Charging systems

[dvdljns]

I built a emergancy lighting system for my house. It works good. I used a 12 volt car battery and 12 volt lights meant for droplights. What I would like to do is hook up a altanator to charge the battery. Anybody have any ideals on how to do this.

[2.2 Straight six]

why don't you just buy a car battery charger?

[GreyGoose006]

i think the idea is to run an engine and use an extra alternator to charge the battery, although i may be wrong.

without a constant charge, i dont see a normal battery lasting too long.
of course, i'd rather keep the fridge running than a few dinky lights.

[UncleBob]

simple. Get a gas engine, put a V pully on it, and hook up an alternator.

[2.2 Straight six]

he's running 12v house lights off a 12v car battery. for powercuts.

it just seems to me that a 12v charger is far easier and more practical than connecting it to an alternator.

Q: How do you charge a 12v battery?
A: with a 12v battery charger.

it's simple.

[534BC]

It may be that he wants to "re-charge" the 12 volt battery when the power is still off. Have to use the car with cables or do what UncleBob said and use a tiny gas engine. I could picture an old junk lawn mower made into a "generator" with an alternator on it.

[Steel]

Just get the RPMS right for the alternator.

[GreyGoose006]

Originally Posted by Steel

Just get the RPMS right for the alternator.

what do you mean get the RPMs right?
an alternator will make electricity at 800 rpm.
it wont be much, but it'll do.do you mean that you have to get the RPMs to match the peak power of the alternator?

if it were me, i'd use a small engine, between 3-5 hp, and run it at idle.
then use an oversized drive pully to get the needed RPM to sustain your charge.
i'd run the engine at idle or as close to it as possible to keep the gas consumption down.remember that an alternator doesnt require a lot of power to spin, and if that is all you are using the engine to do, then 1hp or so is plenty

[UncleBob]

its more of a question of amps vs hp. The more amps you want, the more HP you'll need. optimal speed can easily be adjusted by changing the pullies, but if you don't have the power, changing the pullies will just bog the motor

many small generators have a 12V circuit BTW....but I'm not sure what price range we're talking....ie how much the OP is willing/wanting to spend on this project.

[Steel]

Originally Posted by GreyGoose006

what do you mean get the RPMs right?
an alternator will make electricity at 800 rpm.
it wont be much, but it'll do.do you mean that you have to get the RPMs to match the peak power of the alternator?

if it were me, i'd use a small engine, between 3-5 hp, and run it at idle.
then use an oversized drive pully to get the needed RPM to sustain your charge.
i'd run the engine at idle or as close to it as possible to keep the gas consumption down.remember that an alternator doesnt require a lot of power to spin, and if that is all you are using the engine to do, then 1hp or so is plenty

YEs, that's what i meant. If you dont need 140A, then get a smaller alternator.

If you want to keep gas consumption down, you'd want to pick the smallest engine that would run at WOT at peak torque making enough power to turn the alternator at the required speed.

[GreyGoose006]

what i'm saying is that i find it extremely hard to believe that it will require more than 1.5 hp to make your standard alternator produce peak power.
your standard lawnmower engine makes 5 hp or so.
thats why i suggested running it at a lower rpm.
even though the engine will be more efficient at WOT, it will always use more gas. period.

its too much math for me to figure out right now, but if i were going to just wing it, i'd use an old lawnmower engine, and run it at around 1/2-1/4 throttle, and use gearing to get the alternator up to ideal rpms.

http://www.alternatorparts.com/how_m...nator_make.htm

[GreyGoose006]

http://theepicenter.com/tow082099.html

[Steel]

Originally Posted by GreyGoose006

what i'm saying is that i find it extremely hard to believe that it will require more than 1.5 hp to make your standard alternator produce peak power.
your standard lawnmower engine makes 5 hp or so.
thats why i suggested running it at a lower rpm.
even though the engine will be more efficient at WOT, it will always use more gas. period.

its too much math for me to figure out right now, but if i were going to just wing it, i'd use an old lawnmower engine, and run it at around 1/2-1/4 throttle, and use gearing to get the alternator up to ideal rpms.

http://www.alternatorparts.com/how_m...nator_make.htm

It generally wont, for a 100 Amp alternator. So... why not get a 1.5HP motor instead of wasting gas with the 5hp motor?

Actaully, the best device to use really would be a steam engine, but that's a bit out of the realm of this discussion. Perhaps another thread about teh awesomeness of steam engines.

[GreyGoose006]

the reason for using a 5 hp lawnmower engine is that it is pretty easy to find old lawnmowers laying around if you look.

i guess you could use something like a a chainsaw motor if you wanted.

a typical lawnmower revs to around 3500 rpm. half throttle would give you something like 1700 rpm, which, if you use a 4:1 pully, will be plenty of rpms for making power. standard pullys are 3:1 i think.

[Steel]

Yeah, all that would work fine. I'd think a 50cc motor would best though, puts out maybe 2.5 horsepower, then you dont need to inefficiently run it at part throttle

Im just bustin your balls goose. The ultimate set up would be a small 2 stroke diesel turning a generator, that's if you're looking for maximum electricity from minimum fuel. But anything will work as long as its spinning the alternator fast enough. Hell, you could even hook the damn thing up to a waterwheel. Or a donkey. donkeypower all the way!