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Last edited by almac; 03-14-2016, 05:43 PM. -
Probably something around 2000 RPM at full throttle.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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thanks, i will try a 2:1 pulley ratio for starters, the battery load might drag the rpm down to 1000 at full throttleComment
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That may not do what you want. Imagine a case with a PWM controller. When the battery is low you'll open the throttle wide to get a decent amount of power to the battery. Then the battery will charge. At some point the switch will open. The motor will then become completely unloaded and will overspeed.
With an MPPT controller you have another problem. Most MPPT controllers are expecting a solar panel - and their V/I curves are dependent only on insolation, and the open circuit voltage doesn't change much with time. With a generator, as soon as you reduce its load, the RPM will increase over the course of several seconds, and the MPPT controller will have to react to that. MPPT controllers may not be able to anticipate a rapidly rising RPM, and you'll see the same problem.
(You'll see the same problem eventually no matter what you do; the controller will effectively "open" and the motor will overspeed.)
Because as long as the motor is running and providing power it will transfer power to the generator. So your system would work like this:explain why the motor wont need a diode to stop the batteries feeding back jflorey2
1) Motor is off. Generator switch is off. Nothing is moving.
2) You open the throttle on the motor. Still nothing happens; motor hasn't started yet.
3) You close the switch. If it is really a commutated motor, then it starts running at its base speed. The motor spins as well and starts producing power.
4) You run the motor as long as you like.
5) When you are done you close the throttle (actually a fuel cutoff or ignition kill works better here.)
6) You open the switch. Both motor and generator stop. No power flows anywhere.
If you add a diode, you've just added .5 volts of loss and removed the option of using the generator to start the motor.
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im thinking the PWM charge controller would be a starter. the current doesnt just disconnect with PWM it gradually reduces. an over speeding 2 stroke lawnmower i can live with ,its not as though i wont hear it over speeding. at least the batteries wont cop an over voltage. i can set the RPM range of the 2 stroke engine to stay within the PWM controllers input voltageComment
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One more time. Use a dump load controller. If you set it up to cut over to the dump load if the lawn mower stops or if the battery voltage hits the bulk charge target, then you don't need a diode, and you don't need to stand there to turn everything off in the right sequence.CS6P-260P/SE3000 - http://tiny.cc/ed5ozxComment
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thanks, now i have to work out how many watts the DC motor can put out. the spec plate says 220Vdc 6.5A 2HP , could it put out 1400W ? something like this?
Last edited by almac; 03-16-2016, 12:43 AM.Comment
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You're mixing two different terms and coming to the wrong conclusion IMO.
PWM controllers "just disconnect." That's how they work. The term "pulse width modulation" means that an internal switch turns on and off, and the width of the on-pulse is changed (hence the name) to control how much power, ON AVERAGE, the battery gets. But at any given time it's off or on; it is only over the course of several minutes that it averages to a lower current.
Also, as batteries reach full charge they gradually take less current. So even if you have a PWM controller, and the switch inside is closed, the battery will take less current. That's not a function of the controller, it's a function of the battery.
Well, if you can afford the consequences of that, go for it and see what happens. You'll certainly learn a lot doing it.an over speeding 2 stroke lawnmower i can live with ,its not as though i wont hear it over speeding.
(BTW Sensi's idea is a good one; a dump load controller makes a lot more sense than a series PWM controller, and will not result in overspeed as the battery reaches full charge. Make sure to size the dump load larger than the maximum output of the generator.)
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I have owned a victa 2 stroke mowers for over 30 years, and spent 4 years as a mechanic at a Victa dealership. My current one is over 15years old. They are a simple robust engine. There has only really been one major change to them which was in the early 80s? They change the engine and carb design. The later carb is a bit of a pain.
Basically:
This engine will run up to 5000 rpm if you want, standard operating would be around the 3600rpm as with most stationary engines.
They are air governed and the way the carb throttle system operates makes small/acurate RPM adjustments hard.
The governor will be slow to react to engine load compared to mechanical governing that is in most engines.
They are noisy and use a lot of fuel compared to a 4 stroke.
If you do use it you will need to leave the cutter disc on, it acts as a flywheel.Comment
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hi bala, thanks for the info, RPM at 3600 is too high for the treadmill motor, i would be aiming for about 500 RPM to get around 32Vdc. will see more lawnmowers on the kerb around here so should find a 4 stroke , even if i dont the local markets have 4 stroke mowers for around $50Comment
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As I recall a treadmill motor is as much a brake as it is a generator. I doubt they are designed for continuous duty, much less continuous duty as a generator. I have seen many used in wind generator designs, but I wonder how they are doing a year or 2 later. If you get your idle governed, I think it could work, but you are going to want a Hydro/wind Charge controller, so as not to damage your batteries. If you get a year out of it would be amazing.4X Suniva 250 watt, 8X t-105, OB Fx80, dc4812vrfComment
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Most domestic 4st mowers will be about 3.5hp @ 3600rpm. They will have almost no hp at 500rpm.Comment
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