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› Electronics questions: Need help with wiring and questions about setups
12-21-2003 11:08 AM  13 years agoPost 1
helicopter34

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New Jersey, exit 82

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I am designing a box (made from a tool box) to house all the things I need for charging and starting. I have a 13 power supply and a 12 volt 7aH battery in the box . I installed a computer fan to the side of the box to give some circulation. To allow me to connect various things that require a 12 volt power source, I made something so that I can just clip things on with alligator clips. I used a block of wood and screwed eye hooks into it and connected wires to the eye hooks which will connect either to the battery or the power supply. Lets call this little device my the "output block" for ease in further description. A battery charger will just be alligator clipped onto this output block. I used a switch which can be flipped to 3 different settings. Each settings has 2 seperated pairs of connections so for each flipped setting, you can short circuit two isolated circuits. This switch controls what is connected to the wires on the output block and I have it wired so (battery)-(nothing)-(power supply). I have the cooling fan connected across the 12 volt output block with a switch on it. I have a dean female plug wired across the 12 volt battery (which will be used for charging the 12 volt battery when neccassary). I posted another post regarding how I destroyed my triton on this setup (problem was in a previous design I was able to charg the 12 volt battery while it was powering the output block). My new plan is to connect one wire from the deans plug to the other seperated short circuit pair so that this dean plug will only be "connected" to my 12 volt source battery when the output to the 12 volt output block is connected to the power source and not when the battery is powering the output block. This will keep me from ever accidentally charging my 12 volt battery from itself "fire".

Well if you followed that then thank you and hopefully you can answer my questions. I am a sophmore Mech Eng and have only taken simple electrical engineering courses so far. I am pretty confident in my knowledge of basics things, but sometimes things that work in theory don't always work in practice.

I have some more plans to stuff I want to do to the box or how to rewire it for my convience.

Ok My questions
1.) If I have a battery with lets say 12 volts fully charged, if I were to connect a 12 volt source (lets say from a wall adapter) across the battery with a diode so that when the adapter is not plugged in the battery doesn't drain through the adapter, would this work in continiously charging. Would it just charge the battery whenever the battery is less than 12 volts. What are the problems with doing this besides the obvious fact that charge current is goign to be very very tiny most of the time.

2.) If what I said above would work, then would this work for my setup. Use the same setup as I described at the top, but adjust my power supply to exactly the 12 volts and connect it directly to the my output block. The exact same thing would essentailly be happening in my setup as before when the switch is connecting the power supply to the output block, but when I have it set on battery, if the power supply is plugged in, it could be slightly charging the 12 volt battery. I would probably need to put a diode so that the battery can not discharge through the power source when the power source isn't plugged in.

3.) It is hard to find diodes that can handle over 13 amps. Could I jsut wire like 5 3-amp diodes in parrallel to handle higher current. Would this work.

4.) Those solar panel chargers they sell for your car battery or for regular batteries, how do they prevent overcharge. Are they just so weak that its so unlikely they will ever actually reach full charging by themselve or something. Is there internal circuitry to prevent the car battery from discharging through the cells when they are putting out less than 12 volts.

If I think of anymore questions Ill ask later. Thanks so much for wasting your time reading all this.

Make it idiot-proof, and someone will make a better idiot

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12-21-2003 03:07 PM  13 years agoPost 2
rscamp

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Ontario, Canada

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With regard to 1), do a search and read up on the stages of charging used with lead-acid batteries.

With regard to 2), I'm too lazy to read your whole post and document your setup in a schematic.

3) should work if the diodes are well matched, but I doubt you will want to do this after reading up on 1).

For 4), I suspect they limit output voltage (CV).

Rob (Mech Eng. '81)

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12-24-2003 03:32 PM  13 years agoPost 3
BigRagu

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Utah

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Wiring Problem

Electrical Engineering Degree $68,000

Knowing how to solve you problem $Priceless!

BigRagu

Go to the local Library . . .reference engineering & science section.

BigRagu

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12-24-2003 08:48 PM  13 years agoPost 4
Marathon Man

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West Jordan, Utah

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Dario,
Comming up North the week of New Years. You going to be flying then? Got to show you my E-Raptor
Hope to see ya out there,
Kevin

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