Voltage Regulation

[robbstech]

Hi all,

I'm new here and I am in the middle of building a generator and I am wanting to know how I can limit the voltage output of the alternator to 12-15 volts so it can be fed directly into the inverter so I can invert it to 230v ac?

The alternator is simmilar to the ones used in the 10' diameter wind turbines in otherpower.com

I am using a small 5 horsepower stationary engine to run the alternator but I need to know how to limit the voltage so it doesnt blow the inverter which has a maximum input voltage of 15 volts.

I was also thinking of putting a 40Ah battery with the generator aswel so the generator only has to run when the battery levels gets low. Is it possible to run the output from the alternator in parallel with the battery and then into the inverter? Will this keep a constant voltage of 12 volts?

Thanks

Rob

[SparWeb]

Hi, welcome aboard,

...it possible to run the output from the alternator in parallel with the battery and then into the inverter?

This is actually the normal way of operating an inverter.  They work poorly when the voltage is allowed to fluctuate, and most require a sufficiently large battery to keep the input voltage in the 12v range.  The ones I've used allow voltage as low as 10v and as high as 15v, beyond which they cut out to protect themselves.

Depending on what you have in mind for generator (stationary engine, wind-powered, hydro) you will have different amounts of power to work collect, store and use, with different reliability.  Since you are building the 10' windmill, then storing the power it produces either means a bank of batteries or electric heat (hot water).  There are other ways of storing electric energy, but you should tell us more about what you want to do.

[robbstech]

All i want to do is run the inverter straight from the alternator but use the battery to keep the voltage a constand 12 volts.

Will I still need some sort of charging regulator even tho power will only be drawn when the engine is running so the battery will probably never get fully charged?

Thanks

Rob

[electronbaby]

are you attempting to store your energy in batteries? or are you attempting to feed it into the grid? Each method is different, and therefore requires different types of equipment. Please give us more details...

[robbstech]

I am not wanting to store the electricity at all, I just want to run it straight into the inverter because the alternator will be spun by an engine!

I just need to know how to keep the voltage a constant 12-15 volts?

Cheers

Rob

[ghurd]

You will need some kind of 'controller' to keep the battery within specs.

A 40AH SLA battery will not appreciate 80A, either going in or out.

A larger battery will help, and a larger flooded battery would be a better choice.

Will need to balance the input with the output.  Not a simple task.

Really, is not a good plan from the inception.

It could be done, but it would be expensive, very complex, and certainly horribly inefficient.

Best way I can see to do it is with a big battery.  

We don't have enough information to go on.

G-

[robbstech]

wht if i put 2 40ah batteries in parrallel?

Cheers

Rob

[ghurd]

Getting a tiny bit better.

The margin of error is now half of infinity.

Falling back to the stand-by analogy,

How long is a piece of string?

Are 2 pieces of string long enough?

[electronbaby]

You will most likely need to have batteries to act as a "buffer". I do the same thing you are doing, and since I am off grid, I must use batteries to connect my inverters. The alternator output is then fed (at a higher voltage than the battery bank) through an MPPT controller to the batteries. If you do not use batteries, then you will have a heck of a time regulating the engine speed to within the inverter voltage input window. If you really wanted the highest efficiency, you would skip the inverter altogether, and wind your alternator for 110v output. See, you still have the problem of regulating engine speed. Things would be much easier if you were trying to feed into the grid since the grid tie inverter would do the power point tracking altogether and you would have a wide engine speed window without needing to worry about battery storage. But then you would have no back-up capabilities.

Batteries are not expensive, not sure what your scared about???

It seems to me if you were concerned about efficiency, you would not be going with a 12v system anyway???

How do you plan on regulating engine speed without batteries???

[robbstech]

right testes my alternator today, i hooked it up to a car bulb with a volt meter and ammeter, i was able to light the bulb turning the alternator by hand and i was getting 13 volts and 5 amps at about 70-80 rpm (guess).

I plugged a lamp into my inverter and tested it on a battery with the ameter and it was drawing 1.5 amps out of the battery to light this lamp.

I then connected the inverter to the alternator and spun again at around 70-80 rpm and the inverter switched on but the bulb would not light! I know the alternator can provide enough current to light the lamp but it wouldn't light!

Any suggestions?

Cheers

[electronbaby]

you might be buying a new inverter soon :-)

[robbstech]

But this inverter still works!

[ghurd]

"by hand and i was getting 13 volts and 5 amps".

At the same time?

That would be 65W, which is about what the bicycle generators can sustain for a while.

See how many amps you can get into a battery by hand.

Open volts or shorted amps does not mean a whole lot.

The volts will vary wildly depending on the load amps.  If the load is reduced, the voltage increases.  And if the load is reduced, the motor speed increases, increasing the voltage even more.

If a high wattage bulb burns out, I expect the inverter will receive enough volts to blow it up.

Now you are experiencing why it needs a battery.

Have a look and think about this video.  A car battery can not keep this alternator voltage within inverter requirements for 10 seconds.

http://s298.photobucket.com/albums/mm249/Southbuck7/?action=view&current=Movie.flv

Suggest you get a reasonable sized battery,

before you need a reasonable sized battery AND a new inverter.

G-

[robbstech]

right got'ya, got'ya, got'ya!

I guess i just need to experiment a bit then

Thanks for all the replies guys!