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Thread: voltage and current monitering

  1. #1
    Junior Member
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    voltage and current monitering

    hi all i was wondering what the best way to maniter the voltage and current (bidirectional) of a 72v lipo pack with upto 350a current draw
    now yes i know there are other pre made ways to do this but i am wanting to intergrate it in to a system i am doing if you have any questions just ask
    i am useing the teensy 4.0 if you need to know that but am willing to change if needed

  2. #2
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    An INA230 could be used to measure current with a low side shunt. Maybe it could handle measuring 72V if you added a voltage divider.

  3. #3
    Senior Member
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    You can use the main high current wiring as a shunt, basically tapping into it at two points for a Kelvin connection. This isn't
    ideal as the tempco. of copper is quite high compared to most resistors, and high current wiring will run quite warm at times,
    and it needs calibration for the particular stretch of wire used, but is simple and robust. Make sure the two points are on the
    same stretch of wire (no connectors in the middle).

    Twenty voltage dividers is an option, but they need to be high precision (0.1% or better) to get sensible accuracy for individual
    cells - precision resistor arrays may be useful here.

    And for low current drain and to avoid unbalancing the cells they should be fairly high impedance (they will be draining power
    constantly). route them to a set of analog multiplexors to the ADC input, which needs to be able to work with high impedance
    source. Note a fairly high resolution ADC is needed if you want to detect say 0.05V resolution at 72V - 12bit seems appropriate.

    There are also chipsets for BMS functionality that are worth checking out.

  4. #4
    I have used current sensors like this for 20 amp applications.

    https://www.tamuracorp.com/electroni.../L08PD15_e.pdf

    I use voltage dividers to measure 24 volts.

    Hope this helps.

  5. #5
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    If you want individual cell (vs pack) monitoring, then the diyBMSv4 approach is worth looking at.

  6. #6
    Junior Member
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    Sep 2021
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    hi there i was just thinking could i use a teensy 3.2 to moniter indervidual cell voltage (one cell per anoglog input) then sum them togeather for pack voltage

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