02-10-2021, 11:34 PM
Gareth wrote:
If the battery itself is bad, a charger/maintainer isn't going to do anything, because even if fully "charged", the battery may not have enough cranking amps left to actually start the car. I.e. it might be at 12V but only at 10% of its original capacity.
In a Prius, the 12V battery is more like a PRAM battery, it doesn't do any "cranking", it just keeps the electronics alive to startup the systems to get the traction battery system engaged. The main thing that normally drains the 12V battery when the car is "off", is the keyless access system. I think it also keeps another rechargeable battery charged that is used for the brake system.
From my experience with a 2007 Prius, the need for jump starting became more frequent when the battery was about 6 years old, and stopped occurring when I replaced the battery.