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Original question:

BQ35100: Li-SOCL2 chemical and measured impedance

BQ35100: Li-SOCL2 chemical ID, measured impedance and too fast falling SOH

Benjamin Meder
Prodigy 35 points
Part Number: BQ35100
Other Parts Discussed in Thread: EV2400, BQSTUDIO

Hi,

I am running into the same issue as Alessandro Berruti. I've got the BQ35100EVM connected to the EV2400. I am also using the SAFT LS 17500 LI-SOCL2 battery but only one bat. After reading this article i also changed the Chem ID to 0x0607. I also used the same steps as Alessandro. My design is right now:

BAT+ -----------|----------------- -------- --|--------- --- -- manual Switch -- --|
SAFT LS 17500 3,6V 20 kOhm 150 Ohm
BAT- -----------|   |   |
  |   |
PACK- ----------------------------- -------- --|--------- --- -------------------------

--|

As you can see we have a constant load of around 0,18 mA and for the manual peak we have 3,4 Volts with an combined Resistance of 145,8 Ohm. Which makes around 23 mA. If I calculate the resistance of my LS17500 it's around 8,36 Ohms.

  1. Put Jumper into the GE-Pull-up
  2. wait until BQStudio recognises the Board and wait until GA Bit is low
  3. Gauge Start
  4. wait a second and wait until GA is high
  5. Press manual Switch for a second
  6. release manual Switch and Gauge Stopp at the same time
  7. wait untill GA Bit is low
  8. check registers in BQStudio.

Checking the Data Graph with the register voltage and scaled R I see my drop > 100 mV.

There i have the SOH_Merit high, sometimes also the SOH_ERR high. Scaled R is around 3-4 Ohm. If I wait a few moments and do the steps 2-8 again (without pulling/putting the jumper out/in) then I get my Scaled R at around 8 Ohms (which is almost the same as my calculated result) but I still get the SOH_MERIT Error. 

Everytime i do the above steps or the second steps without GE-Pull-up my SOH decreases 2 %.

Calibration was made in ACC mode and then changed to EOS Mode.

If I choose a different Lithium Thionyl Chloride Battery, the values in the Table (Data Memory Contents) are changing. So I think I also need the correct Chem ID for my battery to see if my SOH or EOS is calculated correctly.

So what am I doing wrong?

Best regards

Benjamin Meder

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