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Chapter 6
Battery Pack Assembly
This chapter discusses inspecting cells prior to assembling into packs and guidelines for creating weld schedules for
A123 cells. This chapter includes the following sections:
•
Incoming Cell Inspection
•
Material Handling and Storage
•
Cell Welding
Incoming Cell Inspection
Cells are checked for excessive self-discharge at the factory before they are released for sale and shipment. A123
still recommends inspecting cells before assembling them into packs. Cells are shipped at approximately 50% SOC,
with a nominal voltage of 3.3V. Test the OCV and compare it to the “Discharge” curve in Figure 21 to determine
how much charge was lost during storage and transport. Typically, A123 cells lose less than 1% per month at 25 °C
temperature. Loss of greater than 3 - 5% per month is cause for concern and those cells should be quarantined for
investigation.
Material Handling and Storage
General Practices
Minimize handling of cells to avoid damaging them. Reject any cell dropped from a height of more than 120 mm. If
a cell is dropped from a height of less than 120 mm, carefully inspect the components for damage and then retest
the OCV and alternating current resistance (ACR). Reject any cells where damage exceeds acceptable limits or of
either OCV or ACR that are not within specified limits. Discard any cells that have been subjected to even a brief
external short circuit. Do not damage the cells in any way that would make them unfit for your intended use.
Storage Conditions
Store and process cells in an environment of 15 °C to 35 °C and less than 75% relative humidity. Keep the cells
under cover and protected them from the elements at all times.
