Replace one cell or entire battery

Possible, yes. Desirable, not without proper testing:

1. replacement module needs to have the same Ahr capacity (measured) as the others
2. replacement module needs identical charge state as the other modules

In practice, this requires in effect rebuilding the whole traction battery. Then there is the problem of making sure the buss bars are OK. Often a failed module is associated with electrolyte leaking and this tends to corrode the buss bars and sense wires.

Over the years, we've seen a high failure rate, ~2/3, after single module replacements in the 2001-03 Prius.

You might consider adding your location to the profile. This makes it a lot easier to identify independent Prius shops that can offer you another option.

Bob Wilson

 

The common path of least resistance is to hand your battery over to a rebuilder in exchange for a refurbished one. They'll repeat the process with yours, balancing, replacing cells as needed, and so on. Re-Involt is one company in this business; I think they're refurb Prius batteries will set you back just under $2000, and you'll need to spend about another $300 with one of their authorized installers.

 

There have been a couple of threads recently with people replacing cells. It is a learning process, and requires a good bit of your time. Although it is not difficult work, you will have to determine if your time is valuable enough to make going through the rebuilders mentioned above a good option..

 

Prius Battery fails, just after warranty expires! Interestingly enough my flailing diminished power 2006 Prius limped into a Toyota dealership this morning, and received a diagnosis of "battery not performing as expected" and needs replacement to the tune of $3598.00!!!!! This is a Prius with now 160k mi, and apparently Toyota offers a 10yr / 150k mi. warranty...but it doesn't cover this one! Anyone else with similar experience? What are the alternatives to getting the battery replaced without the high price??

 

^^^
Failed traction (HV) battery, what to do? - Prius Wiki

Notice the statement from the Toyota brochures I quoted at Prius Battery Issues | PriusChat.