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Does your scan tool give you live data of the HP battery ECU? There are 14 blocks you know what the voltages of each one of these blocks? What year is this Prius? Does your code reader give you sub- information codes?
Do you have the ability on your scan tool to monitor the HV battery voltage per cellblock while it is readied on?
Here's the problem. The C codes that you have artistically malfunction codes and other subsystems because you have a malfunction in the hybrid battery. One code indicates a regenerative braking issue but that's normal because the battery is malfunctioning. The P0A80 code is your primary failure. Unfortunately if you are unable to read the battery block voltages while the car is ready on your not going to be able to determine if this is the battery issue or not. Each battery block which consists of two cells has to be within .2 V of each other if it ever varies more than .2 V between blocks it will trigger this code. That means each individual cell can only be out by .1 to .015. Without being able to watch the voltage blocks on a data list it's virtually impossible to determine if you have a bad cell or a week cell. There was also a technical service bulletin for dirt or dust getting clogged in the intake air vent to the battery cooling system. Make sure the intake vent is not clogged with lint and dirt for the blower motor itself is clogged with debris.
There really is no minimum you can take it down to virtually nothing. If you wish there can be no variance in voltage blocks. The book says no more than .3 V I like to see no more than point. If you are checking each individual cell and not to the time you have to cut that in half. The HV battery monitors cellblock which consists of two individual cells. There are 28 individual cells total. The battery is designed to run between 20% and 80% charge capacity. I have rebuilt several of these and typically the lowest I ever see when you have one or two bars left on the indicator on the display it puts the battery voltage per cell at about 6 volts.
I do know that it does take some time for the cells to equalize when you are replacing a couple of cells with used cells. Make sure your intake air vent on the passenger side by the seat is clean and not clogged. About the only thing you can do is continue to drive the vehicle after the codes set then clear the codes run the vehicle so that you can get it charged to the maximum level then use just the battery and run the batteries all the way down as far as you can without getting the engine to come on so that you can work them from the 80% to the 20% level to try and get those two cells that you replaced to stabilize an equal out with the others. Or you could have another cellblock going bad. Without seeing the specific information codes and the battery voltage data list there's no way to know for sure without taking the battery back out and rechecking each block.
I understand that you have checked the batteries. However you could still have another bad cell or cell block. That is the only way this code will set or unless the battery is overheating because the cooling fan is not able to push enough air through the battery case.
have to measure the cell blocks individually or buy pairs they have to be within two-tenths of a volt. Cell block one is the farthest to the passenger side counting upward through Cell Block 14 on the driver side. When the code sets there should be some information codes along with the main code and the HV battery ECU will have a specific code number indicating which block has failed. If you don't have a code reader that interfaces with the HV battery ecu you need to have that done before you pull it apart it will tell you which voltage block and the data list as to what all of them are at.