12V Alternator Conversion

Sorry I misstated it. What I meant was the turns per volt ratios not the primary to secondary ratios change.

I caught that later when I reread my post but this crappy web site format does not allow changes after a short while and I couldn't change it.

More of a question then a statement, but shouldn't the capacity of the transformer be reduced at higher frequencies due to the increased inductive reactance, at higher frequencies.

Hello again tcmtech

When I sent my #22 I hadn't checked it was you who commented about the higher speed needed!

You also said "Plus the output amp limits are still the same within reason." Do you know you happen to know how the current limits itself?

As I'm sure you know, the old dynamos had no such self-limiting characteristic. The (electromechanical) regulator had separate coils for current and voltage (combined into one on earlier versions, but the effect was the same). If you disabled the regulators (eg by poking a match between the armature and the electromagnet) the amps and volts would rise drastically if you revved it, and soon burn the thing out. But alternators only have voltage regulator.

I've asked several electrical engineers this over the years and though they'd waffle a lot, short answer is they don't know. 2 - 3 years ago there was a thread on alternators on this forum and I raised it there. Got some responses, but none that I found convincing.

Cheers.........Codey

Rewind is VERY difficult unless you already work at a motor rewind shop. Either find one with the correct output voltage, or get a DC-DC converter to step up the 12v to 48v. Most modern converters are very efficient.

You state that this is an electric vehicle project. What is turning the alternator?

I worked in the manufacturing of diodes for car alternator (TVS Lucas). If I am right the new car alternators/ DG set alternators generate 110V AC 3 Phase in Delta configuration. A 3 Phase bridge rectifies converts to DC and it is further voltage regulated and 12V for battery charging etc. Hence check your alternator once again. If it is giving surely 12V DC then easiest way is to buy one SMPS based DC - DC converter 12 to 48V.

Alternator has some (1-6) diodes. You must uninstall the diodes at first. Then you can make circuit attached to charge you 4 batteries (4x12 volt= 48 volt) directly..

(How can I submit the circuit picture ?)

Best Regards,

Sutisno,

e_mail: bogor35@yahoo.com

I hope we are thinking of the same; I'd recommend Catboy to

1.-Bypass the rectifier bridge and save it.

2.-Get a 3 phase transformer (0.75 KVA) that has a turns ratio of 4:1 and...

3.-Conect the lesser turns winding to the alternator's output (even older alternator types are 3 phase), and then...

4.- conect the rectifier bridge to the transformer's output (which is the transformer's side with 4x winding turns).

Yahlasit

Look in to marine alternators. A number of seagoing vessels use 48 V systems, and you should be able to find a 48 V alternator in that arena

Using an external regulator, drop the voltage feedback to a 1/4 of the original with a resistor network and you will get 4 times the voltage out!

Sounds like a good idea, but there's no need to use an external regulator if an alternator with external (battery) sensing is chosen. In that case the reference voltage input wire to the regulator is accessible and the voltage divider can be put in there.

I don't know offhand the resistance of the voltage reference input to the regulator, but it must be quite high as on battery sensing it's permanently live but doesn't run the battery down. So a high resistance can be used for the voltage divider. Be a good idea to find out the regulator resistance and make the divider resistance at least 10 x smaller.

Cheers........Codey

Even if the AC output of the alternator's winding (before the rect. bridge) is only 14V/Krpm ?.

Then we should be able to increase the DC voltage to whatever you want, with no limits!!

Yahlasit

That sort of works but the voltage raising limit is very low. The stock internal regulators cant dissipate the heat from dropping a much higher than stock voltage down for the regulation system. A separate power source with the original voltage is needed to power the regulator and rotor field. Or a big power resistor is needed to get the input voltage that feeds the regulator circuit down to its acceptable voltage range.

I've tried it and learned it from the smoke 'em up way.

And yes the sensing current draw is small. In the few Milli amps range typically on most alternators with a remote sensing connection.

OK tcmtech thanks

I've never tried it so you're ahead of me there. But couldn't we put a voltage divider on the field supply also, to reduce it to ~ 12 volts, or something in between? Thinking about it, putting 48+ volts on the field coil (at full excitation) has a good chance of burning it out.

As other posters have said, output is 48 volt only at highish rpm, but not impractically high (according to my estimate)

Cheers..........Codey.

In its stock form the rotor field coil typically cant take much over its stock rated voltage without overheating and burning out. Most alternators use a separate set of diodes that draw power off of the three phase output before the main rectifier Assembly so if you were to unhook that supply line and then either use a independent power source, a regulated power source derived from the 48 volt output, or a simple inline resistor to limit the incoming current to the regulator you could get the higher output with very little additional parts.

And as has been stated by others if the field power is held constant the alternator output voltage will get higher as the RPM's are increased. I have been reading up on some other sites and apparently many alternators can get outputs well over 120 volts DC when spun at 15000+ RPM.

If you did try it I would start with the assumption that the rotor field coils are roughly 4 ohms and thusly draw about 3 amps at 12 volts give or take. If you just went with a single inline dropping resistor to limit the input current to the regulator from your 48 volt source you should be able to get by with a 12 ohm 50 watt resistor. That should reduce the incoming voltage to the regulator input well enough for it to handle working with a 48 volt system. The GM Delco SI series alternator regulators can take around 20 volts input without burning up. So if you were to size your resistor to stay under that peak you should be okay. Ideally keeping the regulator input voltage closer to the standard 14 volts or so is better.

Then as someone else had stated it would just be a matter of using a voltage divider to set the reference voltage input to the correct level to get the right output voltage you need. Given a 12 volt automotive system actually runs at around 14.4 volts on average your 48 volt system will actually need to run around at 57.6 volts when charging.

A little experimenting with the exact values of the resistances would likely be needed but realistically you should be able to make something functional for fairly cheap.

And yes the output voltage will drop off rather quickly being the alternator is attempting to put out higher than originally designed voltages. But still with a high enough RPM it should be possible to get near the full amp rating out of your alternator even at 48 volts. Plus also consider you do need four times the input horse power to do it.

Unless the alternator was designed to be spun at 15,000+ RPM in the first place doing so to push out eer voltage is not a sound practice. The centrifugal forcese on the fingers of the rotor pole pieces will exceed the safe limit.

This whole discussion has devolved into a theoretical paper exercise of questionable practicality. The OP just wanted to charge a 48V battery pack for an electric moped. There are better, less time consuming and most likely less expensive ways to achieve this end. Someone did ask a pertinent question which OP never did answer. What is going to turn the alternator if the vehicle is an electric drive moped?

Many cars have around a 4:1 or even higher pulley ratios on the alternator. My car has a 6000 RPM red line and so does my pickup and both have around a 4:1 gear up from the crank shaft to the alternator. I think the puts 15 K RPM well within the realistic safe working band of a common alternator.

Any competent auto tech can confirm this is a realistic ratio as well!

Maybe you are right. My ford truck only has a 3:1 ratio and I am more familiar with real alternators having a decent output. The kind I normally deal with have smal sizes produce 100 Amps continuous output and go up from there. Medium and large frame units should not be spun above 6000 RPM because the centrifugal forces tend to distort the pole finger pieces. And the output curve tends to flaten out just above 5000 RPM. With clearances measured in a few thouands to start with it doesn't take much to cause an interference hit when speeds go above 10,000 RPM. I normally replace 55A alternators with real units and use the 55A units as paper weights or door stops.

Excellent paper weights....pretty too.....

Hello catboy:

While I am waiting for a reply from a member that is knowledgeable in this area I'll take a chance on sticking my foot in my mouth.

The alternator is capable of putting out 48 V fairly easily, although I can't say how long it will live with sustained high voltage output, I don't actually think it would be a problem. In actuality you will have to be putting out somewhere in the neighborhood of 53 V to charge your batteries depending on the rate of charge to want.

Several years back I built a portable 12 V battery charger with a Briggs & Stratton three horse and a 100 amp Dodge alternator that was salvaged from a wrecked police car. Worked like a champ with the two wire electronic regulator, I also set up a rheostat for adjustable output voltage.

The only problem I had was I needed a larger engine to fully load the alternator, I had intended to make it a dual purpose battery charger/ portable DC arc welder.

I'm not sure of the project that you're doing, but you could easily investigate the feasibility of this in the same manner. Whatever you do you need to get a alternator that utilizes a external voltage regulator to be able to control the output.

One possible wiring scheme would be to read the voltage from a single 12 volt battery in your 48 V battery pack, while still charging in series , probably some drawbacks to that but it just could work.

I'm not sure whether the 13 1/2 volts that would be available from a single battery would sufficient to excite the field to provide the desired output.

Automotive alternators are internally 3-phase generators.The three phase power go to a 3-phase bridge rectifier to generate the 12 V( actually up to 13.8V.

The rotating field of the alternator is controlled by the electronic module which monitors voltage and changing current so as to limit the field current of the alternator and avoid damage from overcurrent.

If you could get a 3-phase 12 to 48 V transformer , you could build your own charger or buy an off the shelf rectifier unit , that would have sufficed.

You would have to get inside the alternator and tap off the 3 power phases before the bridge rectifier.

Alternatively without modifying the alternator, you could get a cheap inverter which converts the 12 VDC output of the alternator to 48VDC.

Good luck.

Ever thought about having a switch to make the four batteries in parallel just for charging, then you just need an alternator with a heavy current output.....or even parallel 2 at a time and charge from a 24 volt alternator from a truck!

Charging 4 batteries inseries, especially if car batteries, can bring a lot of problems with it, it is not to be recommended.....

Also discharging too far for any one battery will reverse polarize it and ruin it....as will happen as no two batteries are ever completely identical.....

I would like to second Andy's comment. Charging batteries is a very finicky business. In a 12V automotive system there is a constant load placed on the battery and that helps keep the voltage down. In a purely charging situation, using a non standard voltage, what will you use to stabilize the system?

The difference between a good charge and a boiled battery is less than a volt. Unless the challenge is to built it yourself while not spending any money, buying a purpose built DC-DC converter with a regulated output set to charge a 48V battery is the safest. Now if you have unlimited access to batteries and can affod to smoke a few, by all means go ahead. I found by accident that a resistance placed between the regulator negative ground point and the battery ground point is enough to raised the charging voltage. It is in effect the same as the voltage divider suggestion by another poster. Experiments with a variable 10 Watt wirewound resistor shoudl tell you what value is needed.

Field current in most automotive alternators is limited to 5 amps. Voltage is not critical.

Also keep in mind that as you increase the voltage output you must decrease amps by a corresponding amount. The target is to end up with the same watts. Ignore this and you wil fry the stator windings or the diodes or both.

If you have money and equipment to burn, go ahead and experiment. If money is tight and the development of an electric bike has more priority; go buy a 5 - 10 amp output DC-DC converter. It will be cheaper and faster results in the long run.

Everyone has good information for your problem. It is always best to keep it simple when possible. In this case you most likely have some sort of 115 volt charge you are now using. I would go buy a Power Inverters to fit your need and pocket book. Harbor freight had a good number stating under $8 all the way to $600. Plug in or hook up the power inverter plug In your 110 - 120 volt house charger and start charging.

Advantage is power inverter can be used for other stuff like laptop computer, lights, radios, other voltage transformers like to charge my cell phone. I do not need a car charger for my cell phone I plug in my 110 volt house charger in my car and away I go. A hole lot cheaper than the auto one's the cellular dealer sells.

Call Electrodyne 800-341-0242 | 207-883-4121 in Portland ME. They build/stock 12,24,32,48V alternators. no need to do all that work to a 12V alt. when you haven't even bought it yet. Get the right part to begin with.

Oh right! Have you looked at the prices for a good Electrodyne lately.

The man needs a $50 charger and was maybe willing to spend $100 on a modified unit. Everytime I ask for a quote on Electrodynes they cost hundreds and in some cases thousands of dollars for a nice hefty unit. I spec them for marine applications in ood ball voltages.

Gentleman:

I think this would be a good time to second elnav's request for more information.

Four possibilities come to mind for this application. A gas electric hybrid, regenerative braking, portable charging station, and last but not least perpetual motion, I fear there is a possibility that we've been chasing a wild goose.

You forgot HHO!

Thank you all for your inputs. My project is a very small city vehicle, 2-seat, 4-wheel with 2 permanent magnet 48v wheel motors of 2000w each. For the first prototype, which is only for geometry and steering as well as drive train testing I intend to use 4 x 12v lead-acid batteries, but later LiFePo4 when they come down in price. The vehicle will be designed to EU moped regulations giving freedom from taxation and congestion charges here in Sweden. It will be a plug-in but it needs emergency charging possibilities and for that I have a 4-stroke 2.5 hp Honda. I would like to be able to use a normal (but voltage converted) automotive alternator, hence my query. This is a one-man project and will take some time. catboy

I am sure that I speak for most of us here in wishing you every success in your project and please do keep us informed of progress, with photos as well if possible.....

I will repeat that my early tip to switch the batteries to parallel (with isolation diodes of a low loss type) and charge from a 12 volts supply (actually 13.2 volts which would never overcharge any of the batteries and need not be temperature compensated for either!).

The car alternator would probably supply up to 14.4 volts, so precautions against over charging need to be made. A simple check with a good voltmeter would probably suffice and not leaving the batteries charging on their own for too long, especially not the first time.......

Remember that normal car batteries do not like being over charged, or left under charged for long. The worst you can do is to empty them almost completely! They die a quick death....

Leisure batteries are far better for most things, except for car engine starting as they cannot deliver the massive currents needed as well as car batteries do....

Hello catboy:

Let me first apologize for having misgivings, your application sounds like a innovative way to facilitate your project.

The additional information was quite useful however. This is very much along the same lines as something I've already done as far as using a small engine to drive a alternator.

One thing you may encounter is that the alternator will be rotating in the wrong direction, this was the case when I use the Briggs & Stratton to drive the unit I had made.

As far as electrically there was no problems, the problem is of course the cooling fan will be running in the wrong direction. I've heard that there are some bidirectional alternators available, and of course you could solve the problem with either a jack shaft, or merely use a small electric fans to provide the cooling for the alternator.

One other thing I remember from the project is I ended up under driving the alternator, I don't have any exact figures but I believe it was somewhere around 40 to 50% under driven i.e. my 3600 rpm engine turn the alternator at about 2000 rpm.

Andy's idea of charging the batteries in parallel sounds like the simplest solution. If you were to utilize this scheme a standard 12 V alternator and regulator could be used.

Wish you well with your project, keep us informed.

Interesting post......

What I believe I neglected to mention properly in my earlier post was that charging each 12 volt battery in parallel, allows each battery to charge fully and equally. Each and every battery is an "individual" and has individual "needs" so to say, this way that will be catered for....

In series (at 48 volts), this might not be the case...and could lead to further problems.

This is often the reason that golfing trolleys need a new battery set far more often than should be theoretically required......

Hello Andy:

I'm thinking with your arrangement utilizing diodes that is that there would be no reason not to leave them in series for providing power for the vehicles motor, while charging them in parallel. Not quite sure about that though.

You did bring up a good point about equalizing the batteries, to do that obviously they would have to be a switching mechanism to charge them one at a time otherwise the first battery to come up to the correct voltage would satisfy the regulator.

Got a run, heading to Vegas, I'll see how you guys have done in a couple of days, no room for the laptop on the motorcycle.

Slight error in thinking if I may be so bold.

The battery with the lowest voltage (which also means the lowest charge as well!) will draw the most current for charging and keep/hold the voltage lower.

As its charge increases, so will its/the chargers voltage rise till the next battery also takes current, then the next and then the last. Then they will all charge together......that is assuming diodes are installed to prevent a higher charged battery from charging a lower charged battery.

In practise the charge on a LA Battery is conversant with it's (or the charger's, depending upon how you see it!) voltage.....lucky for us all. If it was a current charged battery like NimH or NICADs, life would not be so easy!!!!

A LA battery is charged by the difference in it's terminal voltage and the charger's voltage, allowing current to flow.

No difference in voltage = no current = no charging! Which is why the charger's voltage must be higher than the Battery's.....

I hope my very simple explanation offends no one......as I have, for example, completely ignored the effects of temperature on charging amongst other things!!!!

Andy your description is correct as far as it goes.

In the real world once you get past the first few cycles lead sulfate begins to accumulate in varying amounts on every plate. As you probably know, lead sulfate hardens over time, even when the time is only a half day or so. Lead sulfate is not conductive. At first the surface charge builds up slowly when all area of each plate is fre of lead sulfate. But once it does accumulate, you can get a surface charge that rises up to the peak voltage quickly while, the deeper inner layer of each plate is not yet fully charged. This shows up as lack of capacity despite the fact th evoltage reads high and implying full charge.

Unfortunately the single stage regulator in an automotive type alternator will only see this surface charge voltage level. And as you correctly explained the charge current is a function of voltage differential. This is why a sulfated battery will not always accept a complete charge. Wiring the cells in series forces the same charge curent through each cell in turn. This results in a more complete charge.

Wiring batteries in parallel means the cells with more lead sulfate will quickly rise to the high potential and stop accepting a charge current. Result; less than a full charge. If you run a timed charge cycle, the higher voltage on some cells will now begin to create gassing ( bubbles) and in wet cells boil of the electrolyte. In wet cells this is not especially harmful but in (SLA) sealed lead acid batteries this is destructive. The vents release the gas but there s no way to refull the lost electrolyte. For this reason sealed batteries must not be charged to as high a voltage. The maximum voltage must be kept below the gasing point.

In a parallel configuration each battery may have a slightly different potential. As you know, the diference between gassing and not gassing is less than half a volt.

Good quality mains powered chargers have a 3 stage charging regime for just this reason. Normal automotive alternators do not. Only those modified with special 3 stage regulatos come close to what the mains driven chargers do.

A lot of what you write is true, but is mainly only with car type LA batteries and then when mixing ones of mixed parentage or age or use......

Which is why a good system will only use Leisure type that accept a lot more misuse with no problems.....and tend not to sulfate until much, much older......

I was also assuming that the four car batteries were purchased together, from the same manufacturer, from the same lot and used/charged together since then. This would equal out the sulfation/damage and keep things on a more even keel so to say.

I agree that even "identical" batteries have minor differences and that is why the parallel method is better (with isolation diodes) as when the voltage is over 13.2, all are at an almost identical state of charge.

Forcing current through 4 batteries in series means that when the first one is charged, it has to gas and gas till all the other three eventually play "catch up"......this is the reason why golf cart batteries have such short lives......not to be recommended at all......over charging not only gases a battery, but also damages it, reducing its useful life.....car batteries are relatively sensitive to both over and under charging.....

When discharging a battery, one must make sure that the weakest cell/weakest battery, is not discharged too low as then the cell is reversed polarized by the cells that are still charged and delivering current. This cell(s) will fail rapidly (especially in car batteries) and eventually not accept any further charge or supply any further current. This situation also needs to be avoided...........

Remember batteries fail cell by cell, not battery by battery, but as 6 cells are combined in a single battery, all 6 need to be replaced when one fails......

By the way, charging does not get rid of sulfation as many people think. One of those special chargers with the high current reverse pulse every few seconds appears to help in that area......or one of those separate "zappers" that one can buy......I use one on my caravan battery and it is 7 years old, hardly uses water, because I only charge it to 13.2 volts......and it has a good "Zapper"!

Though Zappers are not scientifically proved as far as I am aware, but appear to help.....

In a partially perfect system, each battery will have its own charger with electronics to make sure that it does not get over charged.

In a REALLY perfect system, each cell in each battery would have its own charger, but that is over doing it!!

In the RN, we had LA batteries in all sizes up to several hundred amps per cell (Subs) and we also had a 2 week training course in their care and maintenance, I have never forgotten it.......the technology has changed very little since luckily for me......all I can say is that many things are wrongly understood and talked about with regard to such batteries.....and many fallacies are propogated.....

I hope this helps a little further.......but please feel free to ask or question anything that I have written....I hope that I have managed to write it in such a manner that makes sense....

DEAR ANDY,

PLEASE TRY TO BYPASS THE REQULATOR YOU WILL GET 110V 3PHASE THEN USE REQULATOR 48V I THINK THIS BEST WAY TO FIND SOULTION

What are you talking about??? Please explain as my last post was July 2009........

Recently I have connected up with someone who actually understands alternator design and charging systems. He also has a diesel test engine driving multiple alternators all of the same frame size but configured differently to give either 12V or 48V. He says yes you can let the open voltage rise higher and regulate a 12V Alternator to produce 48V BUT!!! the trade off is you can still only get the same wattage or you risk over heating the stator windings. So for a 55 amp 12V alternator you only get 13 amps at 48 volts. He has access to a rewind shop and does rewind stators for higher voltage and has to custom build regulators to suit. But in most cases the higher voltage does require greater cooling . Therefore it is not a trivial exercise to get 48V from a 12V alternator.

Catboy, there is one difference between your setup of just driving an alternator with some form of engine and the automotive system where the engine and vehicle electrical system is connected.

In a vehicle the engine's ignition system uses at least 5 amps of load current, some of the newer electronic fuel injection systemes use more. In addition there are headlights, marker lights, and sometimes an entertainment system or heater or air conditioning.

These all tend to pull down the higher voltage of 14.2V to a more reasonable lever of 13.8 - 13.2V thus avoiding the damaging high voltages of 14.2V which can caue an SLA battery to outgas. Very destructive to SLA.

In your intended application there is no such load to bleed off the surface charge that naturally occur on any lead acid batery. An automotive alternator normally does not come with adjustment that is accessible by the user. Especially not the smaller sizes.

In my marine work we typically toss away the single step regulator and substitute a 3 stage regulaor which does have a full range of adjustments including voltage and current limiting. Not to mention which, temperature sensors can be fitted to compensate for battery heating or warm ambient conditions. However such regulators are not cheap.

Andy's suggestion of charging the four 12V batteries in parallel has merit in that it uses a normal 12 V alternator. One little detail does pose a potential problem. Four parallel charging paths will This means in practice that the batteries do not get exactly the same charge. A single stage alternator will regulate on the highest voltage seen. When you parallel the batterie, one of them will always be short changed. This in turn means it will accumulate a bit of residual lead sulfate each charge cycle. This lead sulfate in turn raises the internal resistance and the effect becomes cumulative.

For this reason most high end marine systems using 24V have four six volts batteries in series. 12V in series also work. But we never place 24V battteries in paralle if we can help it.

Batteries in series all see the same charge current. (Kirchoff's law) that in turn means equal charging for every cell. Your idea of going 48 volt is good and represent the best way to do it. Which is why solar, wind, and micro hydraulic generation all tend to go that same way. In the utility power industry we used individual 2V cells all wired in series to give the required DC voltage for station back up. This is still the preferred method for most industrial applications.

Since you were contemplating the purchase of an automotive alternator, I assume you have a budget in mind, no matter how modest. For the same money or maybe less, you could get a DC - DC converter. In Europe I would be looking at Victron or Mastervolt or possibly BEP as the BEP is NewZealand but do have a European distribution presence. I often specify their products for boats intended for European build and or use. In boats we use the DC-DC converters to stabilize the halogen light circuits.

You can scrounge a good used alternator from an automotive scrap yard for a lot less than buying new. Any garage can clean it up for appearance sake. For a show and tell prototype this aspect is important. Drive it with your Honda engine and feed the 14.2 Volt output to the DC converter. The converter in turn has a regulated and usually adjustable output voltage to accomodate SLA or Flooded batteries.

I built a Yanmar engined power system for similar reasons. The small 100A alternator is a Balmar that I happened to have kicking around the junk box and so is the 3 step regulator. That is how I learned of the pitfalls of such systems. Fortunately the Balmar regulator is adjustable as well as current limited. The charging station is simply a means to an end, not a project goal in itself. Hence my suggestion to do it the least complicated way. No point in spending time on it instead of the actual project which is the moped.

Another thought. If you have not bought the Honda engine as yet. Consider buying one of the Honda generators like the EU1000 or 2000i gensets. Possibly even cheaper at a garage sale. Very quiet and has other uses as well. Mount a 48V mains charger with it or use the same mains driven charger you are already planning to use. This setup uses off the shelf products, is readily available and in the event of a failure is repairable quickly by any service shop. If your custom built/modified unit fails, only you will know how to fix it and you may have bigger issues to deal with at the same time.

You have written an excellent post with a lot of good infos, BUT, I have to take you to task on one point. You wrote:-

Batteries in series all see the same charge current. (Kirchoff's law) that in turn means equal charging for every cell.

This is only true once (in this example) the 3 batteries with the lowest charge have "caught up" with the fourth battery with the highest remaining charge.

Remember, each battery has depending upon its charge a different resistance. Kirchoff's law is talking about 4 resistances of the same value in the example you quote.

The voltage of the system (charger) will be dropped by the larger current draw of the least charged (lowest resistance) batteries.

To test, you can place two batteries in parallel, with diodes to stop one charging the other, and measure the terminal voltage of both as charging commences......the lower charged one will "hog" the current till its voltage is the same as the other battery!! Then both will charge in parallel!!!

Every textbook on basic electricity I have ever seen has different resistances in the series circuit used to teach Kirchoff's law. In fact most exercises require th estudent to calculate the voltage drop for each resistor when the resistance s do not mathc.

The current is the same in all parts of a series circuit. The voltage drop varies.

For parallel circuits the current wil divide inversely according to each resistance in parallel. In other words the most current will flow in the lowest resistance path and the least current will flow in the highest resistance path.

Since it is the current that actually does the charging of the plates, the battery with the least internal resistance will hog the most charge current. During the latter stages of charging, all the batteries will appear to have the same high voltage. Unfortunately this is not a measure of how much of the charge current each battery has absorbed. The voltage is more of a surface charge.

At present time we do not have a low cost easy way to measure how much lead sulfation still exist on a battery plate when the voltage reads 14.2V for example. The Midtronics meters are very expensive. They measure internal battery capacitance.

What you have written here is fully correct, what you wrote before was not!!!

Send us your requirements of 48v alternators ranging from 15Amps - 55 Amps at r_d@jumpsindia.com we will sort out your all problems immly.

windblue.com sells unregulated perm magnet alternators GM 10si and 12si cases. - about $250. might be able to buy windings from them also.

Any idea how these permanent magnet alternators are regulated. When I looked into this a year ago none of the available manufacturers could promise regulated output that would not boil out flooded wet cell batteries. The One exception being Polar Power. however pricing began at $10k for a modest sized generator power plant and eCycle who sells kits wanted $900 for software development to refine their product to be suitable for battery charging.

How about cannibalizing a 48volt wind turbine unit? size weight and output falls into the output range you are looking for.

Enav ,

Most designers that I know, regulate their power through a stand alone controller. We sell then in several sizes but, I think you would need the 100 amp unit with the windblue alternator , about a $300+/- unit.

Best Regards,

Joe Woodall, Managing Partner

Georgia Adobe Rammed Earth & Renewable Energy

http://www.georgiaadobe.com

Thanks for the link Joe. Got your website bookmarked now. Unfortunately I did not see the Windblue alternator. I did see the controller you mentioned but found no link to detailed specifications. The purchase list includes load resistors leading me to think it is the same as the controller style that switches to a dump load when the battery voltage reaches a certain threshold. This is precisely what I did not want. I see you list Xantrex among your product line. I am familiar with these having worked at one time for Xantrex as an applications/sales engineer.

Elnav,

We don't sell the Windblue product line. Someone told me once those guys are rebuilding automobile alternators ( I hear perhaps from used parts sometimes so they paint them ). It's a specialty market, designed for the more inexperienced client , for slower turning home builder of wind turbines , that perhaps don't yet know how to wind a coil.

We sell products for that other crowd , power systems that are designed to run flat out "24/7", making power without quitting. That's the double bearing brushless alternators, that we list if you want 24/7 power , when coupled with a prime mover. The controllers we sell are good pieces of equipment ( tested ) and power diversion is the most practical method of load correction, that I depend upon myself, so we stick with it since we know it and we don't really get off into the other possible methods, in our product line offerings.

XANTREX Equipment is perhaps the best know ( Advertised ) product line we sell but, it is so competitive on our end that I'm sure you can find better prices than ours, as we just don't try to become inexpensive prostitutes; We would rather be thought of as a Good Quality Whore.

If I can help you, just let me know !

Joe

I don't like being a pimp in the prostitution business either which is why I now work independently, not for Xantrex. :-)) The original post was asking for a 48V charging source of approximately 55 amps. the implication being the prime mover in this case is either a fossil fuel ICE or maybe kinetic energy driven by the moped itself. As long as there is a connected load to bleed off high charge voltages and prevent battery gassing things are fine; but in many battery charging situations there is a surplus of energy being generated and a dump or diversion load is not a a good option. Only for wind or hydro power. In my designs there is a need to finish the charge as a float voltage not at full absorption voltage. dropping the voltage towards the end of charge cycling is essential to prevent buildup of lead sulfate so reaching float stage and holding it there for some period of time is essential. If the alternator is driven by a prime mover that is also used for some other purpose fine control of the charge voltage is essential. PM generators are more fuel efficient than the more traditional alternators but they do not seem to have the same fine regulation available as yet.

For these PM versions, frequency is a matter of how quickly you turn it, also voltage is so decided. Not an easy decision for you!

Agreed! Which is why I was asking for fairly sophisticated regulation from the PM generator people. You can invoke the I squared R law and make an argument in favor of a 230V genset. however I have rarely seen any IC engine optimized for torque peak at 1500 - 1800 RPM unless it has an extraordinarily long stroke. The lister clone engine on the Georgia Adobe site may be one of the few motors that might qualify on that count however the vertical height of it would preclude installation on most of the projects I get involved with. A DC genset is the best compromise in that it will allow variable speed to match load, and selection of RPM to hit peak efficiency while delivering high battery charge rate to an AGM bank.

As far as I am aware, the only way to regulate is to speed up and slow down, which of course means the frequency will change radically as well. Not a problem if the AC is turned into DC and tightly controlled say with PWM to charge the batteries.....

Andy what about adusting the field current while the speed is held constant. That is a kind of regulation also. Frequency is fixed but output varies .

You are missing/forgetting a significant fact, there is no rotor field or field current to adjust!! The rotor coil (and brushes) has been removed and replaced with a permanent magnet setup!!!

I also like the terminology too, they call the output "Wild AC" in part 3 that they also mention, CANNOT be used to drive AC things!!!

Here is how its done:-

Part #1

http://www.youtube.com/watch?v=eX166iDh8Fs

Part #2

http://www.youtube.com/watch?v=ebYGTVW9z_k&feature=related

Part #3 AC conversion

http://www.youtube.com/watch?v=lBbC09nVs5o&feature=PlayList&p=4EC4798056FEBF4E&playnext=1&playnext_from=PL&index=1

On a windmill with a PMA alternator, you really need to control the speed of the blades to control the output, a mechanical nightmare for many DIY people....most just divert the excess power into some sort of resistor....

Now if the resistor was a water heater, maybe some water could be boiled to make proper usage of the power......

Elnav,

Why not just get a 3 stage charger, to top off the batteries properly ? Perhaps a IOTA 12 VOLT 55 AMP and 24 VOLT 25 and 40 AMP CHARGER. We don't market these but many others do.

Joe

That is what I ended up doing but it added to system complexicity and overall cost.

Yes we do have an readily available product to suit your requirements. The alternator will give you 53 volts out put at 50 amps and the effeciency is almost 75 %.

YES WE HAVE A RANGE OF 48V DC ALTERNATORS WHICH CAN GIVE YOU AN OUT PUT OF 15AMPS TO 45 AMPS AT 53 VOLTS , DEPENDING UPON THE SIZE OF ALTERNATOR.

email ID r_d@jumpsindia.com

Please do not post in caps in the future...

Will the real GUEST please stand up and reveal your true identity. How else can we see your website.

So now we have two 'guests ' one claiming a 53V alternator with 15 amps output and the other claiming a 15 - 45 amp output @ 53 volts. is this a case of two competitors who decline to reveal their true identities.

More details please?

If the email address @jumpsindia is in fact from a vendor located in India can you please provide details of shipping cost to other parts of the world. TIA.