Repair/replacement of individual HV battery modules

Many hybrid vehicles, especially Toyota Prius and similar models, use a high voltage NiMH (nickel-metal hydride) battery pack. This battery consists of multiple individual modules connected together. Over time certain modules may lose capacity or begin to operate unevenly, which can trigger hybrid system warnings, reduce vehicle performance, or cause rapid battery discharge. With proper diagnostics it is often possible to identify the specific failed modules and replace only those modules instead of replacing the entire battery pack. In some cases repairs can be performed directly in the vehicle without removing the entire battery assembly, or with only partial disassembly of the battery pack. After module replacement the battery is balanced and the cooling system is inspected to ensure proper operation. Repair cost depends on the battery condition and the number of modules that require replacement.