Prius HV battery replacement

This may be old hat to some, but I figured a few of you might get something out of this! One of our regulars brings their Prius in with the master warning on (the big red triangle), stating that it seems like the HV battery isn't charging as it used to. Codes first, of course:



Welp, that's pretty straightforward. :lol: The flow chart for this code is laughably short, ending with replacing the Battery ECU, or the HV battery pack. No other troubleshooting information is given. :blink:

Not being a parts changer, I want to have a bit more to go on, so I do some research. Turns out that the Battery ECU is watching the voltage of the individual battery blocks (14 in all), looking for any that aren't keeping pace. Again, no specification is given, but the number I find to use is any pack that varies .5V or more from the rest of the battery blocks. Sort of like secondary ignition waveforms, it's a case of 'one of these things is not like the others'. I can do that.

I grab the battery data and go for a drive. Check out the ScanShare link if you want, but I can fast track it for you:

www.scanshare.io/Share/YFihLhvh7E6N9ftJ1_779g



All the graphs look identical, sure, but check out the current reading and the min/max on the left. Block #2 is low, and consistently shows the lowest voltage of all 14 blocks. This is what the ECU doesn't like!

The customer goes for battery replacement, which requires removing most of the rear interior panels:



There it is! Gloves are required for handing the main cable connections. Trying not to let the smoke out of Tyler today.

One new battery later, and I go for another drive.



Looking much better! Some variances, sure, but no real slackers. The minimum and maximum voltages are within .5V of each other, as the guideline suggested they should be. No codes, ECU is happy, which means I'm happy.

Sweet ............. nice win.