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Production Cycling for Qmax accuracy in bq20z80A standby backup power application

Alexander Leon
Prodigy 70 points
  • Does Texas Instruments recommend cycling to calibrate Qmax of individual packs in production for standby backup power applications*?
    • Is the pack to pack variation in Qmax/Impedance enough to warrant this procedure for this application?
    • Are there long term benefits to more accurate Qmax pack values than those from the development learning cycles done for creating the golden ROM files?
    • If yes, how many cycles per pack are recommended for this purpose?

* These packs will typically see very few (< 5 per year, possibly 0), discharge cycles of less than two minutes at  3 to 4 A. The packs are nominally 5000 mAh if charged to 8.4V. However, in this application they are only charged to 8.2V to extend battery life. Packs will typically just self-discharge to 85% then recharge back to “100%” (8.2V).  

  • 0
    TI__Guru* 76230 points

    -NO!,  cycling of individual packs will not be necessary. The pack variation in Qmax and impedance will not be significant enough to warrant such except you have old aged packs.

    -There are no significant long term benefits if your cells are not aged. One of the main purposes of learning the resistances is to account for cell aging. The impedance of batteries increase with age.

    -If there is an absolute need to cycle so Qmax is updated and more accurate per pack, then if you are at 100% charge, discharge to 60%, rest for about 5hours or if you see vok bit clear, charge to full, rest for 2hours and check to see that qmax updates. If it doesn't you can repeat the cycle. There will be very little difference in the updated qmax which really makes this unnecessary.

     

    thanks

    Onyx