P0A80 replace battery pack vs P0A80 Battery ECU error

Can you post scans of the Dr.Prius reports?

 

If you look in the repair manual (which is the right place to look ), you only find the correct one, (1).

Gen 3 no longer has a thing called a battery ECU. In earlier generations there was one, and it was an ECU in its own right, separate from the HV ECU up near the dash.

In gen 3 there's still a little box with wires back there, but it's been demoted to "battery smart unit" or "battery pack sensor module" and it's pretty much just a remote-sensor annex of the power management control ECU in the dash.

There is a P0AFC code for a problem with the sensor module, and a P0A1D code for a problem with the power management control ECU. But P0A80 is a judgment on the condition/performance of the pack. All of these codes are in the P0 range where codes are standardized industry-wide by SAE, so Toyota doesn't get to play with their meanings.

 

Your high voltage battery has problems. If you simply swapped modules around, it won't solve the problem. It may fool the high voltage battery computer for a short time, but after a while it will fail.
On this screenshot (Screenshot_20250428-205231_Dr Prius.jpg) in the fifth pair of modules there is a problem with one module. The voltage difference between adjacent modules is more than 1V. This happens when one of the six cells in the module is damaged and then the module has a voltage of not 7.2V, but 6V. The battery ECU measures the difference between adjacent pairs of modules and when this difference reaches more than 0.3V, it generates a battery error code.
On this screenshot the problem is in the 12th pair of modules.(Screenshot_20250428-004929_Dr Prius, Screenshot_20250428-005438_Dr Prius, Screenshot_20250428-205205_Dr Prius)
Tech Tips

DTC P0A80-123 is stored when a malfunction is detected in the HV battery or battery voltage sensor. If the HV supply battery is malfunctioning, the malfunction may not be reproduced when the condition of the HV supply battery changes due to difference in driving load (amperage), battery SOC and battery temperature. Therefore, use the freeze frame data when performing a repair.

• When the HV battery is malfunctioning:
  
  
  • Voltage of one or a few of the battery blocks has dropped. (voltage difference from that of the next block is 1 V or more)
    
  • Voltage of all battery blocks is output randomly with no certain pattern.
    

• When the battery voltage sensor is malfunctioning:
  
  
  • Differences in battery block voltages have a certain pattern.
    

• In order to ensure HV battery performance, appropriate cooling performance must be maintained. Perform the following as necessary:
  
  
  • Make sure the air intake port is not blocked.
    
  • Make sure there are no gaps between the connecting parts of the ducts.
    

INSPECTION PROCEDURE



Battery repair consists of diagnosing all modules for their residual capacity, internal resistance and self-discharge (voltage reduction). Then, rejecting faulty modules and replacing them with serviceable ones.