sTEm–at-Work Puzzle #43: Battery Recharge expectations

A major customer of a high performance battery manufacturer has a critical, mission-specific performance expectation from the lithium batteries they purchased. The Quality technician for the manufacturer can only authorize shipment of all of the batteries from each manufactured lot after a statistically valid sampling and subsequent testing of all the batteries in that sample have been performed. If just one of those tested batteries does not at least meet the minimal charge/discharge specifications established by the customer, none of the batteries in that manufactured lot will be shipped to this customer.

Three different charge/discharge tests are performed. A range of expected battery performance as indicated by these three tests is shown in the performance graphs below. One battery, under test, had the following recovery characteristics:

  • It recovered 80% after it was 100% discharged and recharged 500 times
  • It recovered 75% percent after it was 50% discharged and recharged 600 times (and)
  • It was 30% discharged in less than 30 minutes and recovered 70% after 1,200 charge/discharge cycles.
The Tech did not authorize shipment of this lot of batteries to the customer. YES  or NO. Submit your answers below the blog post, or on

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