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A final look at the protection PCB for the 630F and 700F 2.5V Nippon Chemi-Con supercapacitors. In the previous video, I missed a tiny track between the TL431 ref pin and Vcc (or CAP +). So this time I take a look at the internals of the TL431 and add a red indicator LED to the circuit.

By Julian

Youtuber, shed dweller, solar charge controller aficionado

11 thoughts on “700f super capacitor protection pcb – reverse engineer update”
  1. Avataaar/Circle Created with python_avatars New Micro Electronics says:

    Very good explanation, I am from sri lanka,❤😂

  2. Avataaar/Circle Created with python_avatars S R says:

    I'm offgrid on solar. If you crack the supercapacitor pack that'll make my day … To run my washing machine

  3. Avataaar/Circle Created with python_avatars Robert ALLAIRE says:

    Hello Julian, can you explain me how this circuit can regulate the voltage of the capacitors for an perfect balancing. Indeed it seems to miss the 2 resistors of 180k and 12k that are R4 and R5 and that should join the "leg" reference so that the transistor driven by the TL431 can prevent any voltage to rise above 2.7v on the super capacitor. They would be unfinished circuits.
    I resume, the "reference" leg of TL431 is apparently not connected.
    Conclusion: your TL431 can not regulate the voltage!

  4. Avataaar/Circle Created with python_avatars PicoNano says:

    This is not a protection circuit. It's a balancer.

  5. Avataaar/Circle Created with python_avatars hee joong kim says:

    셀 밸런싱에 대한 영상과 자세한 회로 해석 설명(못 알아듯지만) 잘 보았습니다.
    I watched the video about cell balancing and the detailed circuit analysis explanation (though I don't know).

  6. Avataaar/Circle Created with python_avatars Deepa V says:

    Sir,

    Its a nice video. I brought the balancing board. I tried testing the balancing board for verifying its regulation by connecting the supercapacitor and a variable power supply to the same slot and used a multimeter to measure the voltage of the supercapacitor. Not sure if the method is right because the multimeter would not be able to show the actual voltage of super cap as the source is also connected to same point. By this method, I find the voltage rising above 2.8V. Didnt check after that. Is there any way to ascertain that regulation is happening? What is the max applicable voltage to the board for the regulation to happen?

  7. Avataaar/Circle Created with python_avatars Stray Dog says:

    protection voltage has to be Vref+Vbe=2.5V+0.7V=3.3V. It is higher than 2.7V which is cap max charge voltage. The design is not suitable for 2.7v cap.

  8. Avataaar/Circle Created with python_avatars Ryder FGz says:

    what is type of PNP 8550 and NPN D882 is? I gonna make DIY protection board by myself can y'all tell me?

  9. Avataaar/Circle Created with python_avatars Ekiskalibur Nirvana says:

    That circuit is especially for series connected caps. when one capacitor charges before others, it gives a path for the current to flow to other caps.

  10. Avataaar/Circle Created with python_avatars tucan man says:

    close the blinds we cant tell with the sun

  11. Avataaar/Circle Created with python_avatars Blacklab412294 says:

    I am thinking You need to treat that RED LED and the 8550 and the D882 like they are all in series == VoltLED + Vdrop 8550 + Vdrop across the gate of D882 >>> to get a R { in series with the LED} = (Vs – VLedTotal ) / I . I know R is going to be really small, but it might be important to prevent your magic smoke from escaping from the LED.

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