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Original question:

BQ25171-Q1: application questions

BQ25171-Q1: application questions

Slava Prokopii
Intellectual 2065 points
Part Number: BQ25171-Q1

Hello team.

Customer finished the evaluation of production variant of BQ25171-Q1   -  BQ25171QWDRCRQ1.

The evaluation results are the same as were received on preproduction samples ( this is completely described in initial thread).

If customer sets the charge limit to 4.2V, then charging process stops while batteries are not fully charged.

If customer increases the number of cells in BQ setup only, but leaves the same amount of cells on the board (BQ setup -1), then BQ overruns the timer and indicates an error.

So the question is:

is it possible to use BQ25171-Q1 to charge NiMH-cells completely without cheating the BQ configuration and without getting an error?

Thank you.

  • 0
    TI__Mastermind 19195 points

    Hello Slava,

    Slava Prokopii said:

    If customer increases the number of cells in BQ setup only, but leaves the same amount of cells on the board (BQ setup -1), then BQ overruns the timer and indicates an error.

    Can you clarify what you mean here? The number of cells you are charging should match the cell count referenced in table 7-2. For the "error", what are the STAT1/STAT2 values you are seeing?

    Slava Prokopii said:

    If customer sets the charge limit to 4.2V, then charging process stops while batteries are not fully charged.

    When setting for NiMH configuration there is no CV phase, the max charging voltage for the cells is ~1.7V * # of cells. You may want to check you have the correct resistor values set in case you have configured the device for Li-ion instead.

    Slava Prokopii said:

    is it possible to use BQ25171-Q1 to charge NiMH-cells completely without cheating the BQ configuration and without getting an error?

    Is there any load on the batteries during charge that would prevent them getting the full current? Can you please provide an IVT log showing a full charge cycle. 

    Thanks,

    Nick

  • 0 in reply to Nick Brylski
    TI__Intellectual 2065 points

    Hello Nick.

    Customer evaluates our board BQ25171EVB together with 43AAA600L battery, no any additional loads are used.

    Here is the setup and charging process description: 

    Settings of the BQ25171 are:CHM_TMR pin resistor value is 27 KOhm, so the timer is set for 6 hr for NiMH type.

    VSET pin resistor value is 18 KOhm and we connect 3-cell NiMH battery 43AAA600L.

    Charge process started at 9:40 and finished at 11:17. So the duration is just 1 hour and 37 minutes and the battery hasn't full charge: discharging has shown only 267 mA*h that is twice less of nominal capacity!

    When the charging finished we saw the values STAT1/STAT2 are high.

    Battery Battery number Vpws4602 (v) Ipws4602 (mA) Vin_bat20jfilm Vin_bq25171 (v) Vout_bq25171 (v) Vset_bq25171 (kR) Iset_bq25171 (mA) CHM_TMR_bq25171 (kR) STAT[] Time Note
    43AAA600L-3S1P-FT 1 5,00 72,40 Set 5,00 0,00 18 72 27 rec fault 9:40 battery disconnected
    43AAA600L-3S1P-FT 1 5,00 72,40 Set 5,00 3,80 18 72 27 norm charge 9:45 battery connected
    43AAA600L-3S1P-FT 1 5,00 72,40 Set 5,00 3,96 18 72 27 norm charge 10:00 battery connected
    43AAA600L-3S1P-FT 1 5,00 72,40 Set 5,00 4,10 18 72 27 norm charge 10:30 battery connected
    43AAA600L-3S1P-FT 1 5,00 72,40 Set 5,00 4,17 18 72 27 norm charge 11:00 battery connected
    43AAA600L-3S1P-FT 1 5,00 72,40 Set 5,00 4,16 18 72 27 сharge completed 11:17 battery connected
  • 0 in reply to Slava Prokopii
    TI__Mastermind 19195 points

    Hello Slava,

    You may try cycling the input power and trying the charge cycle again. With your resistor setting device should not stop charging at 4.2V. 

    I tested your setting in the lab and was able to charge all the way up to 1.7*3 = 5.1V, (unable to replicate what you are seeing) . If you are seeing the charge current taper at 4.2V this may be the case.

    Can you confirm the resistor values are correct with DMM? You may also try testing the charge with a sourcemeter, what is the charging current when OUT <3V and >4.2V. 

    It would also be good to know how many units you are seeing this issue on.

    Thanks,

    Nick