Motors as Generators
DAC, it's been a while since I've played with small engines, but... isn't
there a small plastic or possibly tin/stamped steel "flapper" under the
flywheel cover? This was used on B & S engines as a crude limiter -
hooked to the carb. You could reverse the linkage and use it to increase
engine speed when the engine slows.
As for my idea on this thread, I have wanted to use one of my old
lawnmower engines to turn an automotive alternator connected to a
battery, to keep it charged when in use, so I could use a large enough
inverter to run important items during a power outage - in other words,
a homebuilt generator. Since the major items can be found relatively
cheap or free (you should see the number of newer lawn mowers thrown
in the trash around here, and useable alternators are almost giveaways at
the local junk yard!), with the exception of the inverter, this should be a
viable alternative.
Now to my question, what is needed to use an alternator in a standalone
situation such as this? Don't they need an initial energizing pulse to get
them operating? And then there is the charging circuit. Does anyone know
how this can be done or know of websites that have reliable information
on the circuits/wiring for such a setup?
Knowing how long my old B & S engine runs at full tilt on the quart or so
of gas in the little tank, I figure that running just faster than idle and using
a step-up pulley, it should run between 1-1/2 to 2 hours (probably
optimistic) on the same amount of fuel, all while spinning fast enough to
charge the old lead acid storage unit.
Final question. Is this "do-able" or is it just another Quixotic adventure?
CeaSaR
there a small plastic or possibly tin/stamped steel "flapper" under the
flywheel cover? This was used on B & S engines as a crude limiter -
hooked to the carb. You could reverse the linkage and use it to increase
engine speed when the engine slows.
As for my idea on this thread, I have wanted to use one of my old
lawnmower engines to turn an automotive alternator connected to a
battery, to keep it charged when in use, so I could use a large enough
inverter to run important items during a power outage - in other words,
a homebuilt generator. Since the major items can be found relatively
cheap or free (you should see the number of newer lawn mowers thrown
in the trash around here, and useable alternators are almost giveaways at
the local junk yard!), with the exception of the inverter, this should be a
viable alternative.
Now to my question, what is needed to use an alternator in a standalone
situation such as this? Don't they need an initial energizing pulse to get
them operating? And then there is the charging circuit. Does anyone know
how this can be done or know of websites that have reliable information
on the circuits/wiring for such a setup?
Knowing how long my old B & S engine runs at full tilt on the quart or so
of gas in the little tank, I figure that running just faster than idle and using
a step-up pulley, it should run between 1-1/2 to 2 hours (probably
optimistic) on the same amount of fuel, all while spinning fast enough to
charge the old lead acid storage unit.
Final question. Is this "do-able" or is it just another Quixotic adventure?
CeaSaR
Hey, what do I know?
-
Chris Smith
- Posts: 4325
- Joined: Tue Dec 04, 2001 1:01 am
- Location: Bieber Ca.
A lot of the newer Alternators are simply a one wire set up.
My 4x4 used a second battery and alternator with one wire, a intermittent solenoid and warning chime joining the two batteries in case of accidents.
No energizer or indicator wires were used.
On the older types simply add in a tiny bulb or resistor into the indicator circuit which is ignition controlled, sending the starting pulse [field] to energize the alternator.
With the motor off [key on] the sense feed will be positive and when the alternator starts spinning its sense wire also becomes positive shutting off the bulb and circuit.
My 4x4 used a second battery and alternator with one wire, a intermittent solenoid and warning chime joining the two batteries in case of accidents.
No energizer or indicator wires were used.
On the older types simply add in a tiny bulb or resistor into the indicator circuit which is ignition controlled, sending the starting pulse [field] to energize the alternator.
With the motor off [key on] the sense feed will be positive and when the alternator starts spinning its sense wire also becomes positive shutting off the bulb and circuit.
ChrRyb, I'm sure its possible since you are just duplicating what is in a car but on a smaller scale. You may need a car battery and regulator to complete the project BOM. For a wiring diagram, just take what you need from any Automotive wiring diagram with sufficient detail and the same type of alternator.
As for practicality, if your Inverter were too powerful, you may be tempted to connect a load that might stall the engine (i.e. large load makes inverter demand more current from alternator which in turn transmits more torque resistance to the engine making it work harder.) Not sure where that practical limit would be though. A rough HP to watts conversion derated by the efficiency of the inverter would place the ballpark. (6HPx746W/HP)*80% makes for about 3500W or about 30A at 120V. Seems like too much, Maybe the efficiency is not that good or the alternator would be a bottleneck
Frankly, If i wanted to make temporary power that way, I would simply upgrade the alternator in my PU truck to the biggest I could find and mount a honkin inverter under the seat and toss in an extension cord to hook in. 2 hours idling in the driveway might not use much more gas than the mower and would be a heck of a lot quieter and cleaner. Portable yes, but not in the same way. Besides its not the first two hours of a blackout that count, its hours 4-12 when the house gets cold or the fridge starts to thaw
As for practicality, if your Inverter were too powerful, you may be tempted to connect a load that might stall the engine (i.e. large load makes inverter demand more current from alternator which in turn transmits more torque resistance to the engine making it work harder.) Not sure where that practical limit would be though. A rough HP to watts conversion derated by the efficiency of the inverter would place the ballpark. (6HPx746W/HP)*80% makes for about 3500W or about 30A at 120V. Seems like too much, Maybe the efficiency is not that good or the alternator would be a bottleneck
Frankly, If i wanted to make temporary power that way, I would simply upgrade the alternator in my PU truck to the biggest I could find and mount a honkin inverter under the seat and toss in an extension cord to hook in. 2 hours idling in the driveway might not use much more gas than the mower and would be a heck of a lot quieter and cleaner. Portable yes, but not in the same way. Besides its not the first two hours of a blackout that count, its hours 4-12 when the house gets cold or the fridge starts to thaw
haklesup,
I'd love to just use the standard vehicular hook up ("big honkin..."), but
seeing as I must park in a public lot, well, you see my reasoning.
The block diagram for the whole build would be:
Gas engine -> alternator -> charging circuit -> battery -> inverter
Basically, I would just be running the alternator to keep the battery
charged while in backup mode, not to supply all the power to run the
inverter.
To keep the battery up to snuff during regular times, a charger would be
connected once a week to top it off - sort of in the vein of the battery
charger switcher in the January issue...
As for the "times", we have had a few problems here with prolonged
periods sans power. Last summer we lost all the food in both the
refrigerator and the 2nd freezer when that really bad wind storm took out
a large portion of the power grid. Parts of our area were out for over 4
days. There were other times I wish we would have had some auxiliary
electric, but I digress... I have no problems with the short term outages.
It's during the longer stretches you mention that I would like to be able
to plug in the needed appliances (one at a time) for a "recharge" /
prevent further disaster.
CeaSaR
PS, I have updated my member name to reflect my signature. Now I truly
am "CeaSaR"!
I'd love to just use the standard vehicular hook up ("big honkin..."), but
seeing as I must park in a public lot, well, you see my reasoning.
The block diagram for the whole build would be:
Gas engine -> alternator -> charging circuit -> battery -> inverter
Basically, I would just be running the alternator to keep the battery
charged while in backup mode, not to supply all the power to run the
inverter.
To keep the battery up to snuff during regular times, a charger would be
connected once a week to top it off - sort of in the vein of the battery
charger switcher in the January issue...
As for the "times", we have had a few problems here with prolonged
periods sans power. Last summer we lost all the food in both the
refrigerator and the 2nd freezer when that really bad wind storm took out
a large portion of the power grid. Parts of our area were out for over 4
days. There were other times I wish we would have had some auxiliary
electric, but I digress... I have no problems with the short term outages.
It's during the longer stretches you mention that I would like to be able
to plug in the needed appliances (one at a time) for a "recharge" /
prevent further disaster.
CeaSaR
PS, I have updated my member name to reflect my signature. Now I truly
am "CeaSaR"!
Hey, what do I know?
If cheap, quiet AC is what you're after- buy a 1500 watt Honda generator for $150. (Aldi's had them a few months back)
Unless you want the project of building a frame, wiring up the alternator, regulator and battery. Maintaining the battery. Buying an inverter. Regulating the motor speed. Fun stuff.
Unless you want the project of building a frame, wiring up the alternator, regulator and battery. Maintaining the battery. Buying an inverter. Regulating the motor speed. Fun stuff.
So what you really want is a cordless battery charger.
jwax has a point. Both harborfreight.com and heartlandamerica.com have several models of inexpensive light duty generators.
http://www.heartlandamerica.com/browse/ ... 791AAB8EF1
Hmmm. 1000W generator for $129 or 1250W inverter for $99
Next time a summer blackout hits, rush to the store and buy 4-5 blocks of dry ice and pack the freezer. That can last almost a week if you keep the door closed. And it doesn't cost much (if you beat your neighbors to it)
jwax has a point. Both harborfreight.com and heartlandamerica.com have several models of inexpensive light duty generators.
http://www.heartlandamerica.com/browse/ ... 791AAB8EF1
Hmmm. 1000W generator for $129 or 1250W inverter for $99
Next time a summer blackout hits, rush to the store and buy 4-5 blocks of dry ice and pack the freezer. That can last almost a week if you keep the door closed. And it doesn't cost much (if you beat your neighbors to it)
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