Designing charging controller for 12V lead-acid batteries

Discussion in 'The Projects Forum' started by JanisB, Nov 2, 2014.

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  1. JanisB

    Thread Starter New Member

    Nov 2, 2014
    i have made a capacitive battery charger that works well but I need charging controller as the entity will be left unattended.

    The charger does the following things:
    It takes 230 VAC, runs it through capacitor (charging current increases as the capacity does) and then through a bridge, the bridge is connected to the battery terminals. As a result battery voltage rises slowly (the battery is being charged).

    I would like my battery charger controller to do the following things:
    1. Charge battery through a big capacitor (~8uF)
    2. When the battery charge reaches 13.8V, switch to a smaller capacitor (something that would charge with 1mA or so). There is that peculiar thing that as the charging current drops, so does the voltage hence the next step...
    3. Keep on charging and comparing the current voltage to that of a minute ago. If the voltage has dropped (the battery is discharging) switch back to the big capacitor and repeat the protocol.

    I have little knowledge about electronics. I suspect that I might need to use a comparator for the step 2 and 3 but I have no idea what kind of comparator. And I guess that a IC555 and a capacitor for charge comparing might be needed in step three but I don't know how to wire it. As well as a relay for switching between capacitors.

    As you can see, I have many needs but little means to meet them. If you could help me at any of these steps I would be grateful.
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    A non-transformer isolated off-line charger powered directly from the 240Vac line like you describe is very dangerous. The moderators will likely close this thread, but you should take this warning to heart, and build/buy a proper transformer based charger.
  3. bertus


    Apr 5, 2008

    I am closing this thread as it violates AAC policy and/or safety issues.

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