Battery Module Rev 6

Owned by Micah Black
Last updated: Jan 10, 2021
2 min read

So I’ve skipped documentation on a few REVs, but here it goes again with the latest changes.

Main Changes

  • Removed bolt isolation features on the modules and made the battery modules roughly 1cm shorter thanks to a shorter gusset plate. On the prototype battery module, the bolts were tightened to the 2.4 Nm torque spec using a torque wrench. These squished out and did not seem to maintain isolation or torque.

  • Hole sizes for the cells were increased in order to make assembly easier. The prototype had to use clamps to push the cells acetal plates on to the cells. The force of friction between the cells and the holders increases a lot when you have 48 cells vs 1 (this should have been obvious, but good to learn it now).

  • Cell spacing and cooling channels were adjusted to allow for greater cooling and better airflow through the middle to cool the center cells per the Prototype Battery Module Testing Results.

  • An extra cell was added (to make the pack 25P 2S instead of 24P 2S) to make the design easier.

  • Thermistor locations were updated to be on the busbars per ASC inspector’s recommendation - the heat from the cells will heat up the busbars quicker than it will an adjacent cell. So we moved the thermistors to the busbars so that we have greater pack coverage or temperature sensing. The thermistor count was also increased to 4 per module, so 1 thermistor per 12.5 cells, also per ASC recommendation. For student built packs, I definitely agree that there should be more temperature monitoring, but with a more professional pack we could reduce the number of sensors required since better temperature uniformity can be achieved.

  • The busbar voltage taps changed to 2 voltage taps so that we can have a separate balance and measure wires. This way we get better voltage measurements, and can also charge cells individually through 18AWG wires within the module.

  • The gusset plates no longer hold the bolts captive. We will need to insert a socket in the bolt end in order to tighten it. During the assembly process of the prototype, as well as further testing, the plastic deformed before the bolt could be fully torqued.

Module Screenshots