It is handy to have a small battery charger for your automobile, especially if someone parks it in your garage for the night with a door just slightly ajar. In that case, the dome light will remain on all night and the battery will be very low in the morning.
I made this charger when I ordered some electronic parts and received a 120 to 12 volt AC transformer with center tap. Sending it back would have cost as much as the transformer. Similar transformers can be found at places like Radio Shack. The transformer puts out about 3 Amps., so it is ideal as a trickle charger. A charge will require about 12 hours. But, it has gotten me out of several jambs. Some friends have also borrowed it when their batteries were dead and it worked for them.
The center tap allowed the output to be either 6 or 12 volts. At the time I made this charger I helped to maintain an older farm tractor with a 6 volt electrical system.
Note: The output of the transformer is actually about 13.4 volts. When the voltage passes through the diodes in the rectifier it drops 0.6 volt for each of two diodes to roughly 12 volts. If you look for a 12 volt transformer you may at first be frustrated because you can find only 13.4 volt transformers.
I made this charger when I ordered some electronic parts and received a 120 to 12 volt AC transformer with center tap. Sending it back would have cost as much as the transformer. Similar transformers can be found at places like Radio Shack. The transformer puts out about 3 Amps., so it is ideal as a trickle charger. A charge will require about 12 hours. But, it has gotten me out of several jambs. Some friends have also borrowed it when their batteries were dead and it worked for them.
The center tap allowed the output to be either 6 or 12 volts. At the time I made this charger I helped to maintain an older farm tractor with a 6 volt electrical system.
Note: The output of the transformer is actually about 13.4 volts. When the voltage passes through the diodes in the rectifier it drops 0.6 volt for each of two diodes to roughly 12 volts. If you look for a 12 volt transformer you may at first be frustrated because you can find only 13.4 volt transformers.
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Signing UpStep 1: The circuit and what you need
The circuit is very simple.
I used a piece of plywood for a base. I already had a double pole toggle switch. I used a piece of scrap aluminum cabinet angle to mount the switch. Any piece of aluminum or steel could be bent to do the job. I used a 4 Amp. bridge rectifier from Radio Shack. I also got aligator clips already connected to a cord to connect to the auto battery. This was also from Radio Shack. The AC cord and plug came from a neighbor's discarded televison set that was put out on the curb on garbage day. You will need some screws, soldering iron, and a hot glue gun.
I used a piece of plywood for a base. I already had a double pole toggle switch. I used a piece of scrap aluminum cabinet angle to mount the switch. Any piece of aluminum or steel could be bent to do the job. I used a 4 Amp. bridge rectifier from Radio Shack. I also got aligator clips already connected to a cord to connect to the auto battery. This was also from Radio Shack. The AC cord and plug came from a neighbor's discarded televison set that was put out on the curb on garbage day. You will need some screws, soldering iron, and a hot glue gun.
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I have a 6/12v combo charger, meaning, I can set the charger to charge 6 volt or 12 volt lead acid batteries. I want to charge a 6 v - 4.5ah sealed lead acid battery. The chargers 6 volt setting is set for "6v-6amp" charging. Is it ok to use to charge my 6v - 4ah s.l.a. battery with this charger?
without the transformer?
i have a 12volts 3.5 amps regulated smps adapter..
can i use it to charge my motorcycle lead acid battery,,?thats 12volts2.5 AH.?
also i have confusion how much currrent will flow through the circuit..,, i know that the 3.5 amps ooutput of my adapter means that it can supply currents upto this,, but how do i controle the current..?
and at what point do i stop charging ,, i mean at what battery voltae level should i stop.,,, if my battery is unloaded..?
thanks
As regards knowing when the battery is fully charged, you could get a hygrometer made for measuring the specific gravity of the battery acid, unless the battery is sealed. Do you need the battery to be fully charged, or just charged enough to start the motorcycle? The motorcycle's own charging system should complete the charging if you go for a long ride. I would think you can know when the battery is pretty well charged by trial and error. After an attempt or two you should have a pretty good idea of how many hours are needed to charge the battery.
A fully charged 12V battery will read 12.6V with a voltmeter on open circuit with no load or charger connected to it.
Let me see if I can get a mu in my comment.
μF
BTW way Phil I never knew you were such an electronics mavin. Great job on this. I'm going to rate it high.
Your battery charger is the first stage of a lot of power supplies. I see in your comments people asking how to add the second stage, which would be a capacitor filter. After that all you need to add is some regulation and you've done it all!
I put up an article which is a bit more complicated than maybe it should be but it covers all of the bases. If you can ignore half of it then it is about as simple as it gets:
http://www.instructables.com/id/Dual-POS-NEG-Power-Supply/
You should be able to spot in the cover image some of your battery charger circuit, namely the transformer and the rectifier bridge. Then it goes to a filter stage, and finally ends up on the circuit board where there is a regulation circuit.
I have to find a picture of the first regulated power supply I made when I was 12 or so and put it here :) It is pretty ugly but we all have to start somewhere.
You're old enough to maybe know what the metal part used to be that I made the chassis out of. I had zero metalworking tools back then. I was lucky if I could drill a hole in the stuff.
I've since spent some years working on increasing my metal working abilities. Most of what I can do now is just to facilitate my electronics.
Now I'll add a bonus picture of what I am working on now. I'm getting holes pretty close to where I want them lately.
I have here a transformer from an old UPS (Belkin 550VA), I just wondering if I can use it as a battery charger, my problem is I cannot locate the PCB connected to it(to trace the flow of AC/DC). Available information of transformer I have here are in one side there are 3 wires Blue, Brown & Red on the other side Black, Red, Brown, yellow and Blue.
It has also a label on the top
080-48172-00
GP 0751
Class B Viking B-2
E210832
Please help, Thanks!
I am guessing the 120 volt primary windings are at the center of the coils next to the iron core of the transformer, and that it connects to the blue, brown, and red wires. One of those three could be a ground to the frame of the transformer. Check to see if any show a no resistance reading when the meter is connected to a wire and to the frame of the transformer. The other two would be the 120 volt AC leads. Take a resistance reading between the ends of the two remaining wires. I would expect a reading of 20 to 30 ohms, if they are the primary AC leads. Do the red, blue, and brown wires appear to go deep into the center of the coils, or do they appear to connect to the outer part of the coils (as if they connect to the secondary)?
Once you have determined which leads are the primary AC leads, connect the transformer to power and check the AC voltages between pairs of the other leads. If you wish to be extra safe, try to determine the gauge of the wire in the coil you assume is the 120 volt coil. Look on the Internet for a table that will give you the maximum safe amperage that wire can carry. Get a fuse rated at that or a little lower and put it inline with your power cord. Then if there is any danger of burning up the transformer for any reason, the fuse will blow and save the transformer.
I hope this helps.
With the auto transformer I can constantly gradually build up to full power. I also use a light bulb in line with its output as a current indicator, limiter, and ad hock fuse. If it starts glowing really brightly I know something is up. So far so good!