Load Testing

I have no idea how to do this. From what I read, modules that are on the threshold of being unusable can appear as though the have an appropriate voltage (as explained in the previous post), but as soon as they’re put under load (e.g. trying to drive the electric motor) the voltage drops disproportionately. So the idea is that checking the voltage of the modules gets the low hanging fruit, load testing the modules gets most of the rest of them.

Given that I have no idea how to do this, what I understood the be the process is as follows:

  1. Determine an appropriate load – one site mentioned (capacity * voltage)/5 as a good range. For an individual Prius module, that would be (6.5 Ah * 7.2 V)/5 ~= 9.4 watts. Something around there would be useful, but doesn’t need to be exact, I imagine 5 watts would do the trick as well.
  2. Check the voltage of the cell with nothing attached
  3. Apply the load
  4. Check the voltage of the cell under load

That’s about it. I skipped this step, as I had the battery chargers ready to go and figured they would be the best measure of module health. The risk, of course, being that I may waste precious time cycling modules that are no good and could have been excluded by virtue of the load test. So far as I understand it, the load test will not yield anything the discharge cycle on the battery charger wouldn’t also tell you, as that’s basically exactly what it’s doing.

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