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BQ34Z110 and BQ34Z100-G1 data reset when battery is replaced.

Eldes
Prodigy 130 points
Other Parts Discussed in Thread: BQ34Z100-G1, BQ34Z110

Greetings.

We are using two kind of fuel gauges (BQ34Z110 and BQ34Z100-G1) to monitor the state of lead-acid battery. In our application the battery is detachable, and fuel gauge stays in our device rather than attached to the battery package.

I have a problem with the actualization of data of fuel gauge when battery is replaced. The main problem is that some Full Charge Capacity value which gauge remembers from previous battery (say, current FCC = 1500 mA*h, and design FCC = 7200 mA*h) may stay the same after battery is replaced, which makes the following State of Charge (SoC) readout act wrong. When new battery will be in use, the gauge will count SoC down from 100% to, say, 40% and then suddenly drop SoC readout to zero. We could not allow this in our application. Additionally, I'm not sure if gauge will raise its FCC value at all.

I've experimented with the RESET command, and sometimes when I connect new battery and make RESET, the gauge sets its FCC at approximately design capacity 7200 mA*h, which is what I need. Sometimes it doesn't happen.

Please suggest how to make the gauge use the new value of FCC when new battery is connected.

  • 0
    TI__Guru 73830 points
    The gauge can "learn" a new battery through normal operation, but it was not designed to update parameters for a new battery that is a different basic configuration than the previous one. e.g. Changing the capacity from 7200mAh to 1500mAh. That is a large change for the gauge to update. It was designed to be able to replace an old battery with a new one from the same type. It can learn the new one in a couple of charge ad discharge cycles. You will need to run an optimization cycle to learn a different type of battery. i.e. A device initialized back to the original srec and Update Status = 04.
  • 0 in reply to ThomasCosby
    Prodigy 130 points
    Thank you, Thomas. I didn't mean the replacement battery will be of the different configuration. Sorry to misguide you by mentioning the change of FCC from 1500 to 7200 mA*h, this is not really our case. The replacement battery will have the same configuration, but I'd like to have a fast way to "RESET" the gauge to the nominal FCC. Is there a way to do it without charge-discharge cycling?
  • 0 in reply to Eldes
    TI__Guru 73830 points
    The gauge requires charge and discharge cycles with rest periods to update Qmax and the Ra table. This is how it "learns" the new battery.