power for using an alternator for battery charging?

[ron17571]

Hi, im new with sterling type engines. I would like to charge deep cycle battery's. So I see sterling small scale engines on ebay. Low RPM rare earth alternators from wind blue power, starts charging at 180 RPM. I figure put the two together, maybe using a some kind of jack shaft to change the gearing? Anyone here made such a thing? I have noticed the lack of mid size sterling engines, I would like to avoid making one from scratch, but do have some ideas.

[RonT]

I'd best let the more experienced and knowledgeable on this list answer this question. In the short time that I've been here the question about the availability of DIY, kit, or manufactured Stirling engines in the centiWatt to low kiloWatt range has been one of the most frequently asked by newcomers to the list.
Ron T (Yellowknife, NWT, Canada)

[Ian S C]

Ron T, you will need about 18 Volts at about 10 Watts for a 12 Volt battery, my larger motors produce about 2.5 to 3 Watts, and quite good for charging nicads, and smaller accumulators.
To get a suitable sized motor you might just have to build, or have built, a suitable sized motor. Your first problem is deciding which design of motor to build, then how!! Read as much as you can find. Ian S C

[theropod2]

Ron T, you will need about 18 Volts at about 10 Watts for a 12 Volt battery, my larger motors produce about 2.5 to 3 Watts, and quite good for charging nicads, and smaller accumulators.
To get a suitable sized motor you might just have to build, or have built, a suitable sized motor. Your first problem is deciding which design of motor to build, then how!! Read as much as you can find. Ian S C

There is another way to use low amperage high voltage sources to charge low voltage batteries. It's complicated.

A large capacitor bank, independent of the battery bank, is charged at a higher voltage than the battery bank. At a "trigger" voltage a gate is opened and a very short pulse of power is sent to the batteries. When the cap bank voltage drops, which it does very fast, the gate is closed and the cycle repeats. This is not a good thing to use when other electronic devices, like inverters, are also reading the battery voltage. That sudden spike will trip many inverters, or worse. It does work for less sensitive loads like lights, pumps and such. I've made stepper motor wind turbines that wanted to make around 36 volts when spinning good unloaded. Directly connected to the battery they went into stall. I made a near 1 farad bank of 50volt caps. A simple 555 timer, protected by a regulator, pulsed the cap bank bank at a given interval unless a zenner diode breakdown voltage was reached by the cap bank and then the mosFET would fire until the high voltage cap bank condition passed no matter what the 555 said. I rigged up a tiny little green LED to tell me when the pulses were firing, and when the tiny little wind turbine went into direct charge mode.

R

[Ian S C]

You are more likely to have a low voltage, and low current, low voltage can be boosted, but that drops the current by the same proportion, you can still charge batteries, just takes longer.
For your alternator, ceramic magnets are possibly better, rare earth magnets will cause cogging, loading the motor, you want an alternator that run freely, the main advantage of the axial alternator is that you can adjust the armature to stator gap.
Don't even think of an automotive alternator, they are not very efficient, the one I have on a 1 hp 2 stroke petrol/gas engine will produce about 200 watts. Ian S C

[theropod2]

You are more likely to have a low voltage, and low current, low voltage can be boosted, but that drops the current by the same proportion, you can still charge batteries, just takes longer.
For your alternator, ceramic magnets are possibly better, rare earth magnets will cause cogging, loading the motor, you want an alternator that run freely, the main advantage of the axial alternator is that you can adjust the armature to stator gap.
Don't even think of an automotive alternator, they are not very efficient, the one I have on a 1 hp 2 stroke petrol/gas engine will produce about 200 watts. Ian S C

An axial flux alternator has no ferrous metal in the coils/stator so there is no gogging. There might be some eddie current heating if the stator is not designed right, like having magnet wire too large.

R

[fullofhotair]

This would only be for lighting. So you want to use an axial flux alternator. The little bit of reading I have done recommends using a 3 phase alternator and a3 phase rectifier? It said for low rpms so 350 to 500 rpm is ok? To get the most light ,would I use LED or fluorescenct? Dc or AC? Anything else that might be helpful?

[theropod2]

This would only be for lighting. So you want to use an axial flux alternator. The little bit of reading I have done recommends using a 3 phase alternator and a3 phase rectifier? It said for low rpms so 350 to 500 rpm is ok? To get the most light ,would I use LED or fluorescenct? Dc or AC? Anything else that might be helpful?

It would be possible to use the raw ac directly for lighting sans rectifiers. Each phase would be able to power a little incandescent lamp.

R

[fullofhotair]

theropod2,
Arent LEDs more efficient? Iam trying to get as much light as possible. A little circuitry and super cap are ok. You have probably seen the U-tube videos where they use an earth battery=1volt to light up a string of LEDs. They use a joule thief and capacitor. Can I use the axil alternator to do the same thing? How should the alternator be wired, 3 phase or altogether ? Do I need a 555 or anything else?

[theropod2]

theropod2,
Arent LEDs more efficient? Iam trying to get as much light as possible. A little circuitry and super cap are ok. You have probably seen the U-tube videos where they use an earth battery=1volt to light up a string of LEDs. They use a joule thief and capacitor. Can I use the axil alternator to do the same thing? How should the alternator be wired, 3 phase or altogether ? Do I need a 555 or anything else?

Gimmie a day or so to look through my files, as I did save the schematic somewhere.

3 phase is standard in most such alternators, but I've seen 5 and 9 phase designs. I've also seen each coil in the stator rectified individually, the rectifiers wired in series and all sorts of arrangements.

RS

[ron17571]

Well thanks for the replies. I get the feeling that sterling motor just don't have much power. I guess I could see one powering a small fan. For battery bank charging I first liked the idea of an low RPM lister diesel,but the fuel required is a turn off. Than I have considered a steam engine(and still do) The sterling motor seems like it would make better use of wood. I'm guessing I would need to build one large enough. I would need to study it more. I'm thinking the mass of whatever is used as a piston is kept light and doesn't work well to drive a pulley. That's why I mentioned a jack shaft to alter gearing.
A modified off road shock with the heat dissipating aluminum fins came to mind. Or a large tube of steel on the hot side attached to an aluminum pipe on the end with some aluminum fins or a small cooler for a computer.. A chain saw engines crank and cylinder piston combo is a thought. Even parts on ebay for Chinese ATV engines, small four stroke engine parts are cheap. 50 cc rod crank and cylinder, pistons would be cheap.
It just doesn't seem like it would be much to spin a alternator a few hundred RPM. If only its as easy as I'm thinking? HaHa.

[Hawke]

I have dabbled in Steam Engines some and can tell you the power output per same size piston on a Stirling is quite different. They do require more solid sealing and stronger materials. At the very least is soldering joints even in model prototypes. Even in models, you will want a brass boiler and cant use things like graphite pistons. Weight is not an issue like in Stirlings. A copper pipe 1/2 ID piston cylinder Steamer for example run on the same heat as given to model Stirlings would produce more than enough to turn your alternator for trickle deep cycle battery charging. Steam is quite powerful. Safety, the danger of boilers blowing up was the inspiration for the development of Stirlings. Hands down they are quite the powerhouses compared to Stirlings.

[Ian S C]

One thing against steam is the boiler, its large, hot and messy, you will need to get it tested each year for insurance depending on which part of the world you live in.
The Stuart Turner S9 steam engine that I rebuilt for a friend earlier in the year produced on an alternator about 10 watts at 70 volts, on around 60 psi of air(have not tried steam), it has a bore and stroke of 1 1/2", and is double acting.
Hawke, don't use brass for a boiler, it is best to build small boilers from copper. With brass the zinc leaches out leaving the boiler porus, It does to a certain extent depend on the impurities in the water, but also a certain amount of electrolytic effect, the boiler inspector(who you must see during the build) will tell you which materials are accepted, and what grade of silver solder to use. Ian S C

[Hawke]

I stand corrected on the boiler Sir Ian. Thank you. I guess Im in my "toy model" frame of mind again, LOL. Here's a picture of my little PM Research Steam engine with a brass boiler I got for it. Havent run my PM Steamer on anything but compressed air yet. These "models" can be done with a tin can boiler even but I ALWAYS have a release valve in place on the boiler.


Here's a video of a tin can boiler and a PM2 engine. Steam release is extreme in this example however you can see the pressure that steam has done to the tin can. Its probably only seen slightly over 10 - 15 PSI too! There's a glimpse of the power steam can have.
https://www.youtube.com/watch?v=8ogDZIskb-Y

[Hawke]

Yep, missed the PSI Gauge at start of video, 15lbs. His spring and shaft is loose on the oscillating piston there which is releasing all that steam.

Supporting Ian caution on boiler dangers, here's a small scale explosion:
http://www.youtube.com/watch?v=0R348vGkjyw