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Li-Ion Charger w/ Solar and DC Power Input

George Ioakimedes
Genius 4950 points
Other Parts Discussed in Thread: BQ24650, TPS2121

I'm doing some initial research for a project. The design could use either single cell or 3-4S Li-Ion battery. The cells would be relatively small (less than 1Ah) but the power source can switch between solar OR ~20VDC in. The design will consume between 300-500mA (only when activating WiFi). I could use I2C for configuration if needed but that's not preferred.

I'm having trouble narrowing down the part choices so I thought I would ask.

Thanks in advance,

George

  • 0
    TI__Mastermind 25800 points

    Hey George,

    I would recommend something like the BQ24650, which as an external MPPT pin which will attempt to regulate at a fixed voltage. For a number of solar panels, you can estimate the MPP as a fixed % of the VOC, somewhere between 70-80%. 

    With this charger, you can regulate to this threshold using a resistor divider connected to the MPPSET pin of the charger. This is also a standalone charger, so most settings can be programmed using 1 or 2 resistors. 

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Genius 4950 points

    Hi Joel,

    Thanks for the suggestion, the BQ24650 does look nice but it doesn't address my application when the input power can come from a DC power source. In an ideal world the product can be powered from DC (if it's available), solar (if it's available), or rely on the battery if no input power source is available.

    Would you mind taking another look for me please.

    Thanks,

    George

  • 0 in reply to George Ioakimedes
    TI__Mastermind 25800 points

    Hey George,

    For this multi-cell, multi-input source type of application, specifically with solar panel input and the desire to have it be a standalone device, the BQ24650 will be the best option. 

    The BQ24650 is our only standalone, multi-cell device that can regulate the input voltage which is what you will need for a solar input. 

    Now because you want to have a secondary input, I would recommend adding a front end device like the TPS2121 power mux to select between input source. 

    And to solve your power selection (input vs. battery), I have linked another e2e post regarding adding power path selection to the BQ24650 with discrete components.

    https://e2e.ti.com/support/power-management/f/196/t/756067?tisearch=e2e-quicksearch&keymatch=power%20path%20bq24650

    Regards,

    Joel H