reason for a diy'er to have to deal with these 200+ degree F underhood temperatures.

And that to my Guess bob is the thing with the Dual Fans more than INefficiency.

Cars even 30 years ago had relatively open areas under the hood and good airflow to boot.  As a young guy, A car only came into my drive way as stock and when it left after arriving for the first time 99% of them were modified to increase performance. As anyone knows, more performance ,more heat but NONE of them ever had the under bonnet temps that every new car I come across now has.

Of course the thing these days is fuel efficiency, cost saving in production and packing in as many features as possible.
I think the Under Bonnet heat the alts have to cope with and the fact nearly all alts are delivering 3 or more times the power they were 30 years ago would have BIG influence on the cooling above the things inefficiency.
 
I know the Alts from one series of Subarus that are Exactly the same as the ones I have been playing with have an extra wire that allows the vehicle COMPUTER to control the charge in order to maximise fuel efficiency.
As I understand what I have been told, they worked a bit like a regenerative braking system. The computer through the Throttle position sensor knew how loaded the engine was and also vehicle speed and had a Hysteresis where it would kick the alt into high charge when the car was say running down a hill or braking after letting the charge go a bit lower than it would normally.  Under load, the alt would be kicked out unless the voltage fell below the min threshold value.

Supposedly, this was supposed to save 5% of fuel over the life of the vehicle ( whatever the hell that means which I surmise isn't what one would assume. )

I think if you were paying for fuel to run the alts frequently it would be stupid not to set up an alt like your pet favourites, however, if they were only to be used infrequently, then the fuel saving may not justify the extra cost over the cheap and cheerfuls. 

It would be interesting to see what the newer twin fans could do if externally controlled.

[SteveU.]

Ha! Ha! Got you both on the ASS-SUPM-TION that dual fans will take more parasitic power than a single fan!

First though lets all just agree that as you Home DYI step up in your voltage system base from 12 VDC to 24VDC to 48VDC that the ease of getting generating and therefore fuelshaft effiency become much, much easier. No disputing that. But as you have conceeed MB then other equipment costs then multilpy by quantum factors.
Same factors in the commercial power distribution with thier voltages and frequencies.
So lets just stick with 12VDC generating OK?

The dual internal fan alternators use smaller individual fans moving air against less resistance; and moving air in a more dynamic logical fashion. They take less shaft wattege to oprate than a comparable sized/output/effienccy designed single external fan cooled unit.
This was true of the old Chrysler auto units. This is true of the modern units.
I've done an awful lot of smoke air flow testing to discover this. A LOT of no fan/enlosed unit testing for heat gentating and dissipation runs into thermal destruction.
First heat building is the diodes. Next the stator windings and core. Rotor heating in comparision is small. With bearing heat the least contributor.

Here are the unaviodable working air and heats flows dydamics.
The claw pole rotor WILL always be spinning fling air from the center outward with much outer edge churning turbulence from the claw pole gaps, edges and tips.
An expernal single fan also expells air out of it's outer edge. THIS creates a center low pressure area at the fan shaft center area with air rushing into trying to fill.
In the external front fan front drive side these flows are bucking each other fighting for the same center repacement air. Of course with external shaft power and a larger fan you can force flow win over the rotor. The Hottest stator core/windings/rotor pole heats then get pulled down inward right past the front bearing housing before being expelled back up and out at the outer fan edge. The bearings naturally on thier own gnerate little actual heat on thier own and want to run OK with no fan. Unless that is until externally cooked by a slipping belt heats or overheated units heats being dragged past them.
A rotor mounted smaller fan on this side organizes the normally unorganized turbulant rotor air flow from inward to outwards. Coolest air is externally drawn in past the front drive bearing and expelled now heat loaded out the unit periphery assiting what the spinning rotor wants to set up anyway.
Now go to the electronic packaged rear of the unit. Smaller rotor mounted fan now sets up assiting this same inward to outer doughnut shaped air flow. Again bearing gets the coolest air first. Then the electronics package. And finnally out and past the hot stator windings. NO mechanical shaft wattage is used tring to drag air through the narrow extermly turbulant rotor to stator gap. Rotor is cooled by it's attached fans.
A single front fan unit MUST be fan oversized to pull air therough this gap to be able to try and cool the heat sensitive unit ass end and rotor cool. Really bigger hammer forcing flow. More cooling back there from the heated front fan air blowing past the unit outer cases and letting the rear rotor stirred air out.
Other Auto unit designers then Chrysler started realizing this in the early 80's. Why the GM plastic vacumn fans. Why the vertual cases skelentonizing especially in the rear of the GM and Ford auto units then. Why the extreme case notching at the stator edges then. Ha! I did this on my custom  units and dropped temepratures by 10F. To let the heated air out easier then dragging it through that rotor/stator gap. Ha! Chrysler just switched to the new Nippondneso dual internal fan units. Same as all of the Japaneses Auto manufacturers adapted. Later Bosch. Later Ford production. GM arrogance was the last with this. There were a few "CS" transion units with an internal rear rotor fan and the front of unit external vacumn fan.

Second assumption made - that these later dual internal fan unit were not effiency conversion upgraded also.
I DID test late 80's/early 90's units at 60 amps output.  Old style 10SI/12SI/Motorcraft piggy backed versus the "new" then "grapefruit"sized 60 amp Japanese units. Better output curve at lower RPM with less heat produced.
Then tested 105 amp Lestek 10DN based Designer units against now melon sized Japanese dual internal fan 100 amp units. Same much better low RPM output with less heat at all RPMs.

The USofA auto manufactures were, and still are fighting CAFE (Coprperate Average Fuel Ecomomy) back then and still now. THEIR engineeers have their  feet to the fires and were only then passing on into new production componets that could prove they WERE more individually power consuming efficiect. Thier jobs literally depended on this year to year.

Yes glort by the late 90's computor intergration of all accessories was then used for overall vehicle fuel effinecy crafting. Then direct computor controlling and overunnig drive clutches are used.
Nothing KISS anymore except your pocket book.

M.Bob not saying your crafting isn't worthy and worth emulating for the long term Doers.
Just folks in Africa, SE Asia and even outer reaches of the Americas quite often do have plenty of dead abandoned lay-a-bout vehicles from the past 25 years now  kicking around with these very long brushed, long lived units in them. Ebay/Paypal for new Chinese production are just not in their slim pocketbook options range.
Fooling with working trucks can get you shot. Abandoned Yuppie and NGO rigs are always fair game. My little 1500 person town I could walk end to end with five twentys and come home with five dual fan alternators off of deadlined minivans and such. Ha! Pitch the GM "CS's" and the 80's Ford piggy backs with the plug in outputs into the scrap!

Regards
Steve Unruh

[mobile_bob]

not sure you got me on any "assumptions" Steve!

nowhere that i recall have i written any verbiage about dual fans using more power than a single fan... if you can show me otherwise i will stand corrected.

because of the "square" law of air flows, when you double the diameter of a fan you quadruple the power it takes to turn it, i would expect a larger in diameter external fan would consume more power than twin smaller internal fans.

my point is this and this only... anytime i see a design calling for additional cooling, i look to explanations as to why?

yes underhood temps are rising, and things are packed in tighter.
and yes todays alternators are asked to provide 2-3times the power they were asked to provide 40 years ago, and
yes they still seem to be constrained to keeping the same small frame size or nearly so.

all of these things work in concert to make for a very difficult to provide for solution, and most of them also work to destroy efficiency.. lower efficiency also makes more heat, sort of a death spiral so to speak.

yes they have gotten around some of the issues with lower efficiency by giving computer control over the alternator, disengage when we need power to pass, engage when we go down hills, and any number of other parameters are or can be tightly controlled... the end effect is to try and regain some of the losses that have been mounting in these small frame alternators because we seem to be stuck on the 12volt standard.

when the day finally comes that the oem's step away from the 12volt standard and up to 42vdc or whatever their hearts desire at that moment, then we will see higher efficiencies and far less self generated heat to have to pump out with dual fan's.

finally as i have said, and i will repeat it again...  if i had a good stable supply of useable small frame alternators at an affordable price... then hell yes i would be working with them, however

this is not the case around here,  i have to go to ebay to find alternators or buy new/rebuilt units with core charge included (if bought locally), so...  given that choice you won't find me working with trying to improve small frame alternators for use in 24 or 48volt systems, not when i know that i can pickup 110-555jho alternators brand new, in the box, no core charge for about a buck an amp pretty much all day long.  i can't buy used alternators around here, at least not more than maybe one every 6 months when one pops up for anywhere near 30 bucks... the only yard around here seems to think that his used alternators are worth a C note and i have to pull the damn things off too!  why would i or anyone do such a thing when an additional 60 bucks will buy me a brand new 555 that will kick any of these dual fan small case alternators ass seven ways from sunday?

i sure miss the local "pick a part" in south tacoma!  there i could pickup small case alternators for 15bucks each iirc and maybe another 5 bucks for  a core charge?

lastly...

i have beaten the drum for the 110-555jho for over a decade now, worked with it extensively, and had others follow my lead with huge success, maybe someone can step up and do the same work on one of the dual fan small frame alternators and provide some solid test data to support their use and as a result provide another option for folks?

that job is open for anyone wanting to step up and do it!



now as for sticking with 12vdc?  ok we can do that as an academic exercise i suppose, but in the real world if we are charging batteries we are going to be using inverters, and there really is no effort being expended in the 12volt market these days... at least not so much in pure sine wave and not in sizes large enough to reliably start well pumps without shutting out every other load.

don't get me wrong here, in a simple world i would be all over simple 12volt systems, it just isn't the reality for the vast majority of folks these days.  so in my opinion we must be working with at least 24volts if not 48volt generation.

bob g

[glort]

Ha! Ha! Got you both on the ASS-SUPM-TION that dual fans will take more parasitic power than a single fan!

Actually, I never even thought of the dual fans, I was thinking more of the construction and way the things are built. Having pulled a few of the single and dual fan alts apart, they -appear- to me to be quite different in the windings for a start. the single fans of similar amperage I have looked at seem to have more turns of finer wire in the stators whereas the duals seem to have much heavier gauge wire but less of it. Now this may just be to do with the specific Alts I have looked at but it was what I was wondering about over the fans.

One thing I did wonder about giving the new style better efficiency was how cool the electronics seem to run comparatively.  Sure the dual fans appear to put ut more heat than the singles in my observations but I certainly don't know enough to understand what sort of an indication that is. I do know that unless it's a heater you have, cool electrics/ electronics are a Real good thing.

As for the fans, they are a totally different thing to the external design. smaller, more blades, different shape. Even having mentioned it, I wouldn't assume they were more parasitic at all. They look a lot more effective to me but I don't know enough about fans to even guess at which one would require more power to spin at a given RPM. I have no doubts from observation which one pulls a heck of a lot more air though and as you say, from where you want it.

The other thing that struck me is being a straight blade, they would appear to work effectively either direction unlike the external  fans. Come to think of it I'm running them same direction as the lister and opposite direction on the china diesel. They both seem to run about the same temps from feel to my hand.
Got to buy some test equipment to measure these things!


Bob,
I read in several magazines must have been 10 years ago that auto manufacturers were going to 42V systems but I have yet to hear let alone see any vehicles using this standard as yet. Do you know what happened to it or why it hasn't been ( widely) adopted?

It seems our ability to source alternators is directly opposite. You can get the big ones cheap and I can get the little ones. The big ones here for me are a fortune. Since reading your recommendations I had a look on evil bay then seeing next to nothing and going for a fortune, I rang some truck wreckers. Bigger shock there!
OTOH, I was at my fathers wrecking yard the last few days and when I asked If he had any alternator Pulleys, he pointed me to a few alts. I said I only wanted the pulleys and he said just take them off those, they are going to scrap. I said aren't they good alts? He said yeah, but having 50 in stock is more than enough especially when I can't remember the last time I sold one.

If you want any small alts Bob and are prepared to pay postage, I'll send you a dozen mate! 

As for testing efficiency, how would one go about that?
I was wondering about coupling an alt directly by means of a coupler to an electric motor. I could then measure the watts consumed by the motor from the mains and the watts generated  by the alt with whatever load I put on it. I assume I would first have to measure the no load consumption on the mains engine and subtract that from whatever the final figure was over the time tested.

I know enough to realise there is a lot of hidden factors to this sort of test, perhaps you could point me in the right direction of doing a test like this as simply as possible but with meaningful accuracy.


one thing I was wondering the other day....
Is it possible to charge 2x 12V batteries with 2x12V alternators when the batteries are also wired in series  to supply a 24V load?
I was wondering if it were possible to use Diodes out of an alternator to prevent the effective short circuiting this wiring setup would cause?
I don't believe it would be possible to use self reged alts in parallel as the regs would sense a high voltage and the alt would produce nothing. Obviously with an external controller it wouldn't be a problem.

Is there any way to be supplying power from 2x12V alts  while a 24V load is connected at the same time?

[mobile_bob]

Glort

lets get into the weeds a bit, and maybe we both come away with a bit more understanding of both types of units.

yes you can charge two 12volt batteries with two separate 12volt alternators and then series connect both batteries to drive a 24volt load... the only thing to be careful of is isolating the grounds so that a series connection can be made without making a dead short on the second alternator and battery.

yes you can control two alternators with a single regulator provided you can get access to the brushes "and" the regulator you use can supply the requisite amperage or sink it, whichever the case may be.

i am not sure of the small case units, as i only have experience with delco's and some ford products, most of which don't favor direct access to the brushes "and" don't come with isolated grounds (rather they use the case as ground).  now if some of those you have access to have isolated ground posts and ready access to the regulator (like a piggy back unit that can be removed without tearing the units down) then i would expect they could easily be adopted for use in a 24volt system "as is"  just remove the regulator and control the thing as outlined in the white paper and give it a go.  actually if you can remove the regulator and get it to do well at 24volts then there is no need to use two of them to charge two batteries separately so no need for isolated ground either, unless one of the brushes is grounded to the case, in which case that might cause an issue... not sure i would have to take a look at that and think that through.

whatever the intended charge voltage, i think a smart regulator should be part of the plan from the git go... even something as reasonable in price as the unit made by "sterling" proregB i think they call it, would allow for better control, 3 step charging, and some fine tuning ability to match alternator/battery to the available power of your chosen prime mover.

of course none of this is necessary if the goal is only to make a back up charging system, that would likely see little use and only then when you have your eyes on the thing to keep things from going wrong.

i am understanding our dilemma, in that i can't readily source the small case units, and you conversely have issues sourcing the large case units, at least at prices we both can tolerate.

that is probably a good thing in the end because it keeps both sides looking at alternatives and not getting locked into a single solution.\

as for testing efficiency, that gets hairy as hell in a hurry, and it can end up being a costly endeavor in my opinion and likely that of others as well.

simply driving an alternator with an electric motor and then trying to get meaningful numbers from power in vs power out has many issues that likely will just confuse anyone other than an EE in my opinion.

if on the otherhand we had something like a lathe with a variable speed from say 1200 to maybe 8krpm we could simply chuck up the alternator by its shaft, put a torque arm on the case of the alternator, attach a spring scale to the torque arm, and then spin it up, load it down
and build a table of rpms vs torque vs rpm  @ various specific loads such as 500, 1000, 1500... watts output... crunch the numbers and we could get a pretty good idea how efficient the alternator under test is at various speeds and various loads... quite a bit of work but with the right apparatus we could get very accurate and useful numbers i would think.

now i don't have a lathe with such a broad speed range, and i doubt there is one guy in a thousand that has access to such an animal, however one could construct such an apparatus making up a multi step gearing system and a basic head stock to which a shaft and chuck could be mounted...  all it costs is money and time? 

my approach is probably not as accurate, but likely accurate enough for the girls we run with around here.   i use a comparative approach and i will try to explain it in short.

my s195 trigen is fitted with an st7.5 genhead and also twin 555 alternators, of which i can switch in and out each at will, so i can compare various combinations.

the engine iirc has a bsfc of 358gr/kw/hr mechanical and from the engineering books the st type of head is likely very close to 80% and no more in efficiency... we have to go up to 50kva and larger to get to 85% and even that is hard to do without going to three phase.

i run the unit into a fixed load and measure the amount of power generated with a watt/hr meter until i have generated 1 kw/hr, then i measure the fuel consumed by weight in grams, and i also do this at full rated load because it is likely that is where the engines advertized bsfc is rated (more on this if you like later)

it is then a fairly straightforward set of calculations to determine the efficiency of the generator head, and when the field is disconnected i can separate out the windage, friction and drive losses as a subset, but add them back in as these losses belong to the generator anyway...  bottom line the genhead works out to be approx 80% efficient less 2% for drive/windage/friction for a total of 78% efficiency.   because i have ran this test many dozens of times, with various loads, various pump diesel fuels, various ambient temperatures
and the number is always within a fraction of 1% i have a high degree of confidence in the results being accurate... now to prove it out mathematically

in order for the engine to be more efficient the generator would have to be less efficient, neither is likely, just as for the generator to be more efficient the engine would have to be less efficient, equally unlikely in my opinion.

so now i have a pretty good idea that the engine advertized bsfc rating is pretty accurate, and i have numbers on the st head... i can then switch it out and switch in one of the 555jho alternators and rerun the test at 24vdc nominal... apply the known load, measure the power consumed by a digital watt/hour meter and repeat the process... from this and crunching the numbers i found the 555 to be right at 80% efficient producing 28.8vdc at 100amps  or 2800watts/

now the careful reader might ask "how do you compare 2880watts load on the 555 against 7500 watts of the st head"?  here is the answer

i subtract 2880 from 7500 and get 4620 watts, that is the load i must apply to the st head so that the total load as seen by the engine remains 7500watts, and when it is done i find the numbers to work out, and most importantly repeat over and over again.

btw the ge watt/hr meter i am using i can monitor in real time 200 plus parameters, so tracking total watt/hrs and continuous load at the same time is not an issue, the meter will display 6 parameters at the same time.

yes it gets more convoluted, but it does work out in the end.

i have also tested with both 555jho's producing 130amps each at 28.8 vdc for a total of 7488watts and found the bsfc numbers to match that with the st7.5 does producing 7500watts right down to within a gram or two per kw/hr produced, repeatedly.

now just to double check myself i decided to remove the 555 alternator and test using a 4800 series leece neville 175amp unit, controlled by the same controller, same load etc and once the number came in i found the leece neville failing to even reach 65% iirc (its been a few years and i might be off a bit, but my bet is not by much)  this supports my contention that this method of testing is valid and accurate enough for most folks purposes.

afterall that is where the rubber meets the road, that being how much fuel do you burn to produce a kw/hr or electrical power, the more efficient the better the fuel numbers, less efficient and of course we burn more fuel.

while the torque arm method ought to provide exceptionally accurate efficiency numbers, it still come down to how much fuel burned vs how much power is produced, so i am not sure i could avoid using my method even if i had the apparatus setup to do the torque arm type testing.

if that makes any sense?

bob g

[glort]

Thanks Bob for another Very informative and educational post.  Not being the sharpest tool in the shed I'll re read it a few more times to digest it a bit more but great info.

I can isolate the grounds on the alts by using a rubber mounting on one and having it in a fixed position and using the other as the belt tensioner.

I looked at the controller you mentioned and found I can get on here for $200 or of amazon for $88..... IF the mongrels would ship here. They really pi$$ me right off with their moronic shipping policies. Some people can get something and some people 10 miles away can't get the same item.

Anyway, I might pay for one through the nose locally before christmas depending how work goes and have a play with it and see how I go adapting one of the alts I can get by the wheelbarrow load. The one I pulled apart I can get to the brushes on without too much trouble but they are on the regulator box that I couldn't see a way to disconnect from so I might be able to drill a hole right through it to take the reg out and go from there.

One thing that would be good for me with a 24/ 48V system is the ability to use a UPS as the inverter. These have excellent regulation and can be had fairly cheap as well if you know where to look. I have a 3Kw unit that only runs 48V and another couple which are 96v which aren't much good to me.


With the testing you were talking about with a torque arm, to vary the speed of the lathe or driving motor, would a Variable speed  (frequency)  drive be OK to use?

[mobile_bob]

i think a vari drive would be great, especially if added to some gearing to get the range of speeds needed, that would not be hard to do at all if you have access to one.

bob g

[SteveU.]

Well good, good.
At least you two fellows whom I respect greatly as actual DOers of things usable are now sensibly talking in Commons now instead of Differences.

This is still a mighty BIG world we live in yet today. The math/science of it all MAY be able to be duplicateble under artificial set up standardized conditions. But the Real Realities we live in daily are influenced by time, distances, old culture and especially new culture demands that overide any of the "easy" comparable maths of alternative energies.
Means M.Bob for the majorty in this World fellows they WILL will get VAT (social taxed) or equivalent hammered importing anything especially non government favored from non favored places.
Yet they still get access to really nice usable things like slow and medium speed simple mechanical diesels that we here can now only pine away about.
WE get to pay for all of the Tier IV certification costs for far fewer options. Options than now only allow us high speed diesels as new, to have any actual  dealer and manufacturers support.
They for the most part get a huge efficiency leg up right from the get go being three phase higher voltage based for all of thier electrical consumers. We still must muck around with this single phase squishy nuetral ground "Wye" for our personal use comsumers. I read many places this is about an 8% to 20% efficiency loss hole we have to work UP from right there.
I  corrospond with a charcoal/woodgasser developer Brit named Neil Clements. As we contrast and compare these things says he has taken to sayingto me , "Different Horses for different Courses". The wise from at least six different countries/cultures that I corrospnd with I've heard say this same wisdom in different ways. My way is: what you do have local and availble to you has a 3X leg up right from the get go. So for me having been pocket book flattened now too many times to EvilBay ANYTHING anymore it must be at least 4X as good the Local available by my judgement.

Ha! As the dedicated 12VDC system user here I am butting out now since you fellows are on to higher voltages.
My point had been do not knee jerk sell these newer dual internal fan auto units short untill you have actually used them.
Just both of you realize that for us us raw stocks motor fuelers we are always requiring some form of user dewatering, refining, purifing and consentrating so there is no such as waste heats. Even belt drive BTU's can all be used somewhere in a useable fuel making process. The only watsted watts are those you did not put to some useful work. Northern or Wet Cold Gray world living always needing heat; the only wasted watts are those YOU allow to blow away unused in the wind. Even the dog house, chicken house, pump house could benefit from a few watts of heat.

I will not be selling off my Trace SW 2512 anytime soon. It's previous owner and his wife used it quite happily fully off grid distanced for 10 years for all of thier needs.

Glort the "delays" for 42 volt Auto implimentation was first primarily the mulitcell battery costs and durability issues for the batteries and ALL contactors in the switches and relays. Then a world wide 4-5 year economic meltdown wiping out the biggest pushy players for this like General Motors. And now the realization of just how incredibly expensive it will be to change the whole replacement supply chain down to the last bulb and switch.
Dosn't matter anyhow. Takes at least 10 years of 7% a year replacement deployment until the actual hardware is widespread and common enough to be affordable to us common folk for DYI use anyhow.
The wisdom is in a song,
"When you can't have the one you (would want to) LOVE,
Then love the one you got!"

Best regards to you both
Steve Unruh

[glort]

I think there is a lot to be said for the 12V system but what Bob says is undeniable in that the off grid development is going in other directions. 12V is great for adaptation of Automotive/ Marine parts but once you go outside that, it's pretty much on it's own. I like 12V as I have access to a wrecking yard full of 12V components but as soon as you need to go to mains voltage, it's just too much of a jump for other componentry.

Like I mentioned with UPS units. The smallest I have are 600W units and even they work off 24V.  you don't need to g much bigger and the voltage jumps to at least 48.
Here ( like the UK) our standard outlet is 230V, 10 A and a standard circuit is 15A.  230V is 20 times 12 so to go to 24 and reduce it to a 10 times multiplication or up again to a 5 times upscale is a heck of a lot easier than dealing with the 20X multiplication factor.

there are lots of 12V inverts I have seen but again, once you go to anything that resembles the output of a mains socket, the input voltage jumps to 24V. 150A on 12V is a lot of current but when it's in mains voltage, there are still a bunch of everyday appliances that would not be able to be run on that power level.

Things are certainly different around the world.  You get screwed on the engines you can have and the emissions, our entire population is brainwashed to think anyone that wants to own a .22 rifle must be a psychotic mass murderer in the making and should be treated as one.
Don't even get me started on politics that I regard as the biggest idiocy mankind subscribes to.  It's joke and a con the world over as far as I'm concerned and this is why we have these stupid regulations and restrictions of our liberties.

That said, at least you don't have the stupid carbon tax crap that the greenwashed morons imposed on us. In a nut shell ( and I have looked into this thoroughly rather than get my education on it from the media)  This is a tax that costs billions but 94% of what is collected is paid back to businesses and households to off set the cost of paying the tax in the first place!
It seems stupid beyond belief typing it but that is exactly what it amounts to .  Take out what must be massive admin costs and it's no wonder that it is impossible to find one single solitary statement from the gubbermint as to what is specifically done with this money designed to save the planet.
You Americans seem to have some stupid rules and regulations but I reckon you'd be hard pressed to beat the lunacy of our carbon tax debacle!

As for the 42V system, right from the first time I heard about it I thought what a nightmare that would be. The amount of parts and infrastructure that would take to get off the ground would be massive. Buying a lightbulb or simple electrical component would be a nightmare for years.  Having to restock a line of batteries would be fun as well and so would the results of people that bypassed whatever safeguards that tried to prevent a 42V battery going into a 12V system.

Dealers would be the only ones that carried a lot of parts to start with and no doubt the prices of those would make gold look cheap and it would take  a good 10 years before the demand was sufficient that they were available as widely as 12V components.  As for DIY, I think it would be 15-20 years for us here in the colonies.

Of course then you have the nightmare in the accessory market. " Did you want those driving lights and stereo system in 12 or 42V?"

[glort]

I was enjoying a bit of DIY mental therapy today and fired up the China diesel with the twin fan alternator on it.
I went looking for another battery lead and saw in the box I brought back from the wrecking yard there was a plug for the alternator which had 3 wires instead of the 2 the one I was using had.

I took the twin lead plug off and connected the triple plug and tried shorting the wires back to the positive terminal. When I got to the 3rd wire that was absent on the other plug, the motor bogged down and stalled. The inverters I had connected to the battery also tripped out.
I restarted the engine, took it to full power ( 6 HP) and with one eye on the VOM, put the lead back on the positive terminal and saw 19V on the battery before the engine promptly stalled.

Did this a couple more times to confirm the results with the same thing happening.  It looks like the 3rd terminal of these alts which are from the later model alternator  computer controlled cars have the wire that one would need for a remote controller.
I tried putting the lead back to positive through a tail lamp and while the engine stalled slower, it still loaded down.

I saw a vid on youtube the other night where a guy has some power resistors he clips the lead from the alt to in order to control the output.
Would anyone know what sort of wattage and resistance would be in the ball park for an alternator to do this with?

If this wire is the wire needed for a controller, then I think these particular small frame alts might just be the jackpot for DIY battery bank chargers.  Could be no mods are needed at all, just hook up the wires.

I tried to measure what the open circuit output was with the battery disconnected but the engine Dipped and the field seemed to crash  before the thing could get any power up. It may have been something to do with the reg or diodes still being totally intact and creating some overload protection.
This makes me wonder if the alts would go to higher voltages with an external controller or not.
I was wondering about connecting the alt to a couple of batteries for 24V through a fuse on the output leads so as to limit the possible escape of any magic smoke.

In any case, it appears these alts could be dialed up to produce a lot more amperage on demand even with the addition of a simple resistor on this wire.
Higher voltages may require some modification but it seems at least the field coil wire is there for a controller.

[thomasonw]

Glort,

Thank you so much for following up and posting your results - there is a LOT to read here, and I still need to plow through it.  However, one thought does come to mind:  When talking about 'burning up' standard small frame alternators, I know in the marine world those words are usually associated around some 'hot rodded' alternators, like what the buzz car kids use - pulling out 150A or even 200A out of a small frame alternator to drive their monster audio system - for a short while  .  Today we motored for 6.5hrs pulling 195A on average from our LN4800 series alternator - that I suspect would be a different story then the load you were seeing.


But, I think you make a huge valid point - cars these days have a massive electrical demand to even 10 years ago.  And as such, to deliver 40-60A continuous is not unreasonable.  Taking a series of these $ / handful alternators sure does seem attractive vs. spending $$$$ on another solution.

Thanks again for sharing!  And looking forward to reading all the rest of this thread.
-al-

[glort]

Good to know someone is reading my rantings!

I have seen those mega alternators on the net. 5x 300A alternators all strung together.  Must take near 50 HP to drive all that. If they do get them to full load, I can only imagine the single serpentine belt they use can't last long! Apart from the load there is all those bends and turns which lower the amount of power the belts can reliably drive.
Apart from that the belts must be 25 Ft long!

I guess if you want anymore than about 175A which you could get from these alts comfortably using 2 of the things then the bigger alts would be better although many I am seeing now on the latest vehicles go to 200A stock.  2 of those and you are at 400A which is a fair old belt to put into any battery bank.

Running 2 alts at less that flat out load would also be good for preserving longevity and with the price of the things, is entirely practical to have 2 units and 2 spare as well.
Also running 2 alts flat out is going to bring the charge up and reduce the load a lot quicker than just running 1.  And then there is of course the redundancy if one does go south.  I would tend to think that a lot more likely through wear in the brushes than any other fault.


I'm pretty convinced that the lack of engine bay heat gives these things a Huge shot in the arm as far as pulling full loads.  I have been playing with my sons car the last couple of days which has the same alt I'm playing with fitted as OEM.  Seeing how hot the alt is through under bonnet temps cruising around in the day time with no substantial load, from the quick touch tests, I'm pretty sure the alt on my stationary setup didn't get that hot when I was trying to overload the thing.

I tried playing with the alt again today and using what I think is the control wire through  1/4W resistors which was all I had. I didn't look at the rating, too lazy to squint that hard to try and make out the colours.  I wasn't expecting anything to happen but with one the thing bogged the motor down again and the other had no effect so was obviously a much higher value.  I was surprised the first one did anything as the leads on those resistors are so small as to be a resistance in themselves to any meaningful amps.

I hope to get a controller before christmas so I can hook it up to this 3rd wire and see what happens. I have tried not too hard to find what the wires do but all I have found so far does not correspond to the wiring colours on the plug I have. The descriptions seem a little questionable as well.
I'll get the alt number and try a specific search on that.