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Not rechargeable battery, calculating the remaining capacity

dave813
Prodigy 40 points
Other Parts Discussed in Thread: BQ26220

Hello,

I have a not rechargeable battery (LSH20) with capacity of 13 Ah and a BQ26220evm-001 (evaluation kit of battery monitor).

I'd like to calculate the remaining capacity and read the power consumption.

what is the correct way to set the BQ26220, in this case ?

thanks 

  • 0
    Prodigy 40 points

    Hello,

    I wonder how do you set the DTC and DCR registers of BQ26220?

    these are the register  that deal with the discharge phase of the battery, but I don't know how to calculate

    the capacity  [A h] and the time [h] of discharge.

    thanks

  • 0 in reply to dave813
    Prodigy 20 points
    Hello,

    To calculate the capacity of your battery you need to take the velue in the DCR register and the value in the DTC register.
    In the datasheet of the BQ26220 you can see that the DCR counts at a rate equivalent to one count per 3.05μVH. And in the DTC register 4096 is one hour.
    You also need the value of the shunt resistor.

    So for example (you can find this example in the datasheet of the BQ26220 page 8) :

    - 8000 in DCR register
    - 4096 in DTC so 1 hour
    - Shunt resistor = 20 mΩ

    8000 * 3.05*10^-6 = 0.0244 V or 24.4 mV
    With the Ohm's law you have : I = 0.0244 / 0.0020 = 1.22 A
    Q = I*t = 1.22 A * 1 H = 1.22 AH
    Remaining capacity of the battery = 15 AH - 1.22 AH = 13.78 AH

    I hope that it's help you.

    Best regards.