Constant Current Lead Acid Battery Discharger

Discussion in 'General Electronics Chat' started by sa87, Jun 1, 2012.

  1. sa87

    Thread Starter New Member

    Jun 1, 2012
    2
    0
    I need to design a constant current Lead acid battery dis charger.
    Specifications of the 12V Lead Acid Battery discharger
    discharge current rating 0-8A
    We need to get the constant current from the battery through out the discharge period.
    I want to know about a suitable circuit diagram and parts for this design.
    Can anybody help me.....
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    Will be pretty large and take some power transistors. You will be dissipating about 100W in the transistors during battery discharge so you will need a big heatsink and a fan.

    I would use N channel mosfets as a current sink in the negative return lead from the battery. You can parallel FETs to spread the power out.
     
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  3. Smoke_Maker

    Active Member

    Sep 24, 2007
    126
    15
    Have you got any schematic of where you are starting from?? I have seen several of them, the most successful used a PIC. The basic set up is to measure the current with the PIC and PWM a output to control your load current.
     
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  4. #12

    Expert

    Nov 30, 2010
    16,284
    6,797
    Here's a fancy one. If you like it, fine. If not, start removing options.
     
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  5. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I agree with all that except for putting the transistors in the negative lead.
    The current sink has to be in parallel with the battery.
     
    Last edited: Jun 1, 2012
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  6. Externet

    AAC Fanatic!

    Nov 29, 2005
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  7. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
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    Yes, shouldn't post at 1AM. It has to be connected across the battery terminals.

    The one shown in the circuit in the previous post above by #12 has the right idea.
     
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  8. sa87

    Thread Starter New Member

    Jun 1, 2012
    2
    0
    I need to design a battery test bench to perform capacity test for starting type lead acid batteries.
    Full charged lead acid battery 12.6V and do the constant current discharge until 10.5±0.05v
    According to the battery capacity discharging constant current should be able to change and these data should be able to take to computer. Timer should be included and also the voltage cutoff to stop the discharge at 10.5±0.05V. This should be automated one.
    I was thinking about to do this using a switching dc load which keep the constant current through out the test when the battery voltage change. If somebody can give me a suitable switching load design to perform this it may be very helpful. Thanx
    Adding something more about the project have to be done. The discharging constant current may vary from 1A to 8A. So this design must be suitable to discharge any constant current ranges from 1A to 8A.Can any body help me with this ............
     
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