12v almost dead. What replacement fits?

The auto parts stores sell over-priced batteries for Prius... Main reason being Prius 12 volts are not normal 12 volt car batteries in that they don't power a starter motor because the Hybrid battery pack does that, so you don't need much from a 12 volt battery, which means lots of rip-off sellers like Optima Yellow Top and others are scamming people simply because Prius is different.

Batteries Plus most common AGM 12 volt battery that they sell at $130 for wheelchairs and back up computer power supplies are the best because they sell so many of them that there's never an issue of them sitting on a shelf for too long. They also have way more amp-hours then the $230 ones the auto parts store recommend. Only issue is that terminal mounting hardward is slightly different so you'll need some longer bolts and bushings from your local hardware store.

 

try auto parts, internet, dealer. not sure what you can get in hawaii.

 

Speaking of the 12V battery, how am I going to know when it's on its last legs? With a conventional car, you can tell because it struggles and takes longer to crank. It seems that with the Prius it's fine...until it isn't? Will it give me a clue when it's time or will I just not be able to start the car? I have a 2012 with 110k miles. Not sure if this is the original battery (I bought the car with 34k miles on it), but I've never noticed any issue with it starting, even through last winter's brutal cold.

 

Use the MFD to get a sense of battery voltatage while it's under load. If it gets lower than 12.6 volts it's probably time. Also to extend it's lifespan get a cheap $10 trickle charger... They charge the battery up to ~13.8v and if it can't hold that charge after sitting unused for a couple days, that's another sign it's time.

 

Well, it never sits unused. Only time was when we were on vacation for a few days. Normally it's drive 80+ miles per day.

 

Which is why Toyota recommends changing the aux-battery in their hybrids every three years. It's part of the normal maintenance schedule. You could probably get away with four pretty safely, but if you want a well maintained car that won't leave you stranded, I change the batteries in all of my hybrids every three years, along with the key FOB batteries.

Problem with batteries, is that you can test a battery with a battery tester, and it'll prove OK. Three days later, it isn't.

 

Saw the 51-440BAGM Bosch Battery mentioned in a previous thread. People here still like that one or are there other recommendations?

 

Do you have a number or more details than AGM 12v? I think that covers a lot of ground.

 

Lol... Most 10 year old Prius are so well designed they're driving on original battery simply because there's never a cold cranking amps load. And yes that may not be what's recommended, but it's the truth, I've seen it again and again and again... That's why it's the first repair issue to be addressed before all the others!

 

Here's the most recent one I bought for my friend, they change from time to time, but they're pretty much same size and amp hour, at least in the US: Duracell Ultra 12V 55AH AGM SLA Battery with M6 Terminals

SLAA12-55C/FR