Solar Charge Controller

Discussion in 'General Electronics Chat' started by Shapath, Jul 18, 2010.

  1. Shapath

    Shapath Thread Starter New Member

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    Hi all,
    I am trying to design a simple charge controller for my solar panel of 5Watt. The battery is 12V4Ah sealed lead acid battery.
    I will be really helpful if any1 provides me with the schematic of a charge controller and/or explains me its operation.
    Thank you
    ψ:)
  2. timrobbins

    timrobbins Active Member

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    How simple do you want to go, and what have you found out so far?

    You will also need to indicate the PV panel specs (eg. Isc, Vpp, Voc at least), and the battery manufacturers recommended charging voltages and max charging current, and the load profile.

    The simplest controller is yourself and a switch (and preferably a voltmeter). Anything more requires you to understand why you would choose a particular charging solution.

    Ciao, Tim
  3. sage.radachowsky

    sage.radachowsky Member

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    Like Tim said, the simplest is if you sit there and connect the wire when the voltage is higher than the battery.

    But let's get more info. What is the nominal voltage of your panel? I assume it's > 12V. If it's lower then you need a boost converter.

    If the panel voltage > battery voltage, then the simplest thing you can do it use a diode, to allow current into the battery but not to backflow when there is no power coming from the panel.

    Your panel is only 5W so that may be enough. You may not need to worry about overcharging, which can damage the battery. Lead acid can handle a small current as a trickle charge, without damage. Too much will cause damage. So the next level of charge controller has overvoltage protection. This will disconnect the panel when the battery is full.

    Another useful part is really a "load controller" -- that will disconnect the load when the battery is drained too far. This will also protect the battery from damage from going too low.

    Then, there is another level of complexity, if you really care about efficiency. There is "maximum power point tracking" (MPPT). This will use a buck or boost converter to match the input voltage to the best point to extract the most power from the panel, and convert it to the voltage that will best charge the battery. It can sometimes give you more than 30% more power from a panel, and helps to adapt to changing light and temperature conditions, and battery levels. But it is more complicated. Usually it uses a microcontroller.
    Shapath likes this.
  4. BMorse

    BMorse Senior Member

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    Dual opamp circuit would be sufficient as a Charge/Dump controller for this small panel and battery system...

    Check out my charge controller here >> http://www.morse-code.com/id184.htm

    B.Morse
  5. Bernard

    Bernard Senior Member

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    Last edited: Jul 19, 2010
  6. timrobbins

    timrobbins Active Member

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    BMorse - you don't explain on your webpage what you do with the relay wrt the panel and the load (in line with the earlier introduction). You also don't mention the other main types of PV controllers - mppt and open-circuit pwm type. You don't mention the influence of load on the voltage set points, or why you chose those voltage set points.

    Ciao, Tim
  7. sage.radachowsky

    sage.radachowsky Member

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    Shapath likes this.
  8. BMorse

    BMorse Senior Member

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    Well it was not meant to be a complete tutorial or even any kind of tutorial strictly for SOLAR power, if you would have noticed, I am using it on a Permanent magnet DC motor generator set up as a windmill, so PV and MPPT do not apply with my project (It could, but not necessary).... but the charge controller could be used with a solar panel....


    As for the relay, I am just diverting the power coming from the generator with it, between a battery bank used to power garden lights and a low voltage water heater...


    I chose those set points for charging and discharging because that is what was specified for the type of batteries I used according to manufacturer specs...
    B. Morse
  9. Shapath

    Shapath Thread Starter New Member

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    Thanks Tim, Sage, Morse and Bernard!!!!
    thank you guys a lot....:D!!!
    I was very busy for the last few days so cant check here and respond to you guys and I am sorry for that.
    I guess I will try Sage circuit and will see the output. The things that you have mentioned in your 1st post is true and expect the tracking part i m trying to design the circuit.
    n B.Morse thanks to you also for your circuit also...I will also try your one and will let you know the results.
    Bernard I will check the link and will let you know.

    And one more thing....can any1 here plz tell me whether these is any way i can get these post reply in ma mail box?den i can easily check the replies everyday...:D!!

    n thanks again
  10. BMorse

    BMorse Senior Member

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    Shapath: Click on the link at the top of the first post where it says "Thread Tools", click that, then click "subscribe to this thread", when a new window opens up, select "Instant notification by email", then click "Add Subscription"....

    B. Morse
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