Gen 2 2004 Prius 200k miles. Bad battery cells. How hard is module replacement?

Sure it’s a great idea if you doing the job for the first time but if you know what you doing it’s not necessary, I feel very confident with my battery after working on it out the car like maybe 5 times, first time to clean the bus bars, second time to torque because first time I didn’t have the torque wrench third time to install the prolong harness and inspection of my hybrid battery four time to check the reason of morning recalibration aka weak modules but nothing changed this time and a fifth time to replace the previous selected modules, as you can tell by now, I enjoy working and learning my car and I can take my battery out the car in just minutes, so with my previous experience I pretty much know very well my hybrid battery, I will make sure at the dealer I am not giving out anything that am no receiving plain simple with my experience.

 

Your observation is missing some of the science of nickel-based batteries, which loose capacity over time... Remember camera batteries before Lithium? Many NiMH AA batteries had chargers with a function called "conditioning" or "deep cycling." This is because after lots of cycles poorly conducting crystallization build up inside the battery diminishing capacity and by deeply discharging and then low amp pulse recharging you can restore a prius pack from %50 capacity back to 96% capacity, which is the primary function of Prolong system.

Toyota on the other hand was not interested in including equipment that could do this in each car, but rather choose to make money selling new battery packs and designing the firmware to operate normally with a pack that's lost as much as 50% capacity as indicated by your screen in the car showing battery charge level fluctuating rapidly... Learn more here: BU-807: How to Restore Nickel-based Batteries – Battery University

 

You absolutely right about my observation is missing the science it’s only from my own experience and I open to learn from others here that is the reason am here on Prius chat.

 

There's lots more to learn about hybrid cars compared to regular cars. More you learn, more money friends and family save when it's time for repairs.