BQ35100: Primary battery gauging

Hi Christian,

The workaround in your case would be one of two options which are as follows
Option 1:
When the battery is drained and you remove the old battery and then insert a new one, you need send the new battery command to get the SOH to go back to 100%, then you toggle the GE pin several times to force an OCV measurement and change the SOH by more than the State of health max delta. You can also use the reset command instead of toggling the GE pin. You do this until the SOH stabizes. Make sure the battery isn't under load when sending the Reset command or toggling the GE pin

Option 2
After the new battery command is sent, you change the State of health max delta to a large value like 80%, make sure your battery isn't under load, and then send the reset command or toggle the GE pin. The gauge will take an OCV measurement and corrent the value of the SOH to the right value, then you change the State of health max delta back to "2" to limit how much the SOH can change. The purpose of the limit on there is to prevent a loaded battery from reporting 0 SoH or a wrong SOH if under load.. it is preferable for SOH measurements to be taken under open circuit conditions.


thanks
Onyx

Thank you mr. Ahiakwo. In the next few days I will try your solutions.

Best regards.

Christian.

I have tried the option 1 and everithing seems to be ok.
Except one thing: when I read the current value (2 bytes from 0x0C) I read always 0mA.
Temperature and voltage are ok.
Why I can't read the current value? For my application this information is very important.
Thank you in advance.
Christian.

Hi Christian,
Are you sure you are drawing current from the battery, because if you are not it will report 0mA. Pls double check.
thanks
Onyx

Hi Onyx,
Yes I have double checked. I read 0mA even if I draw from battery from 3mA to 300mA.
Now I'm using bq35100 in STATE-OF-HEALTH mode, because I have a LiMnO2 battery (Energizer CR123 3V).
I have read in datasheet that in this mode the chip measure voltage and temperature, but can I read load current also?
It seems I can read current values only in ACCUMULATOR mode and in END-OF-SERVICE mode. Is that correct?
If yes, I need to change battery chemistry or there is another way?
In my application I need battery SOH, voltage, current and temperature....
Thank you in advance.
Christian.

Hi Christian,
Let me double check with the systems engineer if current can be read in SOH mode. My thought is that the chip should allow this functionality even if it is not use for anything, so i would be surprised if it doesn't allow current measurement. On the other hand, they may have turned off current measurement to reduce the overall current draw of the chip in SOH mode. In the meanwhile, can you verify that you are able to measure current in accumulator and eos mode?

thanks
Onyx

Hi Onyx,

Yes, I can read current values when in ACCUMULATOR and EOS mode.

When switch to SOH mode the current register value seems to be freezed to the last value and does not change anymore.

Do you think it is possible to have a specific version of firmware that leave powered the current measure circuitry when in SOH mode?

Best regards.

Christian.

Hi Christian,
I just verified from the system engineer that current measurement was turned off in SOH mode. We will consider an option of turning it on in a later firmware version in the future. For now you will have to use either the accumulator mode or EOS mode. I recommend accumulator mode.

thanks
Onyx