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Design Energy value in BQ34Z100 for 12V 60Ah battery

Ilja Lavrukov
Prodigy 160 points
Other Parts Discussed in Thread: BQ34Z100EVM

Hello !

 I am evaluating BQ34Z100EVM board with LiFeYPO4 12V 60Ah battery.
What value should I set for Design Energy after setting X10 bit to 1 and entering Design Energy Scale = 10?
The battery is LiFeYPO4 12V 60AH http://www.ev-power.eu/LiFeYPO4-batteries-12V-1-1/Lithium-Battery-12V-60Ah-WB-LP12V60AH.html?cur=1
Actualy it is 4 cell battery (3.2V each cell, Chem ID 0421) Are my calculation right?

(60000 mAh) x (3.2 V) x (4 cells) = 768000 mWh = 76800 cWh

Anyway value 76800 is out of range and couldn't be written into Design Energy data flash!

 

Thanks in advance,
Ilja

  • 0
    TI__Guru 73830 points

    The Design Energy is cell based, so you would not multiply it by 4 cells. The device will take care of that. Yes, you should enter the parameter after the appropriate X10 settings have been made.

  • 0 in reply to ThomasCosby
    Prodigy 160 points

    This way I am reading 1 cell Availible Energy in cWh, am I right? After that I can multiply it by 4  in host controller.

    Could you check if another parameters are right for LiFeYPO4 12V 60AH battery?

    Design Capacity: 6000cAh
    Design Energy: 6000cAh x 3.2V  = 19200 cWh

    Number of Cells: 1
    Pack Configuration: 09E1

    Voltage divider: 17000 (after voltage calibration: 19312) mV

    Flash Update OK Cell Volt = 2800mV * 4 * 5000 / 19312 = 2899 mV

    Load Select: 3 (I choose this because we want to use PWM load. Am I right?)
    Load Mode: 1
    Cell Terminate Volt: 2800mV
    Qmax Cell 0: 6000cAh

    ZIP-archive of gg-file is also attached.

    2013.03.21_Winston_12V_60AH.zip
  • 0 in reply to Ilja Lavrukov
    TI__Guru 73830 points

    You assumptions and calculations look correct, except for a couple of things. The voltage divider would initially be set to the maximum cell stack voltage. For LiFePO4, this would be 3.6V x 4 = 14400 mV. But, you used the voltage divider that the device calculated from calibration so you should be okay. The second item is the Load Select. We recommend using one of the average current selections for pulsed loads. I would use either 0 or 1. Otherwise, the device may measure the current during a pulse on sample and in a null region on another sample. This can cause resistance calculation issues.