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BQ4050: Optimal Configuration for Solar Charging

Rowan Chase
Prodigy 115 points
Part Number: BQ4050


Hi,

We have an application using the BQ4050 with 4x LPO4 cells, which is solar charged and generally installed in an agricultural environment and therefore subject to extreme temperatures.  While we're aware that the battery performance will be degraded by the conditions, we of course none-the-less wish to achieve the best longevity from the packs as we can.

We've already implemented the temperature safety protections, however we've also been informed by our cell provider that it's good practice to only charge the cells to 90% capacity for our application.

Currently, our devices charging circuitry is providing the battery pack with the voltage and current as specified by the SMBus command 0x14 ChargingCurrent() and 0x15 ChargingVoltage(), which according to the documentation return the desired charging current and voltage respectively.

Is there a configuration of the BQ4050 designed for floating the charge at 90% (or some other set point below 100%), which will be reflected in these two registers?  ie. the registers will report 0A and 0V once the desired SOC has been achieved.

Thanks,

Rowan.

  • 0
    TI__Guru** 105870 points

    Hello Rowan,

    You can check the TRM section 4.3.1 RelativeStateofCharge() Range

    That may be what you are looking for instead of using voltage levels for charging.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 115 points

    Hi Wyatt,

    Thank you very much, that does appear to be what I was looking for.

    Given we'll be floating at this SOC threshold and not hitting 100% in normal use, we'll not be charge terminating nor hitting the lower voltage thresholds.  My experience is that the BQ series tend to loose track of the actual SOC over time if they are not regularly exposed to a full charge cycle.  Is there a recommendation, when using the RelativeStateOfCharge mode with regards to this issue?  eg. should we allow the battery to perform a full charge cycle every so often?

    Thanks for you help,

    Rowan.