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Original question:

BQ27421-G1: Restoring QMax and Ra after Shutdown

BQ27421-G1: SOH errors and early system shutdown

Rachel Yoder
Prodigy 40 points
Part Number: BQ27421-G1
Other Parts Discussed in Thread: GPCCHEM

Hello,

We are using the BQ27421-G1A for a Li-Ion battery pack (Tenergy 5200mAh 31001) and are experiencing serious issues with the TI part. The battery never reaches the terminate voltage of 3.2V, and I believe therefore is reporting inaccurate Qmax and SOH after just one charge cycle. This is a repeatable issue, and these are new battery packs.

I have a few questions:

- Is the part meant to work for a battery pack consisting of multiple cells in parallel? I assume so, but this is not explicitly called out in any documentation.

- Why would the gauge never reach the set terminate voltage of 3.2V?

- If the part is on a PCB and NOT located near the battery pack, would the temperature read by the part cause significant capacity errors?

- Why is the device accumulating error? Our SOH starts at 92%, then drops to about 83% after the first cycle, and then 75% for the third cycle, etc.

Can someone please help provide some insight into what could be causing out problem? Any help would be greatly appreciated.

  • 0
    TI__Guru* 76230 points
    Hi Rachel

    Did you run the test outlined in our tool gpcchem to determine if this gauge is a good match for your cells. I suspect your issues is coming from the fact that you are using a mismatched chem id. I would advice you run the test with gpcchem as that will let you know if you should be using this gauge or no.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 40 points

    Hi Onyx,

    Thanks for your reply. No we haven't used the gpcchem tool. I currently do not have the correct tools to run this test (the EV2300 is not being recognized by my computer).

    Why would standard Tenergy 18650s cells not be supported by this gauge? If I am able to run this gpcchem test and find out that the chosen battery pack is not compatible, are there any metrics or parameters I can configure in the gauge to minimize the error I previously described?

    I am confused as to why the datasheet advertises this part as usable with 4.2V Li-cobalt based Li-ion batteries, yet our 4.2V Li-cobalt based Li-ion batteries might be incompatible. This potential chemical ID mismatch should be at least mentioned once in the datasheet.

    Thanks,

    Rachel

  • 0 in reply to Rachel Yoder
    TI__Guru* 76230 points
    Hi Rachel

    If you run the test and find out it doesn't work, then you let us know. Is it possible to use a a different flash based gauge in your design? For the ev2300 issue, you should installl the 64bit driver in the link below and see if that helps

    e2e.ti.com/.../EV2300a_5F00_Device_5F00_Driver_5F00_Installer_5F00_Multilanguage.exe'

    Thanks
    Onyx