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  1. #1
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    Discharge circuit, dump circuit

    hello

    im looking for a circuit that can remove access power from a battery, but i can not find it anywhere.
    im not that competent in designing circuits so i wil try in forum.

    maybe someone have a circuit that i can use.

    i did not ask about safety, i did not ask about other ways of doing this, i only ask for circuit and discussing about discharge circuit please respect that.


    ok i have a few "requirements" for way of function
    no programming
    pwm based discharge
    pwm 0-100% (not critical can be for example 10 - 90%)
    pwm start voltage adjustable if batteryvoltage 5v over start voltage =100% pwm
    pwm start voltage adjustable dc240v - dc265v (example start 265,05=1%pwm 270=100%pwm
    pwm ramp up and down slowly
    pwm is limited by a current shunt adjustable from 1A to 100A
    pwm frequency not critical about 3khz


    explaining of circuit work:
    start voltage adjusted to 240vdc
    current limit set to 10A

    voltage increase to 240,1vdc
    pwm start 2%

    voltage increase to 241vdc
    pwm adjust slowly to 20%

    voltage increase to 242vdc
    pwm try to adjust slowly to 40% but the current limit stop and hold the pwm at 30%

    voltage increase to 243vdc
    current limit still hold the pwm at 30%

    voltage decrease to 240,5
    pwm adjust slowly to 10%

    voltage decrease to 240
    pwm stop

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  2. #2
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    Re: Discharge circuit, dump circuit

    Hi,

    A forum is not meant to do others jobs. It is meant to help to rectify mistakes.
    If you want others do your job you should post in the "jobs section" and consider to pay for the job.

    Klaus
    Please donīt contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



  3. #3
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    Re: Discharge circuit, dump circuit

    you might want to start with something like this electronic load 3kW +

    http://www.pwrtrnx.com/index.cfm/4,457,html



  4. #4
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    Re: Discharge circuit, dump circuit

    Quote Originally Posted by Easy peasy View Post
    you might want to start with something like this electronic load 3kW +

    http://www.pwrtrnx.com/index.cfm/4,457,html
    there you have it, what i want is basiccally a dc load but need to be controlled by the input voltage



  5. #5
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    Re: Discharge circuit, dump circuit

    we purchased several for Li-ion testing, and they modified one for us, so we could input 0-10V for 0 - 100A

    apparently they can do constant R too, one of ours is 450V rated for PFC testing ....



  6. #6
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    Re: Discharge circuit, dump circuit

    Quote Originally Posted by Easy peasy View Post
    we purchased several for Li-ion testing, and they modified one for us, so we could input 0-10V for 0 - 100A

    apparently they can do constant R too, one of ours is 450V rated for PFC testing ....
    it should be a simple driver circuit for that device, do you have the circuit diagram avalible?



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  7. #7
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    Re: Discharge circuit, dump circuit

    Um, no we don't - we looked inside, 64 mosfets, with drivers, control card, fan drive ( varies with power/temp ), over temp protection, reverse input protection, etc ...

    they made a mod on their board to accept 0-10VDc for 0 - 100A, via BNC connector on back, metal case is fully isolated from inputs ( to 500V )



  8. #8
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    Re: Discharge circuit, dump circuit

    Quote Originally Posted by Easy peasy View Post
    Um, no we don't - we looked inside, 64 mosfets, with drivers, control card, fan drive ( varies with power/temp ), over temp protection, reverse input protection, etc ...

    they made a mod on their board to accept 0-10VDc for 0 - 100A, via BNC connector on back, metal case is fully isolated from inputs ( to 500V )
    thats more than what i was thinking.

    here is a drawing to show what i was thinking,
    offcorse it do not work bechause i do not have the knowlege to make it correct but the design or how to do should be possible this way.
    240v is stepped down to 0v and 245v wil then be 5v, potentiometer is there to adjust the 0v from 240 to 265v and the 5v wil be 5v higher as in the first example.

    0-5v is amplified by opamp, zener is there to pull down the voltage if the 0-5v should be higher than 5v.
    0-5v pwm circuit 0v=0%duty 5v=100%duty.
    pwm output have a pull down resistor to shut the SCR off when pulse is low.

    shunt feedback the current via transistor and pull down the 0-5v if current is over setpoint by the potentiometer close to the shunt

    then finally the battery and load is connected to the SCR input and output.

    SCR is a NKT110-16A

    Click image for larger version. 

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  9. #9
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    Re: Discharge circuit, dump circuit

    Hi,

    an SCR is made for AC operation (at least the current needs to go down to zero periodically), it canīt be used for DC this way.
    And an SCR canīt be (usefully) controlled by a PWM signal.

    Klaus
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  10. #10
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    Re: Discharge circuit, dump circuit

    Quote Originally Posted by KlausST View Post
    Hi,

    an SCR is made for AC operation (at least the current needs to go down to zero periodically), it canīt be used for DC this way.
    And an SCR canīt be (usefully) controlled by a PWM signal.

    Klaus
    thnks, i have a large igbt in storage somewhere witch i can use as well



  11. #11
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    Re: Discharge circuit, dump circuit

    what is your load exactly? as above if SCR gated on it will stay on until current falls to essentially zero, i.e. you cannot turn an SCR off once gated on ...



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  12. #12
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    Re: Discharge circuit, dump circuit

    Quote Originally Posted by Easy peasy View Post
    what is your load exactly? as above if SCR gated on it will stay on until current falls to essentially zero, i.e. you cannot turn an SCR off once gated on ...
    yes i got several tips that scr wil not work.
    so i wil replace that bit with igbt



  13. #13
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    Re: Discharge circuit, dump circuit

    Just be careful if you are turning off current quickly with the IGBT and the load has large loop area, you will get over-volt spikes on your IGBT ...



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