12v DC generator

[Fixit]

This year me and my buds want to be able to charge radios etc overnight and run the frezer.
rather than running the generator all night, were going to use an inverter wired to a battery bank (5x deep cycles)

now you could use the 12v dc outlet on most generators to charge the bank, but thats usually only 2-5A depending on the generator...
the other option would be to use a 50A automotive battery charger plugged into the generator (but those are expensive)
so heres my solution:
A lawnmower engine and an alternator!
- 5hp motor was $20 off craigslist
- 80A alternator was laying around (freebie)
- I still need to buy a 4-5" drive pulley for the motor ($30 from princess auto)
- V belt. $10?

the motor doesnt run yet, so I did a test run with my dewalt drill and im getting 14.5v at 2000rpm alternator speed.
should charge the battery bank at around 50-80A i hope!!!
http://im1.shutterfly.com/media/47a1d735b3127ccefe49adf74d5e00000030O02QZs2Lls0ZA9 vPg4/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/
test fit of the big parts

http://im1.shutterfly.com/media/47a1d735b3127ccefe48cb3c6dea00000030O02QZs2Lls0ZA9 vPg4/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/
wiring up the dummy light, feild wire and voltage sense wire

http://im1.shutterfly.com/media/47a1d735b3127ccefe49f7984d1c00000030O02QZs2Lls0ZA9 vPg4/cC/f%3D0/ps%3D50/r%3D0/rx%3D550/ry%3D400/
14.5V spinning it with the drill!

an interesting note that i learned is that these lawnmower engines wont run without the blade attached (so im told) they need the mass of the blade to act as a flywheel. right now my motor just backfires through the carb and rips the pull cord out of my hand without it.

[f350ps]

Why don't you just run the generator during the day with the freezer plugged in then shut it off at night? K

[Goliath]

You've obviously given this some thought, but here's my experience...

Batteries are heavy. Leave them at home and just bring gas.

Fill the tank...and run the generator & freezer only during the daytime (or if it gets warm).

[Phil]

I've got one for sale like that if you know any one who wants it. It has a horizontal 2 1/2 horse briggs and a 60 amp alternator. The exhaust runs through a water jacket to make it nice and quiet. It sounds a bit like a 2 1/2 horse bong.

[Fixit]

the other consideration is that i want to charge my handheld radios at night (12hrs if totally dead) they draw next to nothing so an inverter makes sense rather than running a generator
plus i dont have a generator so instead i spent 60 bucks and made this

also the freezer draws 2.5A running (300W)
my energy demands are 500W max (freezer, charger, and a light or two) but i need the power available 24hrs a day (freezer/day, radios/night) it makes more sense to me to use an inverter rather than a generator 24/7
maybe ill just run it during the day time (charge batteries up and run the freezer) and then shut it down at night for a quiet sleep

[Gun Dog]

an interesting note that i learned is that these lawnmower engines wont run without the blade attached (so im told) they need the mass of the blade to act as a flywheel. right now my motor just backfires through the carb and rips the pull cord out of my hand without it.I learned that the same way. I had the blade off and wanted to warm it up for an oil change. Ouch.

I think you're going to boil off the batteries or end up with a really slow charger. Generator engines have a governor to control the throttle based on load. The generator output will be too high without a regulator and a normal regulator is set up to slow/trickle charge the batteries. Good chargers (or smart chargers) have several charging modes. If the battery is low then a bulk charge (high current) is used to bring the battery to 70%. Then an acceptance charge (slower, lower current) takes the battery to %95. Then a float charge takes the battery to 100% and can be left charging without problems. You might be able to use a solar panel controller since they operate with a wide input voltage but one for 50A isn't cheap either.

[Fixit]

yes and no... it depends on the type of generator, perminant magnet or feild windings, and a DC generator is different than an alternator.... in a nutshel, the alternator is self regulating. it controls the current to the field windings to control voltage. the output in amps is depedant on alternator RPM (which is usually 2-3x engine rpm) they usually start putting out around 1500 alternator rpm and start to taper off around 5000rpm (think 60% output at engine idle and full capacity from 2000rpm+) essentially an alternator is a smart charger.
http://pirate4x4.com/tech/billavista/Wiring/Part2/images/10si%20perf%20curves_400.jpg

voltage should remain at 14.2volts until a load is applied.
a battery will only boil if its fed too high a voltage

for those who want to learn more than you wanted to know, heres a great article
http://pirate4x4.com/tech/billavista/Wiring/Part2/

[spreerider]

amps drawn is dependant on the load not the source, the alternator keeps a constant voltage due to its regulator circuit, and if the RPM drops the voltage will stay the same untill its too low.

batteries can boil from too much amps fed into them thats why you have a charger with a circuit that can lower the amps delivered as the battery gets closer to charged, and why most battery chargers have maintenance mode and charge mode, so you can trickle charge the battery or quick charge it.

most common reason for a battery to boil is you hooked it up backwards, sounds funny but i have seen it happen a few times when people are in a rush and not being carefull.

[bc mike]

I admire your creativity. I am sure you checked your freezer for a start up surge. They cycle alot. Consider the cost to lost food, stress and hunting time if your system fails. Then the cost of a small gas genny is small. I have an inverter generator. It works well. Very quiet and efficient. My last generator lasted 20 years and I hope the same for this. Good luck.

[Gun Dog]

amps drawn is dependant on the load not the source, the alternator keeps a constant voltage due to its regulator circuit, and if the RPM drops the voltage will stay the same untill its too low.

batteries can boil from too much amps fed into them thats why you have a charger with a circuit that can lower the amps delivered as the battery gets closer to charged, and why most battery chargers have maintenance mode and charge mode, so you can trickle charge the battery or quick charge it.

most common reason for a battery to boil is you hooked it up backwards, sounds funny but i have seen it happen a few times when people are in a rush and not being carefull.Chargers control the amps by adjusting the voltage. It's all very simple: I = V/R (I= current, V=volts, R=resistance). I had a 2A trickle charger that would boil off the water over a few months. It's good for topping off a battery but don't leave it connected.