BQ35100: Li-SOCL2 chemical and measured impedance

hi Alessandro,
We will get you a response before thursday.
thanks
Onyx

Alessandro,

Thank you for your interest in the bq35100. I have a question about your procedure. You say "wait until the voltage reach a stable value". I am unsure what you mean by this. The expected procedure for EOS Mode is added/changed steps in yellow

• GE asserted 
• gauge start command
• wait for [GA] = 1
• discharge @ 50mA for x time (Voltage Drop during pulse > 100mV)
• gauge stop command
• wait R Data Seconds.... Wait until [GDONE] = 1
• GE de-asserted

1) You want to remove the Dsg load then send the gauge stop command. The gauge is expecting a pulse load in order to correctly identify the impedance of the cell. 

2) SOH max delta is there to protect you from SOH dropping so rapidly on 1 high reading. I would recommend leaving this value to 2. 

3) Yes the gauge expects the GE pin to be toggled between gauge start and gauge stop sequences.

4) The default values in the gauge are for the LS17500.  So there is no need to update the chemistry.

4) Please make sure calibration is done in ACC mode (GMSEL 0,0). Then changes to EOS mode (GMSEL 1,0).

Let me know if this doesn't help or if you have more questions. 

Thanks,

Eric Vos

Hi Eric, thank you for your reply,
the steps that you highlighted are satisfied by my application also if I didn't explain it in an appropriate way.
Regarding the list:
1) ok
2) for every value that I put in SOH max delta, at the end of computation, the drop of the SOH is just this value. If I set 2 every time the drop is 2.
3) ok
4) what do you mean with default value? Which chem ID? 0607?
5) the calibration is done in ACC mode.

Thank you

I still need help with this problem, I follow all the steps, but the SOH_MERIT bit is set all the time and (if set to 2%) after 50 reads the battery SOH drops to 0%. I attach two screenshot of bqstudio.

Alessandro,

SOH_MERRIT is better named EOS_MERRIT. It comes on when there is a problem in the EOS Impedance calculation. What this means is that during the measurement a voltage was seen that was higher than the initial OCV measurement gethered at the time GE was put high. 

If the cell is not rested the voltage will increase between GE high and Gauge Start. This will cause an error. For future tests please ensure a more rested battery and less time between GE high and Gauge Start CMD. Also be sure the send the gauge stop immediately after the load is removed. 

Let me know if this doesn't help. 

Thanks,

Eric Vos

Hi Eric,

I thought SOH MERIT's claim meant that the SOH calculation had been limited by "maximum health delta status", in fact EOS_BAD_OCV means "that during the measurement a voltage was seen that was higher than the initial OCV measurement gethered at the time GE was put high".

From my screenshot is possible to see that the SOH_MERIT is set, instead EOS_BAD_OCV is clear.

From the last tests, the measured impedence is about 2000/21000ohm. But the computation of the SOH is limited all the time.

In the previous reply, you said "The default values in the gauge are for the LS17500.  So there is no need to update the chemistry.", what do you mean with default value? 0x0606, 0x0607 or other?

Thank you,

Alessandro