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Ghettofabulous battery charger? Can I do it?

635 Views 19 Replies 14 Participants Last post by  JNXtheband
Get this idea of mine:
I get pride from building things that work even if they are eccentric, and if they save me money, even better..
I propose a battery charger made from a VW A2 type alternator and regulator, a belt, a motor pulley, and an AC motor. The thing would be mounted on a wood or metal platform with some provisions for vibration dampening, but basically it would be configured using the motor's output and the pulley ratios to get the alternator turning around 3k RPM's, which should be satisfactory, no? And then I'd run a ground off the alternator case and a positive off the post with heavy gauge wire to two copper posts mounted to the base (insulated if it's metal). To connect the charger I'd simply disconnect the battery cables from the car, and attach it to my charger via jumper cables.
Far fetched, or will it work?
I don't care how noisy the thing is..
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Re: Ghettofabulous battery charger? Can I do it? (wyldejackyl)

well, it could work. Remember that A2 alternators actually route wiring through the cockpit instrumentation and require that to be present for alternator operation (you could bypass that of course, no reason to rig up a dashboard).
Other than that, yes, it's technically possible. Energy efficient, practical, reliable, economical, wise, et al, probably not, but that wouldn't be the point, as you say.
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Re: Ghettofabulous battery charger? Can I do it? (wyldejackyl)

just run ur schematic by macgyver first
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Re: Ghettofabulous battery charger? Can I do it? (canadian_dubber)

The only problem is the initial exciter circuit. Basically to get a basic bosch alternator working you need 12v + running through a light bulb (like the alternator light but any 12v light bulb will work), grounded through the connection for the blue wire. 12v+ goes in, excites the alternator, and alternator starts making power, pushes 12v+ back through light bulb circuit, turning light out.
Once you figure out the 12v+ for the exciter circuit, you're all set.
Re: Ghettofabulous battery charger? Can I do it? (Nason)

So it's that damn light blue wire that goes to the small post that's going to ream me, eh? I suppose I could use some power from the dead battery for that light bulb, but if the battery is really THAT dead, which is probably will be...that's a no-go.
How about this:
All alternators are basically the same output, right? About 14v with so many amps. If I found a GM type or other cheap, domestically available unit (with the same approximate output amperage), would that work? Also, how about a generator? It is my understanding that the only difference between the alt and gen is that the latter puts out DC straight, while the former puts out AC that must be rectified. If there's more to it than that, lemme know - I think I fell asleep in that section in physics, since I have no recollection of it whatsoever.
But could I use an old generator, say from a Type 1 even? Not a ton of output, but all we're doing here is charging a battery.
If I wanted to build my own solid-state one, I'd need either a big transformer or a couple of smaller ones, 7812 voltage regulators with TO-3 cases and a huge heat sink..and some filtering capacitors..and even then, wouldn't my output be limited to only a few amps? That's why I was considering the ghetto version. I suppose I could just BUY a battery charger..but then again, you can just BUY a fast car too - no fun. The fun is in construction.
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Re: Ghettofabulous battery charger? Can I do it? (wyldejackyl)

Wouldn't it be easier and less time consuming just to shell out 30-40$ for a cheap battery charger at wal mart or something? Just my $.02
Re: Ghettofabulous battery charger? Can I do it? (brandon002)

Because I have parts laying around and time to create something unique - another thing to build to say "I did it the unconventional way" and it works just fine (albeit a bit noisy). I hate being a slave to what other people design, that's why I'm a designer. So I figure, what the hell..let's build a battery charger!
I'd rather build my own power supplies/crossovers/whatevers than buy them, and I can be assured of the quality because I'm the one that made the damn things, not someone paid a nickel a week in China to make them in a factory who doesn't care too much about quality as much as cost.
And wouldn't you want a nice noisy battery charger in your garage? Your friends ask you if it's some kind of compressor..nope, it's just chargin' batteries.
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Re: Ghettofabulous battery charger? Can I do it? (wyldejackyl)

It swill work,
At the shop I used to work at we had a hand truck with a 2HP gas engine turning a diesel truck alternator. We could easily move it anywhere in the yard and charge batteries. The other guys would take it to the track with them incase the cars batteries died befor a race, saved their butts more than once.

[Modified by kevwithoutacorrado, 11:08 AM 6-11-2002]
Re: Ghettofabulous battery charger? Can I do it? (kevwithoutacorrado)


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Re: Ghettofabulous battery charger? Can I do it? (lyledriver)

When I was like in 5th grade, I came up with that thing too! I figured, if you could plug a car in and start it using external power..that it should be able to run off it's own electricity indefinitely, without a battery. However, I vaguely remember having a new ass hole reamed for me by my high school professor when I proposed such a thing..
He said that no matter how insignificant the friction in bearings, loss of energy due to heat in the wires, etc..eventually, EVENTUALLY..the damn thing would stop working. I never tried it on my own..but then again..maybe I should make this charger for the sake of revolutionizing the auto industry!
Propetual motion cars!
So the alternator thing will work, eh? Could I use any alternator that is putting out 13-14v then? What speed should the shaft turn at (alternator shaft that is) to put out the most power?
Re: Ghettofabulous battery charger? Can I do it? (wyldejackyl)

Errr......it is not perpetual motion 'cause when you burn the gas you get power. most gas cars are like 20%-25% efficient. A gallon of gas has ENORMOUS stored energy in it and we waste most of theat energy in a car engine. Good thing Gas is cheap.
Yes you could start a car on outside power and run it off of the Alt.
You should have smacked that teacher.
But the Batt acts as a resevoir/buffer for other electics to run from.
Re: Ghettofabulous battery charger? Can I do it? (fiorya)

Okay, so I'm the idiot for not explaining this time..
I meant..
have an ELECTRIC car running on a motor and an alternator. Alternator provides some parasitic drag but can power the motor, and it's started externally. I neglected to take into consideration the alt would have to be about as large as the motor in order to run it anyway..thus, parasitic would start meaning the main load.
But you're all saying this alternator thing will work?
Re: Ghettofabulous battery charger? Can I do it? (wyldejackyl)

yeah...that too.
BTW all of the new hybrids extract electricity from the braking mechanisms to extend battery life
Re: Ghettofabulous battery charger? Can I do it? (fiorya)

Your thing will be so inefficient that you'll spend more money on the electrical bill than you'll save by not buying the wallmart charger.
If you really want to build something useful, why not get an EE book and build yourlef a charger the way it's supposed to be built -- transformer plus regulator.
Re: Ghettofabulous battery charger? Can I do it? (nicuss)

Yeah, you'll be wasting a whole bunch of energey converting the electricity into mechanical motion and then back into electricity..
But if you really really want to do it, I'd suggest using a magneto instead of an alternator. The magneto has a permanent magnet in the armature rather than an electromagnet eliminating the need for an initial field current power source or exciter.
Re: Ghettofabulous battery charger? Can I do it? (Spinne16v)

Yes, It will work, A small gasoline engine turning the alternator will output electricity. I used to drag on around a truck shop and start diesel trucks with one. It was home made on a small hand truck. It was noisy and shook alot, because we made it in the shop on afternoon for fun (and usefullness.)
Re: Ghettofabulous battery charger? Can I do it? (kevwithoutacorrado)

wow that is one amazing picture!!
Re: Ghettofabulous battery charger? Can I do it? (lyledriver)

hmmm my version is cheaper...

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Re: Ghettofabulous battery charger? Can I do it? (wyldejackyl)

Hi all,
If you want to build a heath robinson DIY battery charger for fun, then by all means go ahead. However, commercial battery chargers have cool features like short circuit protection, over-charge protection etc.
Just don't complain when you short circuit the output by mistake and end up doing some impromptu arc-welding !!!!
Re: Ghettofabulous battery charger? Can I do it? (RCMits)

quote:[HR][/HR]hmmm my version is cheaper...

LOL i woke up my neighbors laughing about that one
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