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BQ34Z100-G1: application with no/limited relaxation periods

Matteo Rigamonti
Expert 1170 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ34110, BQ34Z100

Good morning,

we are going to use a battery pack equipped with the BQ34Z100-G1 for a good SOC estimation into a solar luminaire.

In such an application the battery pack is continuously charged and discharged: during day time it is important to maximize the energy collection from the sun through a solar panel for charging the battery, while during the nigh time it is important to guarantee a proper light intensity in the area where the system has bee installed.

So normally there are no relaxation intervals available for the battery because immediately after the sunset the charging phase is disable and light is switched on, while immediately after the sunrise, the charging is enable and light switched off. How the impedance track algorithm can work under such situation?

just in case it would be necessary, we can find a way for leaving the battery pack to relax for a short time. So we would like to ask if that could be necessary/useful and, just in case, which characteristics the relaxation period should have (and some indications about how to set related parameters in BQ34Z100-G1).

Thank you in advance for any suggestion and best regards

Matteo

  • 0
    TI__Mastermind 25955 points
    Hi Matteo,

    Is the bq34z100-g1 already designed in to the pack? If the bq34z100-g1 is a lock, can the battery be sized to ensure full charge (and thereby rest) before dark and/or complete discharge (and thereby rest) prior to sunrise?

    What chemistry is being utilized?

    For multi-chemistry, the bq34110 may be better suited for SOC estimation with this load profile due to the lack of rest periods.

    Sincerely,
    Bryan Kahler
  • 0 in reply to Bryan Kahler
    Expert 1170 points

    Hi Bryan,

    we have the first prototype of the battery pack with BQ34Z100-G1. Just in case, it is still possible (but hard) to discard such a component and switch to the suggested BQ34110.

    Anyway the battery pack is made by NiMH cells (Panasonic BK1100FHU for high temperature). Unfortunately it is not possible to guarantee to reach the full charge condition at any charging cycle (it depends on the sun condition), but in most of cases we hope to fully charge the battery pack. Moreover, normally the complete discharge condition shouldn't be reached (the battery pack has been properly oversized).

    So we can think to add a dedicated rest phase when the full charge condition is reached. Is that enough? How long shold be the rest phase, at minimum? How have we to set BQ34Z100 parameters for assuring a proper working condition?

    Thank you very much for any feedback and best regards

    Matteo

  • 0 in reply to Matteo Rigamonti
    TI__Mastermind 25955 points
    Hi Matteo,

    Unfortunately, the bq34z100-g1 device does not have the fast qmax feature that would allow one rest period, like many of our other gauges. Adding a dedicated rest phase when full charge is reached solves one half of the problem, but qmax will not update without a second rest phase with a DOD drop of at least 37.5% that does not occur in the disqualified voltage range. This would not need to occur every cycle, but would be required occasionally. Depending on the cell and load, resting can take up to 5 hours.

    Moreover, with NiMH, to detect charge termination with -DV/dt, a rate of at least C/5 is required.

    The bq34110 may be the best bet because worst case, the device can be configured as a coulomb counter.

    Sincerely,
    Bryan Kahler