Page Comparison

Purpose: Validate that our manufacturing procedure yields a module that can function in all realistic discharge scenarios

Tests:

• Module Resistance

  • See Single Cell Testing - Data Processing Guide for a more detailed overview of the intricacies of DCR measurements

  • Connect the eload to the module with a 10A capable connection

  • Measure the voltage of the pack at the busbars using the Keysight DMM

  • Apply a load of 5A with a slew rate of 0.25A/us with an eload, observe the immediate voltage drop of the pack.

    • Over time, chemical processes will cause the voltage to further sag over time. This must not be accounted for in the DCR measurement, so use the first measurement you observe.

  • Use Keysight multimeter to check resistance on terminals of battery module, with integration time of 20ms.

  • Test: Measure module internal resistance. Follow this tutorial: https://www.youtube.com/watch?v=av38iBxcOgQ

  • The cells in 4S8P configuration alone, based off of the measured internal resistance of ~22mOhm/cell, should have an IR of about 11mOhms

  • Cells should not have greater than a 60mV drop when loaded with 5A

  • Information gained: The measured internal resistance should tell use how much resistance is introduced from out spotwelds and busbars (indication of how good our spotwelds are)

• Nominal Current/Balance Test

  • Insert thermistor into the center of the module, in the top third

  • Measure and record the voltage of each cell to at least 1mV precision

  • Connect the eload with a 30A capable connection (2 thick alligator clips in parallel)

  • Apply a 30A load until the module drops below 12V (empty)

    • The temperature rise should be about 10C after 15 mins

  • Recharge the module to 14.5V

  • Measure the voltage of each cell, the imbalance should be the same as before, within 2mV

• High Current Test

  • Our modules are rated for a max discharge of 58.2A

  • Test: Draw 58.2A from module for 10 min

  • Information gained: Temperature rise from max discharge, visual observations of module in case anything unexpected occurs

Test set-up:

Attach module to module connections with M4 bolts, Belville disc springs, and regular washers in this stack up ( Nut - Washer - Busbar - Contact Grease - Busbar - Washer - Springs - Bolt ). Torque the M4 connections to 2.4 N*m.

This way we can see from the tests how good the connections between modules are (IR introduced) and if the module-module connections introduce any issues.