What happens when your Hybrid battery fails

yes, but you might have to disconnect and reconnect the 12v to start it.

it depends on how bad it is. generally, it is a slow degradation until it will no longer start the car.

best practice is to repair or place at the earliest possible time, after symptoms begin, like trouble codes, or oscillating battery gauge between high and low.

 

Resetting the trouble code works, and is less trouble than disconnecting the battery and then having to reset everything the car forgets when you do that.

It works, that is, until it stops working, and then it doesn't. Sometimes that moment is announced with a bang, bad smells, and a walk home.

 

Monitor "Voltage diff"on Dr. Prius app... As that number goes up, the lifespan of battery pack goes down. Also deep cycling the battery several times every 18 months will restore capacity and keep the voltage difference number low.

And because you clearly value your car enough to upgrade to Gen4 engine, you need to start saving up to upgrade to a lithium aftermarket pack: https://projectlithium.com/?ref=9qLPw

This pack will make you feel the same contentment as when you first put your Gen4 engine in... You'll have increased EV range, pack will recharge more efficiently, climbing mountains down to two bars will still have solid battery power unlike OEM and near 1/2 the weight of your old pack. Also HVAC system runs stronger too!

 

prolong-battery-charger

 

Read the FAQ on the website Bisco linked so you understand the basics... Also read this: BU-807: How to Restore Nickel-based Batteries - Battery University

And if you want to build your own equipment rather than pay alot to Maxx Volts or Hybrid Automotive, follow our discussion here: Build Hybrid Battery Maintenance Gear For Under $100 | PriusChat

 

It looks eye-catching but what's been done to modify the charging circuit of Prius to work with lithium cells?
Prius' charging system is optimized for NiMH type cells. Lithium cells have different charge algorithm.