Build generator using engine + alternator.

[Doodlebug]

Starting a new topic for the purpose of people searching the forum.

 

As you may know our generator has packed up due to an electrical issue and it is not financially valid to fix the generator.

 

I have however found that I can take everything off the engine and it still runs (though Im going to need to play around with the carbs to get the thing running smoothly.

 

What I would like to do is take the yamaha engine (which runs at 1.61 kW / 6,500 rpm) and connect an alternator in order to directly charge the batteries.

 

I am assuming this will work well - its a good little engine and pretty efficient and quiet.

 

How do I go about finding the right alternator? I was hoping for about 50-100amps which should work fine with the engine. At about 1.2kw.

 

So how do I go about finding an alternator. Will any one do? I was assuming I need to find (for instance) a 60 amp alternator at 6000rpm but that would leave the generator at a high revs.

 

So do I just get a large alternator and assume its going to work or is there more too it?

 

Also can I mount them in a line. I.e. the alternator directly attached or does it need a pully system? I'm wondering about balance and vibration.

 

Thanks

 

Doodlebug

[Paul's Nulife4-2]

Rather than mess about with your outboard eng, and if a cheap Generator isn't desirable, Then consider a very cheap old Flymo petrol engine, Take the blade off, and fit a double pulley, Then you can have Two Alternators fitted in a

Alt--Flymo--Alt

Configuration, this should give oodles of pwr, and you can regulate the speed of the engine via the throttle.

[Doodlebug]

Rather than mess about with your outboard eng, and if a cheap Generator isn't desirable, Then consider a very cheap old Flymo petrol engine, Take the blade off, and fit a double pulley, Then you can have Two Alternators fitted in a

Alt--Flymo--Alt

Configuration, this should give oodles of pwr, and you can regulate the speed of the engine via the throttle.

 

Its not the outboard engine its the engine out of the generator which had seized due to an electrical fault. With the windings removed it runs fine.

 

So i'm basically doing which you suggest but don't know what alternator to use or how best to mount them

 

Cheers.

[John V]

I don't know the generator type that has gone bang but from the sounds of the revs I would guess that it is one of the new style inverter types, I would suggest you are heading down a long, painful and probably disappointing route. From the sight I have had of one of that type there 'aint much to connect to. If it is one of the more conventional type generators, they normally run at a nominal 3,000 rpm but often the alternator front bearing provides one of the crank bearings for the engine which complicates things, Paul's suggestion is probably best ....get a small free standing engine with a shaft output and put a couple of pulleys on it.

[Doodlebug]

I don't know the generator type that has gone bang but from the sounds of the revs I would guess that it is one of the new style inverter types, I would suggest you are heading down a long, painful and probably disappointing route. From the sight I have had of one of that type there 'aint much to connect to. If it is one of the more conventional type generators, they normally run at a nominal 3,000 rpm but often the alternator front bearing provides one of the crank bearings for the engine which complicates things, Paul's suggestion is probably best ....get a small free standing engine with a shaft output and put a couple of pulleys on it.

 

Not sure I fully understand - can upload some pictures? But from the way it looks there is a stepper motor which controls the speed of the engine. A screwdriver is currently replacing that and as I twist it the revs increase so I can set this to an optimum rate.

 

The flywheel and magnets for power generation are simply bolted on with an m12 nut.

 

Assuming I get the motor working fine by itself I figure its just a case of joining the two. 3000rpm sounds about right. It revs up to 6500 but thats far louder and noisier than when idling. All I need to do is make sure I buy thr right alternator.

 

Have I misunderstood though?

[John V]

Your engine is obviously from one of the inverter type generators, the alternator does not produce 240v 50Hz directly instead it produces a voltage that is turned into DC then put through an inverter to give 240v 50Hz.

Unless you are a very skilled and talented machinist I would suggest you would find it difficult/impossible to fit an alternator in line with the crank. If the engine was like the one I examined a bit ago there was not much room to try and fit a pulley either. I also find it very hard to throw out a perfectly good item that "just needs to have something like that fitted to...." Unfortunately much bitter experience and a vast collection of "things that might come in useful one day" have shown me the error of my ways.

[Doodlebug]

Your engine is obviously from one of the inverter type generators, the alternator does not produce 240v 50Hz directly instead it produces a voltage that is turned into DC then put through an inverter to give 240v 50Hz.

Unless you are a very skilled and talented machinist I would suggest you would find it difficult/impossible to fit an alternator in line with the crank. If the engine was like the one I examined a bit ago there was not much room to try and fit a pulley either. I also find it very hard to throw out a perfectly good item that "just needs to have something like that fitted to...." Unfortunately much bitter experience and a vast collection of "things that might come in useful one day" have shown me the error of my ways.

 

Yes it is, I would take off the magnets and remove it from the case in order to make space.

 

I was going to get a flexible coupler and a used alternator from ebay to test out the idea I think. Must be possible because whoever sells those super chargers seems to be doing the same thing then selling them for £500.

[George94]

The challenge here is to find a way to attach a pulley to the motor. If you can do that then you can drive a small car alternator, which will charge your batteries.

 

As it is a 1000 Watt machine, it should theoretically be capable of driving a 70 amp alternator (70*14 = 998 Watts).

 

So you'd probably be fine with a 50 Amp 12 Volt alternator as long as it turns at the right rpm. And you can adjust RPM by playing with different pulleys.

 

We know you can do it, Doodle.

[John V]

Good luck !!! (not sarcasm) even if it's not successful I hope you have fun doing it cheers John

[bizzard]

If the engine has a bit of crankshaft stub sticking out from either end, it's quite simple to couple the alternator minus it's pulley directly to it nose to nose with a bit of flexible hose and a couple of hose clips. Only pick an alternator that's well within the capacity of the engine. The whole ensemble could be mounted on a Dexion frame.

[John V]

that's fairly high revs he was talking about Bizz

[ditchcrawler]

Biggles blogged over several postings, you should be able to track them from here http://boatbuildblog.blogspot.co.uk/2013/11/generator-project-new-blog.html

[Doodlebug]

If the engine has a bit of crankshaft stub sticking out from either end, it's quite simple to couple the alternator minus it's pulley directly to it nose to nose with a bit of flexible hose and a couple of hose clips. Only pick an alternator that's well within the capacity of the engine. The whole ensemble could be mounted on a Dexion frame.

 

This is the bit I dont understand.

 

Alternators are not listed by their RPM, Horsepower etc they are listed by the car they are made for.

 

I have found loads of them but none of them tell me any specification. Take this one for instance:

 

http://www.ebay.co.uk/itm/MAZDA-2-2006-2nd-GENERATION-1-25L-ALTERNATOR-70-AMP-2S6T10300CB-/171252052767?pt=LH_DefaultDomain_3&hash=item27df6af31f

 

Is it going to work and how do I know it is regulated (although most are nowdays?)

 

This is how I would connect the two.

 

http://www.ebay.co.uk/itm/5X6-5X8-6X8-8X12-10X12mm-CNC-Motor-Shaft-Coupler-Flexible-Couplings-OD-26x35mm-/391115405819?pt=LH_DefaultDomain_3&var=&hash=item5b104b79fb

[bizzard]

that's fairly high revs he was talking about Bizz

With a big alternator and a flat battery I doubt if it'd rev to anywhere near 6,500 rpm. 4,000 revs would be ok.

[John V]

most automobile alternators have a maximum RPM of either 8 or 9,000 RPM but can produce full power from a lot less.

 

we crossed posts there I think......still reckon thats a lot of revs through a bit of tube and jubilee clips

Edited June 25, 2015 by John V

[bizzard]

most automobile alternators have a maximum RPM of either 8 or 9,000 RPM but can produce full power from a lot less.

 

we crossed posts there I think......still reckon thats a lot of revs through a bit of tube and jubilee clips

Quite so most modern cars can run them up to around 6000 revs or more. Connecting an alternator or dynamo nose to nose with an engine was very popular years ago, but with torquey old Briggs and Stratton lawn mower engines.

[Doodlebug]

These three have specifications which help.

 

http://www.balmar.net/pdf/six-series-alternators.pdf

http://delcoremy.com/Alternator-Models/24SI-Heavy-Duty-Alternator.aspx

https://j109.org/docs/balmar_110a_alternator_model_70-110_manual_7-series.pdf

 

They all look pretty useless below 2000rpm. I assume a generator will always be running this fast (though that does seem pretty fast doesn't it? Will it need gearing up?

 

Thanks for the help its appreciated.

[Richard10002]

I usually find that trying to reinvent the wheel costs more in the long run, and doesnt work as well... unless you are extremely handy, and of the inventor type.

 

You can buy a Kipor 1kw generator for just under £400... that's what I would do.

[DHutch]

You will also then need something to regulate engine speed, as unlikely older electro-mechanical gennys as you have found out most inverter based ones seem to have an electronic throttle as well.

 

 

Daniel

[Taslim]

You will also then need something to regulate engine speed, as unlikely older electro-mechanical gennys as you have found out most inverter based ones seem to have an electronic throttle as well.

 

 

Daniel

I see where you'r comming from but it's an automotive alternator so should deal with varing engine RPM as the load changes as long as the engine is self regulating against load changes or has a manual throtle. You'd get 12v more or less. If the OP was off to do 220V @ 50Htz it would be a different tin of beans.

 

Doodlebug. That beautiful, ellegant, coupling you fancy won't cut the mustard. Great for constant load, they don't do torque. Listen to that nice Mr Bizzard. I used compresor hose & two stainless Jubilee clips.Been OK for 20 years. (lawnmower engine is getting weary though).

 

Dexion? Do they still make that?

[bizzard]

I see where you'r comming from but it's an automotive alternator so should deal with varing engine RPM as the load changes as long as the engine is self regulating against load changes or has a manual throtle. You'd get 12v more or less. If the OP was off to do 220V @ 50Htz it would be a different tin of beans.

 

Doodlebug. That beautiful, ellegant, coupling you fancy won't cut the mustard. Great for constant load, they don't do torque. Listen to that nice Mr Bizzard. I used compresor hose & two stainless Jubilee clips.Been OK for 20 years. (lawnmower engine is getting weary though).

 

Dexion? Do they still make that?

I don't think Dexion is made anymore. A few bits of say inch angle and a drill should do it. It's best to leave the keys in the shafts for the hose to grip on or super glue the hose as well as the clips to prevent any slippage.

[DHutch]

I see where you'r comming from but it's an automotive alternator so should deal with varing engine RPM as the load changes as long as the engine is self regulating against load changes or has a manual throtle. You'd get 12v more or less. If the OP was off to do 220V @ 50Htz it would be a different tin of beans.

 

Oh yeah, I am not saying it has to be posh and maintain 50hz accurately, but you will need something to stop it over speeding horribly the first time the load drops off surely...

[Neil Smith]

Mine was also an old Genny but a slower reving Honda, just put a 5" pulley on shaft then mounted an alternator with 2" pulley to gear it up, as yours revs to 6500 rpm you could connect directly but make sure you get one thats rotation is the same as your engine.

 

Neil.

Mine was also an old Genny but a slower reving Honda, just put a 5" pulley on shaft then mounted an alternator with 2" pulley to gear it up, as yours revs to 6500 rpm you could connect directly but make sure you get one thats rotation is the same as your engine.

 

Neil.

[ditchcrawler]

I don't think Dexion is made anymore. A few bits of say inch angle and a drill should do it. It's best to leave the keys in the shafts for the hose to grip on or super glue the hose as well as the clips to prevent any slippage.

http://www.dexionstore.co.uk/

[smileypete]

Typically an inverter genny would have a three phase stator:

 

 

Could be interesting to find out (safely!) what the output voltage is across each winding over the rev range of the engine, it MIGHT be possible to rectify the three phase and use it to power a charger.

 

cheers, Pete.

~smpt~

Edited June 26, 2015 by smileypete