12v battery

You can get that battery tested at most auto part stores. Don't have to guess at it.

 

1. How often does the car get used, and typical trip length?

2. Ever left a door ajar, lights on or similar, run it down?

3. Do you ever leave the car in accessory mode (one push of start button without foot on brake), or “on” mode (two pushes of start button without foot on brake), for protracted periods. Say sitting listening to radio, or running AC while parked.

4. Recently had the car in a shop, say for detailing, something installed, etcetera?

5. Do you have some accessory that draws power while the car is off, say a dash cam for example? Anything else constantly plugged in?

Consider doing a check for phantom loads; all cars have “some”, but with Prius it should be no more than about 20 milliamperes.

 

We’d be bored here without speculating on anything

 

I just had a battery on a Lexus GX460 fail on me this week. One day it just wouldn't start, not sure if I left an interior light on. I charged it and it seemed to have worked afterwards. It's only 2.5 years old, original battery from Lexus (Panasonic). However after I charged it I drove it over to an auto shop (Autozone) and they tested that battery to be bad. They told me although it's charged and working, the battery will not have the cranking amps necessary to start the car when it's cold.

With this information, I brought the car to Lexus and they also tested it bad and gave me a new battery (under warranty).

 

For DIY, the tester they're using is likely a pro version of something like Solar BA9, relatively cheap pro-sumer level tester. There's other similar testers; this is just the brand I got.

Review of earlier version, BA5 (the one I've got):

 

I can speculate that!

 

You probably realize that that statement exceeds the intelligence level of most PC members, right?

 

I noticed the GLARING ABSENCE OF “Left the hatch open multiple times”!!!!! LOL

 

I'm still dying how pomp and circumstance over here is wearing a lab coat

 

To the car, that's equivalent to "door ajar," which he did list. (Should've said "door or hatch ajar or only half-latched.")

It takes roughly 2 days to severely discharge the battery that way even if no interior or door lights are on. Shorter periods will shorten its life, roughly in proportion to the number of ampere-hours lost.