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BQ76925: Monitor 4s30p 18650 cell battery pack

SWAROOP R SADARJOSHI
Intellectual 725 points
Part Number: BQ76925
Other Parts Discussed in Thread: BQ24650, ,

My requirements: charge (at 0.5C) Li-ion battery pack using a solar panel, and discharge (at 0.3C) the battery pack with a load.
A suitable cost effective solution is required!

Battery pack: 4s30p configuration of 18650 cells of 1000mAh capacity each.

Short listed IC for solar charge controller with MPPT:

BQ24650

but it has maximum charge current = 10A, I need at least 15A charge current! (charging at 0.5C)

1. Is it possible to employ two BQ24650 to meet the demand of 15A charge current?

2. Dose the BQ24650 support simultaneous charge (using solar panel) and discharge (supplying a DC load) of Li-ion battery pack?


For battery monitoring (4s30p 18650 cell pack):

Shortlisted ICs:

BQ76925

3. Is this battery monitoring ICs suitable to monitor 4s30p battery pack, with majority of protection features?

4. How is behavior of the battery monitor IC when it is monitoring a 4s30p configuration of 18650 cells?

5. What could be the best suitable microcontroller in MSP430G2xx2 series (maximum features) for the above battery monitoring IC?

6. The selected MSP430G2xx2 should be able to communicate to a GSM module.

My application is not automotive

Kindly guide me in this regard.


Thanks and regards.

  • 0
    TI__Guru 54715 points

    Hi Swaroop,
    on the bq76925:
    3. The bq76925 can work with 4 cells and help measuring cell voltages and pack current with an appropriate sense resistor. 1 thermistor is supported for pack temperature, that one point may not provide much temperature information with 120 cells. The bq76925 has a current comparator to alert the MCU. The bq76925 does not implement protections, the MCU would do that based on the readings it obtains from the bq76925 and its algorithm.
    4. Based on command from the MCU the bq76925 will provide a scaled cell voltage to the MCU for measurement. It will also provide a scaled/shifted value for each side of the sense resistor. The thermistor can be energized and the current comparator may be configuired if desired.
    5, 6. The MSP430 experts should be able to provide better recommendations. In general you will want a device with enough resolution on 3 or 4 ADC channels for the quality of the measurement you want to make. It will need I2C for controlling the bq76925 and whatever interface is selected for the GSM module. Of course you need enough code space for your application. I believe memory became tight in the bq76925EVM with some of the functions expected beyond the demo code.  With the 120 cells you may want the MCU to implement more temperature measurement points in the cell array.

  • 0 in reply to WM5295
    Intellectual 725 points
    Thanks for replying WM5295!

    I will consider all the suggestions that you have put forward.

    I shall consult on e2e if I have any queries.

    Thanks and regards!