When I'm checking the cell voltage do I need to have the car running or just have the key in the on position?
On position will give you the unloaded voltage reading. This is helpful but can be deceiving. It would be better if you could see the voltage under load. Gives you a better idea of how they react in real life circumstances.
For example you could see how the block voltages react when power braking. (Parking brake in. Car in drive. Foot on brake. Other foot on gas.) This puts a charging load on he pack. Or drive up a hill in reverse. Coast back to bottom of hill in neutral. Repeat. This puts a discharge load on the pack. Without any charging.
This is slightly old but may help you out. Its how we used to teach testing a battery with techstream: Ready car While you're waiting for the engine to turn off hook up techstream go to HV battery ECU datalist Select PIDs: Battery SOC Delta SOC Batt Block Max Voltage Batt Block Min Voltage Edit list (see pic of button), this will increase the refresh rate Go to Function --> Snapshot Configure Set trigger to Begin Make length as long as possible (60min) Once engine turns off, start recording Put left foot on the brake Shift into reverse Floor accelerator with right foot, this will slowly discharge the battery Deviation b/w max/min blocks tells you the health of the battery. (If it deviates right away (i.e. more than 1v) then the battery is bad and you might as well stop the test.) 1 Wait with both feet on the pedals until the engine starts. You can wait a little bit longer (1-3 minutes past engine start) but you likely already have the data you need. Click stop recording button. Save file. You can reopen it later to make a graph (see examples attached). (Hint: when making the graph, don't forget to adjust max/min voltage parameters to the same range; see menu buttons under graphing area, pic attached; otherwise deviation can be distorted). Shift into park. Examples of new, acceptable, and failing batteries attached. Note that on failing batteries, Delta SOC starts to climb above 20% at the end. Delta SOC defaults to 20%, anything higher is evidence of battery degradation. If you just check Delta SOC on the current datastream, you may already see it creeping up. But when the battery ultimately fails (red triangle, engine revving, no power, etc.) the delta will be 40+. https://photos.app.goo.gl/Re7Ts56vkgAQeEKF9 Hope this is useful to you
