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BQ27GDK000EVM: GDK general questions

leinho
Expert 1230 points

Part Number: BQ27GDK000EVM

Hello,

I am looking into the GDK as a solution for the calculation of the CHEMId for my Lithium Ion Battery (Charging Voltage = 4.2 V). This tool is great because compared to using a EV2400 we can control the charger and load using a script from bqStudio. This means, after everything is setup, we can leave the characterization running. 

After looking at the documentation, I have the following questions:

1- In my device, I am planning to use a BQ24232 (linear charger) and this GDK has a switched mode charger. Would using the charger provided by GDK make a difference in the estimation of CHEMID? I mean, differences regarding accuracy compared to when the battery is in our device. I would say this can be solved with a learning cycle in the device but I am not sure.  

2- How is it normally used to measure the temperature of the battery for the CHEMID? Does the battery need to be placed in a specific position in order to use the internal sensor of the on board gauge? I think I would be ok with using the internal gauge but I would like the temperature reading to be accurate enough for GPCCHEM.

3- The battery has an NTC so I thought I could also use the bq27520evm (has an NTC pin) and connect it to the GDK. By the way, if I can not use a ROM based gauge, I would use this gauge. One thing I did not understand for this gauge is figure 6 of SLUU426B. Do I need a 3.6V power supply or is the figure wrong?

4- Should I calibrate the gauge before doing the characterization of the battery?

Thanks for your help!

  • 0
    TI__Guru* 76230 points
    1. The onboard charger on the GDK suffices for chem id identification and learning cycle. You do not need to use yours. Nothing gets affected.
    2. Use the thermistor on the bq27520. Place it on the battery to measure battery temperature not ambient
    3. You can also use the battery ntc in place of the thermistor on the gauge. It will conncet just like the thermistor on the gauge board. in figure 6, that should be your battery. The power supply in figure 6 was just to emulate a battery. pls see gdk user guide or quick start guide on how to connect an external evm with the gdk
    4. Yes, that is recommended.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Expert 1230 points

    Thanks Onyx for your clarification. Could you please help with these additional but related questions?

    Regarding calibration, I saw in the bq27520 EVM User Guide how to do it and it looks clear. I have an Extech Multimeter (EX530) that is calibrated. In order to measure temperature, I am planning to buy a Type K Thermocouple so I can also use this calibrated multimeter to measure the temperature of the pack. Would this be a reasonable choice in terms of accuracy?

    Regarding initial learning and also calibration, should not we also do this in the end device using bqStudio and maybe this GDK or an EV2400?

    By initial learning, I mean the initial values of QMax and  Resistance profile to be used in case we select a ROM type gauge.

    Thanks for you help.

  • 0 in reply to leinho
    TI__Guru* 76230 points
    Leinho,

    For temperature calibration, yes that is a reasonable choice.
    you can do it on your end device, but for convinience most people do it on an EVM and then program the golden file gotten from that on the end unit. The gauge will learn each individual battery in the field.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Expert 1230 points
    Ok,that makes sense. I think this applies to flash based type but I undertand what you mean. This EVMs are really convenient.

    Thanks!
  • 0 in reply to leinho
    Expert 1230 points
    Hi Onyx,

    I was wondering if the GDK would be able to take the temperature reading from the external gauge when we log the file using the script?
    How would this be configured?

    Thanks.
  • 0 in reply to leinho
    TI__Guru* 76230 points
    Leinho,

    The goal is to achieve learning here correct? or chem id identification. what you need for both is the gauges measurement for this which bqstudio would logs. Also, the script is not really needed for gdk. You can configure and set it up using the gdk plug in in bqstudio. You can set relax time, charge current, discharge current, taper conditions etc using the gui and also set the number of cycles you want

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Expert 1230 points
    Yes, chem id identification first and then later on learning cycle. I just wanted to confirm what temp sensor the Script would use (section 6.8 of SLUUAO1A). It looks like there are 3 possile options: onboard, external transistor connected to J1 and gauge's temperature but I could not find a way to tell the script to use the gauge's one. If the script is going to take the voltage, temperature and current from the gauge, that's going to be perfect. I was confused a little bit about the other available temp sensors.
  • 0 in reply to leinho
    TI__Guru* 76230 points
    I really haven't played with the scripting. I always use the gui. The gauge uses its own thermistor to ensure learning completes. The GDK has its own voltage current and temp measurement and that is what is used for the control scheme. The gauge on uses it's own voltage current and temp measurements to ensure learning completes.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Expert 1230 points
    How do you use the GUI to get CHEM ID? I thought the only way would be writing a simple script (charge, relax, discharge, relax)
  • 0 in reply to leinho
    TI__Guru* 76230 points

    when you connect the gdk and start bqstudio, click the gdk tab. The manual conntrol as seen below will allow you set charge, discharge and relaxation and the no of cycles which is all you need for both chem id identification and learning cycle.

    See the quick start guide of the gdk for additional details.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Expert 1230 points
    Ah, ok. But that's not automatic and that's why I prefer the script. We do not have people 24 hours able to change modes in time. I will have to try then what temperature is used when the script generates the log file. Can you log also using the manual control?
  • 0 in reply to leinho
    TI__Guru* 76230 points
    sorry, there is a thirdtab that was not captured in the snippet that is for automatic control.

    There are three tabs, manual, automatic and scriptable control
    thanks