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Universal Vehicle Battery Fuel Gauge

Harrie Noorlander
Prodigy 10 points
Other Parts Discussed in Thread: BQ34Z100-G1

Hello, 

I'm searching for a solution to measure the remaining capacity for batteries is personal vehicles (12V) as well as in trucks (24V).
Here, Texas Instruments provides a range of different Battery Fuel Gauges, including the bq34z100-G1, to do the job.

However, according to the technical documentation of the bq34z100-G1, it only supports a battery capacity up to 29 Ahr.
Unfortunately, batteries which are used in the automotive industry, generally exceed the supported capacity of the bq34z100-G1.

What would happen if a bq34z100-G1 is connected to a battery with more than 29 Ahr?
Will it provide an indication that at least 29 Ahr (when more is available) or will it provide a false reading.

I hope my question is clear, many thanks in advance and I'm looking forward to your recommendations.

Kind regards,

Harrie Noorlander

  • 0
    TI__Guru 73830 points
    The bq34z100-G1 can support 29Ahr capacity and 32A charge or discharge current directly. You will need to use current scaling, if your application exceeds either one of these values. If you have a 100Ah application, then the scaling factor will need to be 100 / 29 = 3.45 or more. You can use 4 or maybe even 5 to allow margin. You will scale all current and capacity parameters in the data flash by dividing them by this value. You will then scale the current when you calibrate the pack. If you use a 5x scale factor and a 10A current to calibrate, then you would enter -2000mA in the Actual Current field in the calibration screen. All reported current and capacity values will be reported scaled and will have to be multiplied by the scale factor to get the true value.
  • 0 in reply to ThomasCosby
    Prodigy 60 points
    Sir,
    For above example 100Ah is battery capacity. Suppose the capacity scaling factor is 4x. Then what is my Design capacity value.
    Design capacity : 100/29 = 3.45(4) or 100/4 = 25000mAh.
    And what about the Design Energy.....?

    Thanks in Advance......
  • 0 in reply to amar nadavaluri
    Expert 2475 points
    This e2e posting helps with the Design Energy.

    e2e.ti.com/.../2281095