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BQ27421G1A Design Voltage & Design Energy

Frank Andersen
Prodigy 50 points

Hello,

Design Voltage

In the Battery Management Studio 1.3.40, in the Data Memory tab, class configuration->Data, there is parameter named Design Voltage, which has a default value of 3600.

In the TRM this value does not exsist, it should have been in Data->Subclass ID 48.

Do I need to change this value, I would think it should have been 3700?

Design energy/ Design Capacity

The charger charges only to 4100 mV in my system, to extend the lifetime of the battery. My battery is marked 3850mAh.

Do I then set Design Capacity to 3850 * 0,9 = 3465?

And then use the 3465 in the calulation of Design Energy ( 3465 * 3,7 = 12820)?

Best regards,

Frank Andersen

  • 0
    TI__Guru* 76230 points
    Hi Frank,
    The quick start guide explains the parameters that need to be adjusted. See link below
    www.ti.com/.../sluuah7

    The four parameters that need to be changed to ensure accurate gauging are design capacity, design energy, terminate voltage and taper rate.
    Design capacity should be set to your nominal battery capacity printed on the battery label.
    Design energy should be design capacity x 3.7 or x 3.8 depending on which flavours of the bq27421 you are using. Note the different flavours corresponds to different charge termination voltages for the battery as explained in the data sheet.

    Pls it is very important to thoroughly review quick start guide i posted in the link above. It will save you a lot of future headaches.

    thanks
    Onyx