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BQ21061: Not charging battery

silomilo
Intellectual 320 points
Part Number: BQ21061
Other Parts Discussed in Thread: BQ25155

We recently upgraded our charging solution to the BQ21061 on our product and I'm having some difficulty getting it to charge a battery. If I connect a discharged battery STAT0 = 0x01 and that's the only bit set in the STAT/FLAG registers. I've tried toggling VIN (USB) and only see the pgood bit toggle. No change to the charge registers

I've tried hot swapping the battery too and if I remove the battery STAT0 will show 0x21 or 0x41 and when I plug the battery back in goes back to 0x01 so it seems like the charge SM is running but refusing to charge my battery.

*Note: I've tried this with 2 Li-Ion batteries (3.5V and 4.0V) and get the same result

All the registers are their default values.

BQ21061 Register Dump
Register 0x00 = 0x01
Register 0x01 = 0x00
Register 0x02 = 0x00
Register 0x03 = 0x00
Register 0x04 = 0x00
Register 0x05 = 0x00
Register 0x06 = 0x00
Register 0x07 = 0x00
Register 0x08 = 0x00
Register 0x09 = 0x71
Register 0x0a = 0x00
Register 0x12 = 0x3c
Register 0x13 = 0x08
Register 0x14 = 0x02
Register 0x15 = 0x14
Register 0x16 = 0x00
Register 0x17 = 0x82
Register 0x18 = 0xc2
Register 0x19 = 0x06
Register 0x1d = 0xb0
Register 0x30 = 0x2a
Register 0x35 = 0x10
Register 0x36 = 0x00
Register 0x37 = 0x40
Register 0x61 = 0x34
Register 0x62 = 0x7c
Register 0x63 = 0x6d
Register 0x64 = 0x38
Register 0x65 = 0x27
Register 0x6f = 0x3a

  • 0
    TI__Mastermind 21590 points

    Hello,

    How many volts do you measure on TS?

    How many volts do you measure on IN, PMID, VDD, LDO?

  • 0 in reply to Raheem
    Intellectual 320 points

    Hi Raheem, here are my measurements. Please advise.

    VBAT = 4.1V

    TS = 0 ~ 400mV (I see pulses approximately 25ms wide at 400mV every 250ms)

    IN = 5V

    PMID = 4.5V

    VDD = 1.8V

    LDO = 2.6V

  • 0 in reply to silomilo
    Intellectual 320 points

    Another quick update, in case it provides some useful information. 

    I left one of my units in this non-charging state (stat0=0x01) powered overnight and in the morning it was showing 0x21 (charge complete). At that point I was able to power cycle IN and see the device enter 0x41 (CV) and progress to 0x21 (done) again. I cycled in a few times and everything appeared to be working.

    However, then I decided to try with some batteries of different charge levels and the old behaviour returned after swapping batteries. When I return to the original one which was working in the above testing the unit seems to work again. That being said the unit has had issues with both batteries in the past, and both batteries are between 4.1 and 4.2V.

    Is there some sort of long delay when initially powered where the BQ21061 needs to perform some checks? I've let the unit sit for 10-15 minutes now and it's still in 0x01.

  • 0 in reply to silomilo
    Intellectual 320 points

    I think the issue may have been that I assumed that IINLIM_ACTIVE_STAT would be set while the device is in "constant current" mode (ie. trickle / fast charge). Upon further inspection it seems like the BQ21061 is in fact charging the battery, however unless I'm mistaken there is no positive indication of charge enabled.

    Is there anyway to tell when the device is charging the battery in pre-charge or fast charge?

  • 0 in reply to silomilo
    TI__Mastermind 21590 points

    Hello,

    IINLIM_ACTIVE_STAT will be set only if the device is actively limiting the input current which is not always the case. Are you able to place a current probe on VBAT to measure the charge current to know if the battery is actually being charged or not?

  • 0 in reply to Raheem
    Intellectual 320 points

    It's not possible to measure battery current but I was able to see the VBAT increase when I change the current range from 1.25mA to 2.5mA so it seems that the battery is in fact charging. However, I would still really like to have a way to confirm that the battery is in fact charging.

    Is there any way to read from the BQ21061 that it is charging the battery?

  • 0 in reply to silomilo
    TI__Mastermind 21590 points

    Hello,

    The BQ21061 does not have this feature .However, the BQ25155 has an integrated ADC which allows you to measure the charge current.

    You can take a look at the VIN power status and charge done in STAT0 to get a sense of charging. Note that the bits dont change if charging is disabled.