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Home made battery charger

5K views 6 replies 3 participants last post by  lanierledford 
#1 ·
I once had a friend build a battery charger. He used and electrical plug, some electrical wire, two light bulbs, and a diode two alligator clips. when he hooked it up, the lights burned dim at first as they charged up ( the batterys), the lights got brighter. He said the diode stopped the current from alternating, changed it from ac to DC. It didn't over charge because the bulbs were using the current when the batteries charged up. My question? what size diode or number, and what goes where in the circuits
 
#4 ·
battery charging

Thanks 4jaw chuck and jmhollis, its strange how when its me, I'm cheap, when its you, you're thrifty. I have a 400 amp charger and jump starting battery charger, but you know, that doesn't help me show my grandson how elector is changed from ac by going through a diode and changes dc. And by the way, the light bulbs are the fire extinguisher, and the safety devise . His may surpriser you, but most cars now have an alternater, which makes ac current, which is converted to dc current for the electical of cars. If its not the way it works, could someone inlighten me please. Thank you in advance.
 
#5 · (Edited)
The diode is a solid state semiconductor. When you apply voltage in excess of its threshold in the forward direction, it allows current to flow. When the polarity is reversed it will not allow current to flow. Using a single diode in an alternating current circuit creates a half wave dc output at the diode's anode. Using 4 diodes in a bridge configuration would give you a full wave output which would require less filtering to be useful (in this case, the battery is the filter). Radio Shack sells both diodes and bridges. If you really want to try this, get a 1n4001 diode or equivalent. It will give you about 1 amp half wave dc throughput. If the light bulbs are in series by themselves, each represents 50% of the voltage drop across the circuit. If we start at 110v, this gives a 55v drop across each bulb. If the total circuit uses 110 watts of power this would represent 1 amp at 110v (an example of ohm's law: i=p/e). Depending on the internal resistance of the battery under charge and the loss through the diode, putting everything in series (and restricting current flow to half wave with the diode) might allow some kind of charge to take place. I have not really thought through the circuit but I still think it is unsafe. If a light bulb breaks in the presence of hydrogen gas (formed when your battery charges), guess what happens?

If you want a great example of how a diode works, wire one into a flashlight and demonstrate that in one direction it allows the dc from the batteries to flow and in the other the bulb won't light. For an ac example, find an old power cube (cell phone charger, calculator power cube, etc) with ac output. Then wire a diode between it and a small dc motor. Show that reversing the diode reverses the motor. Use a voltmeter to measure the dc voltage resulting from the diode being placed in the circuit. Use a bridge and you will be able to draw higher dc current (with a little more wiring work). Edmund Scientific and Radio Shack both sell great beginner kits to show your grandson how all this works.

And I really do know about auto alternators, with an understanding that they include a little more than thin glass, incandescent filaments, and a diode to do their job...
:>
 
#6 · (Edited)
#7 ·
Charging the battery

Many thanks jm hollis and 4 Jaw Chuck, Jason read your replies and said he understood it, although he had to read it 2 times. I think that has to do getting your mind on what's goin on. He said he'd still like to see it work, so we're off th radio shack I'm a guessing. thanks again . gramps
 
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