P0A80-Replace Hybrid Battery

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WHAT IS P0A80?

Short answer: The diagnostic code P0A80 means that the hybrid battery is failing and needs to be replaced. Other codes may accompany P0A80 such as p3011, p3012, p3013 etc. Those codes refer to the individual block of modules (commonly called cells) that are causing the failure. If your hybrid has P0A80 and you need a replacement or some guidance please reach out to us.

Long Nerdy Answer: Toyota, Lexus and Nissan use a similar battery technology, but I will use the Toyota Prius for this example. The Prius traction battery utilizes 28 modules with six cells to each module. The modules are paired off into “blocks” of two.

The P0A80 will be present when the BMS (battery monitoring system) has detected a voltage difference of 20% or more between the battery blocks. Typically when the P0A80 code is present, one of the 28 modules has failed and more will fail soon if the battery isn’t replaced or properly refurbished. Some companies will replace just the failed module and send you on your way, only to experience another failure within a month or so. Just replacing one bad module is a band-aid repair on what will be a continuing headache, costing more time and money than just replacing the entire battery. In this situation, all the cells should be replaced with others that have been properly cycled, tested and have similar metrics.

Why did my battery fail?

Aging NiMH battery cells are subject to develop what is called a “memory effect.” The memory effect can happen if a battery is repeatedly charged before all of its stored energy is depleted. Hybrid vehicles are prone to shallow cycling because they typically stay within a 40-80% state of charge. This shallow cycling will eventually cause the formation of dendrites. Dendrites are tiny crystalline-like structures that grow on the separator plates inside the cells and eventually block the flow of electrons. In addition to the memory effect, an aging battery may also develop rising internal resistance which causes the battery to overheat and abnormal voltage drops to occur under load.

*Notice that the blue line indicates a module that has high internal resistance, but would have passed tests based on other metrics.
*Cell #23 had normal voltage and capacity, but a high internal resistance was evident under load.

In very rare circumstances the P0A80 code can be caused by corrosion on the voltage sensor harness/bus bars or the hybrid battery ECU. We have only seen this occur a few times in the thousands of batteries that we’ve come across. Typically when corrosion is causing a failure, other codes (P0A7F, P0A1F, P0AFA) will be the main DTC.  Fun fact: our refurbished batteries come with nickel plated bus bars to prevent corrosion!

Engine and braking issues:

Your hybrid battery utilizes a combination of engine power and the regenerative braking system to help it charge. If one of the systems fails, the battery will not charge properly. More information can be found here and here.

How do I know if my hybrid battery is failing?

Check out our FAQ!

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