What's the best way to test a battery module to determine if it's good or bad and needs replaced?

That load tester is designed for 12V batteries. You might have been able to use one of the old fashioned manual ones to test individual modules, but it will probably be very hard to impossible to coerce one of the modern electronic ones to apply an appropriate resistive load for one module.

The easiest way to test would be to get a good OBD2 scanner and use Dr. Prius to read the pack voltages while it is actually in use.

 

The best test is done using a hobby charger. In the menu of the hobby charger there will be an option to perform three D->C cycles. So first set up limits like the minimum acceptable discharge voltage, etc. Once all the limits are set correctly the next step is doing the actual cycling. Ideally you want to get a minimum charge and discharge of say roughly 3000-4000 or so milli amp hours (mah) out of each charge and discharge cycle. The number for the charge mah will always be higher than the discharge mah because of current losses to heat and the battery is never 100% efficient.

Once 3 successful charge /discharge cylces have been performed, then do a final load test using a standard 12v car headlight along with 2 voltmeters. One voltmeter measures the volts and the other one is in series with the headlight to give the current. From that load test the internal resistance of each module can be calculated.

Once all the modules mah capacity has been measured, along with internal resistance for each module, the next step is pairing them up. The goal is to get each pair of modules to have approximately the same internal resistance. So pair the highest internal resistance module with the lowest, etc, such that the pairs all add up to approximately the same number. While pairing them up this way, the secondary goal is to have each pair of modules add up to approximately the same mah capacity.

 

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Try measuring again. How many days/weeks did you leave the HV pack in a resting state before testing? (the longer the better)

What makes you think the current HV battery is bad, or needs replacing?

Do you have a hybrid compatible OBD2 code scanner? (if so, post the codes in this thread)

FYI : you're moderated until you've posted 5 times.

 

That's a pretty comprehensive explanation. I'm getting crappola mileage. I should have done that when I replace a few of the cells. What a pain.

 

Before suspecting the HV battery, check the condition of the air filter and the auxiliary 12V battery.

 

@SFO not sure if you measure internal resistance when rebuilding batteries, but if so, do you have a voltage you manually discharge to for more reliable/reproducible readings?

From what I understand, IR and self-discharge is pretty inconsistent above 80% SOC, but using RC chargers, I don't have a reliable way to bring them down to that (most still at ~7.8v after sitting for a couple weeks).

TIA!