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BQ24650: Charge Li-ion from lead acid battery pack (charged from solar) : BQ24650 or BQ24610 ?

Benjamin MARCEAU1
Prodigy 30 points
Part Number: BQ24650
Other Parts Discussed in Thread: BQ24610

Hi,

I'm making the charger of a mower robot.

The robot have a 3S li ion pack, the docking station is powered by solar panel and 24V lead acid battery pack to store energy.

Here, my goal is to charge the robot's battery pack with the 24v lead batteries : which is better for charging the li-ion with this configuration, BQ24650 or BQ24610 ? (or other...)

Initially I plan to use 24610, but the MPPT of the 24650 seem to be interested in case of low charged lead acid.

Thanks.

  • 0
    TI__Mastermind 24075 points

    Hi,

      It really depends on whether the lead acid battery will be allowed to discharge below the max charge regulation voltage of your 3S. As both are buck battery charge controllers, they need VCC>SRN by the SLEEP threshold specified in the datasheet. If it is possible for source battery to discharge below this level, then I would recommend using the BQ24650 to regulate the input voltage by decreasing the charge current, so that the source lead acid is not allowed to discharge too far. This allows maximum run time.

    BQ24610 has input current regulation loop, which is useful if using the SYS rail through power path. Are you having an external SYS rail to be powered by adapter while battery is being charged? If not I would recommend BQ24650 for your application.

  • 0 in reply to Kedar Manishankar
    Prodigy 30 points

    Hi,

    The lead battery will not go below the sleep threesold level of the BQxxx the protection circuit of the lead pack will cut the output before.

    During charging I just need to power the microcontroler of the mower and the Wifi module, so, no "big" power consumption at all.

    In this case it is possible to not use the sys rail funcitonnality or its mandatory ? 

    In which case I need to use sys rail / powerpath functionnality ? When they have medium/to big power consumption in addition to charging or as soon as there is something else to power up ?

    Thanks.

  • +1 in reply to Benjamin MARCEAU1
    TI__Mastermind 24075 points

    Hi,

     It is not mandatory to use the power path. There is an application section in the datasheet showing how to connect if powerpath is not needed. BQ24610 would be a better bet if your lead acid UVP kicks in above the max charge regulation of your 3S batteries. It has more configurability over charge current, precharge/termination. I would recommend BQ24610 for you.

  • 0 in reply to Kedar Manishankar
    Prodigy 30 points

    Hi,

    thanks for your advices.

    In which case i MUST use the powerpath function ? Eatch time something need power in addition to charging the 3S ?

  • 0 in reply to Benjamin MARCEAU1
    TI__Mastermind 24075 points

    If you have an external SYSTEM required to be powered by either adapter or battery. If it is high current SYS load, then you would like for it to be powered directly by the adapter whenever adapter is connected, and have SYS powered by BAT whenever adapter is absent. Then you would most likely prefer powerpath. THere is a section in the datasheet that explains the functionality in detail as well.