• State TI Thinks Resolved
  • Locked Locked
  • Replies 11 replies
  • Answers 6 answers
  • Subscribers 62 subscribers
  • Views 199 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ27510: Question Regarding getting the ChemID for a Li-Ion Battery

Ahmed Sabry
Prodigy 150 points
Part Number: BQ27510
Other Parts Discussed in Thread: BQSTUDIO, GPCCHEM

Dear All,

We used the BQStudio to get the ChemID for our Li-ion Battery, we are using the BQ27510EVM with EV4200 to gather the log as required on the document http://ti.com/lit/slva725

We followed these steps:

  • Started with an empty Battery.
  • Charging the battery for 4 Hours (Without a load until the current dropped from 512mA to 0mA suddenly, and the voltage increased from 4.23V to 4.9 which is the charger output voltage)
  • Relaxing for 2.19 Hours (Without a load)
  • Discharging the battery for 7.6 Hours (With a load- the average current ranges between 450:550mA)
  • Relaxing for 6.7 Hours

Taking into consideration that the battery capacity is 4000mAh, and charging voltage is 4.2V, discharging voltage is 3V (This information are listed on the datasheet of the battery)

The data log is available within this link DataLog

So we have some questions,

  1. Did we follow the instruction correctly since it's not clear if we need a load during relaxation and charging or not?
  2. During discharging, when do we consider that the discharging is completed, is it when we reach the termination voltage (3V) or when no current is drawn by the load (0A)?

Talking into consideration that we used the Gauging Parameter Calculator, and we got the following output

0 0 0 0 0
Warning: First OCVpoint has non-zero current I= 0.915 Please make sure you have a 2 hr relaxation period before the beginning of discharge. 0 0 0 0
Warning: Last OCVpoint has non-zero current I= 0.92 Please make sure you have a 5 hr relaxation period after the end of discharge. 0 0 0 0
Warning: Discharge rate is too high. High rate reduces ID detection accuracy 10 hr rate is recomeended. Total discharge time is less than 5 hrs t_hrs= -0.00138888888888889 0 0
Error: No discharge portion found Make sure discaharge current is negative N_points= 2 0 0

Looking forward to your reply.

  • 0
    TI__Guru 57747 points

    Hello Ahmed,

    Chem ID matching requires using bare cells with no protectors.The voltages are measure at the cell. So when current drops to 0 during charging, the cell voltage would fall instead of rising to charger voltage.

  • 0 in reply to Shirish
    Prodigy 150 points

    Dear Shirish, 

    many thanks for your reply.

    We used a bare cell without any protection, we got the best ChemID but with the following warning

    Warning: Max R deviation ratio can not be checked because discharge hr-rate is above 12.  Hr rate = 19.2381080635804

    we used a discharging current about (C/20) which is approximately equal to optimal discharging current during our application.

    My question here, is using this value of current is not sufficient for getting the proper chemID?

    another question please related to this point, we are getting the ChemID to start its learning cycle, is the value of (C/20) shall be sufficient during the discharging phase of the learning cycle?

    looking forward to your reply.

  • 0 in reply to Ahmed Sabry
    TI__Guru 57747 points

    Hello Ahmed,

    The GPCCHEM tool has an instruction manual. This process is independent of your system/application. For Li-ion batteries it requires a C/10 discharge rate. Charge termination current must be C/100 or less.

  • 0 in reply to Shirish
    Prodigy 150 points

    Hello Shirish, 

    thanks for clarification,

    But regarding the learning cycle, is it sufficient to use the C/20 during its discharging phase?

  • 0 in reply to Ahmed Sabry
    TI__Guru 57747 points

    Hello Ahmed,

    No. Learning cycle load must be between C/5 and C/10. See www.ti.com/.../slua903.pdf

  • 0 in reply to Shirish
    Prodigy 150 points

    Hello Shirish, 

    I have a question here, as I mentioned before the optimum discharging current for our application is approximately C/20,

    Is it okay to use another load for performing the learning cycle and then use the info exported from the golden file with our application?

     Many thanks for your consideration.

  • 0 in reply to Ahmed Sabry
    TI__Guru 57747 points

    Yes, that is the correct procedure.

  • 0 in reply to Shirish
    Prodigy 150 points

    Hello Shirish, 

    I have two questions please, 

    1) Regarding the acquiring of the ChemID, does it matters if the Thermistor is connected to the EVM or not? will it affect the results?

    2) Regarding the learning cycle of the battery, is it okay to use the battery without its protection circuit, I mean will it differs if use the bare call instead of connecting the cell with its protector?

    Many thanks in advance.

  • 0 in reply to Ahmed Sabry
    TI__Guru 57747 points

    Hello Ahmed,

    1. It is ok to have the thermistor connected to the EVM as specified in the application section.

    2. For learning cycle, use the battery with its protection circuit. The protection circuit must be removed only for Chem ID matching, it does not need to be removed for any other operations.

  • 0 in reply to Shirish
    Prodigy 150 points

    Dear Shirish, 

    I have a quick question regarding acquiring the chemID of the battery, during the phase of charging, is It mandatory to use the CC/CV method for charging the battery? 

  • 0 in reply to Ahmed Sabry
    TI__Guru 57747 points

    Hello Ahmed,

    CC/CV is the standard method to charge. Using non-standard methods could result in data that is misunderstood by the tool. I would recommend using CC/CV method for charging in order to get good results from the tool.