I need to confirm when the ECU would throw a code on a bad battery

There are other things besides resting voltage that could make a Prius throw a HV battery pack DTC code.

Are you currently experiencing a DTC?

 

JC,

I'm sure you've read Art's "Predictive Failure Analysis" but here's the link anyway:

Predictive battery failure analysis for the Prius Hybrid

There is a "standard" min/max variation of .3v that gets thrown around here on PC and I think it's assumed this will throw up the triangle. I think it may, but I also think it has to be recorded by the hybrid battery ecu for an extended period. Of course I have no idea what that time period is but I'm quite sure min/max variation can and does vary at .3 and above on many, many batteries without any code or driveability issues. I believe 1.2 volts, or more, variation is the software's "instant triangle and rev up the fan" threshold.

You can watch mini VCI while driving (somebody else driving, of course) and see these variations in older, yet still working fine, batteries. My daughter's 07 (151k) has been in the .3-.4 range for over a year now and runs as good as ever. I tested an 08 with 155k this spring and it showed real-time .4-.5 many times during the drive. The guy traded it on a 2015 but that car never even showed a check engine light in it's 155k life.

It seems that many of the battery failures we see accompanied by snapshot data here on PC show the big variation of 1.2 or more. Thus my thinking that anything less than 1.2 can and does happen as we motor on in ignorant bliss. Art's article supports this, too. I'm with you though, watching any more than .2 variation wigs me out! My 2010 is still super tight, less than .2, thankfully. Now one of the resident electrical wizards can set me straight on all this.

Mike..

 

The Toyota repair manual indicates that the conditions under which the traction battery ECU will log a DTC (P3011 - P3024, which corresponds to the 14 module pairs which might have an abnormal voltage) is Toyota intellectual property. However, the manual also goes on to say that if all module pair voltage differences are more than 0.3V, then replace the battery ECU. The test compares module pair 1 with 2, 3 with 4, 5 with 6, etc.

I suppose the thinking is that if all of the module pair voltage measurements are so far off, then the ECU is more likely to be at fault than all 28 modules.

The inference then, is that if one or two voltage differences between module pairs are greater than 0.3V, that the traction battery ECU may decide to declare a module pair at fault. However that is not specifically stated.