When to Replace 12V Battery

How does one know when the regular (non-traction) battery needs to be replaced. 2014 prius. What are the warning signs? When I press the start button all lights come as normal EXCEPT the green ready light. All other lights keep blinking showing they are working. After a few attempts then the Ready light comes up and car is operational. Does this simulate the grinding of a non-start button car indicating a worn out battery? What brand battery is recommended for replacement? Is walmart's everstart could enough? thx for any info.

 

You want to replace it now....at 10-years you've gotten about 3-4 years of extra life! Many reports of scary electrical issues show up when it's close to dying.
I just replaced my wife's 12-volt in her 2017....it was testing at 70% with my tester. (You can get the same check free at any car parts store.)
$208 at my dealer for a Toyota TrueStart with cca 470 with an 84-month warranty.

 

Is it the original 12v battery? If not, how old is it and what brand?
Toyota makes the best battery for their car. And no "making it fit/work".
I do recommend charging it for about 8 hours at 5 amps or less. They don't charge
them at the dealerships or parts stores.

 

same battery in car since purchase (18 months ago) happy to replace it. this car has been the best ever owned. totally trouble free, great gas mileage. this with 250k miles 31k of which i put on it. will go to dealership to tommorrow and replace it with new toyota one. appreciate your and coloradoboo's help.