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Automatic battery charger

Discussion in 'Power Electronics' started by Michael Blackburn, Feb 2, 2016.

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  1. Michael Blackburn

    Michael Blackburn

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    0
    Feb 2, 2016
    Hey everyone. I was just wondering if anyone knows a way to trick an automatic 12v car battery charger into being a manual? I want to use one as a power source for electrolysis, but I don't want to deal with passing it through a battery. Any help would be greatly appreciated!
     
  2. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    I would suggest using an old PC power supply instead... It will have an upper current limit and fault protection.
    A battery charger is not a 'power supply' and will vary it's output considerably depending on what it senses on it's output... They are not dumb chargers, if they 'think' there is a battery they will charge it, and if the battery is full they will turn down considerably and trickle charge.

    If you are really set on using this device, we would need a circuit diagram to even be sure this can be done...

    Ideally, if you will be playing with conductive liquids and any device that plugs in the wall, you should do so with an isolation transformer, or at least a GFCI outlet. Supervision never hurts to have either.
    If you want to use a car battery, or combo battery/charger use a fast acting fuse, or a device that has fault protection.
     
  3. Michael Blackburn

    Michael Blackburn

    2
    0
    Feb 2, 2016
    Thanks for the reply! I've been tossing around the idea of using a pc power supply. The battery charger I have has a 2,10, and 50 amp setting. I've been using the 10 amp setting and passing it through a car battery so far, but I'm afraid of it overheating in the warmer months. Its a harbor freight charger so I doubt any sort of schematic can be obtained for it. From my understanding, the auto shutoff occurs when the current from the battery reaches a target voltage. If I ended up trying to continue to make this work, would a resistor placed in line to the battery work or do you think that's a bad idea? I know a lot of people who use electrolysis but it gets harder for them to get a manual one. I'm trying to come up with a solution that uses an auto charger but removes the battery from the picture. I'm sure a lot of people wouldn't want to mess with trying to combine all the wires of a pc power supply together then run heavy gauge wire off them to the tank lol. I know a "little" about electrical stuff but I'm no expert. Ideally I'd like to be able to run 30-40 amps to the tank, because the 10 amps I'm running now is taking forever for the cleaning process. The 50 amp setting on my charger is intended for jumping a dead vehicle and it shuts down after a few seconds.
     
  4. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Personal preference. I'm certain you are using the battery in 'parallel' with the tank in order to get the charger to turn on. Or did you connect everything in series?

    In a parallel situation, where the charger positive, is connected to the battery positive which is also connected to your electrolysis device... this type of setup will split the current from the auto-charger... some will go through the battery and some will go through your tank. This all depends on the current level of the battery and the resistance of the electrolysis. You also run the risk of having the battery dump many more amps into the tank if the resistance is too low... This would result in quickly killing the battery, then having the auto-charger attempt to keep it alive with the 10A setting you are using.

    I'm sorry I don't know the charger you are using too well, it could very well have a voltage sense on it, or it could simply be monitoring it's own voltage output as it pumps out 10A ... you may be able to mimic a 'battery' by using a solution that offers higher resistance, or by using a high power resistor in-line with one of the leads to the tank. This would only work if the charger monitors it's own output instead of attempting to read the 'battery'.

    You can find more information on this by looking up charge characteristics of Lead-Acid batteries. Please note though, that any resistors you use will get VERY hot and will most likely need to be very large. However, the benefit here is the current limiting of the charger which could be very helpful.

    Then there is the PC power supply... Most cheap supplies can easily put out 10A, and this would be direct without the need for a battery. You could cram 10A down a 20Guage wire if you wanted too. Many other power supplies can put out close to 20A on the 12V rail only... If you are curious, just look at the sticker on the side. It will tell you the capability of each voltage. The tricky part here is the need to cut and tie together a few strands of same color wire, which really isn't so bad.

    I've got a couple questions for you though... how do you know how much current is going through the tank if you have the battery connected as well?
    Can you adjust your mixture to change resistance? I should mention that according to ohm's law, if you want more current through the solution, you will need to increase the voltage, or decrease the resistance.
     
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