Auxiliary battery happy voltage

did you measure it after the surface charge wore off?

it's hard to put a number on it. low 12's is getting iffy.

there are a million reasons why the engine might run more. best thing to do is track your mpg's at every fill up.

 

What have the temperatures been?

 

southwest heat is hard on all batteries.

 

That sounds fine, but: 5 years old, I'd replace it anyway, leave on a high note.

 

I always try to squeeze all I can out of a 12V battery and my wife says just change it. I started listening to her, that way I can never be wrong again. DAH

 

I hear that emergency vehicles, ambulances and the like, change batteries every two years. Overkill, acknowledged, but just a decision they've made.

 

The contract for my whole house generator wants you to change the battery every four years, mine only lasted three.

 

So did you dutifully wait one more year?

 

Measure it at the jump points. A lot of work to measure it at the battery and that really doesn’t matter what
The voltage is there what matter is what’s getting to the main fuse box then the inverter. Got a few fuses and a long heavy duty cable before it gets there. That’s the true working voltage. At the jump points.
After 11 years I have never measured the battery voltage at the battery.

Measure there with the car off then measure again with the car off and turn on the headlights in high beam to check it’s capability to deliver under load. Measure with high beams on car NOT in ready.

And I’d be way more Concerned about the traction battery’s health than the 12 volt.
12.7 is pretty good. Unless it dips down to 10.7 under headlight load,

 

For future readers.

Other day I measured my 2 year old optima yellow top.

12.63 resting volt at the front battery jump points.
12.1 with car off and hi beams on.

So if you see more than .5 voltage drop at jumps with headlights on hi beam and NOT READY start giving your 12 volt battery the stink eye.

 

Acceptable voltage drop changed a lot depending on conditions. If your battery is cold and especially if it’s not charged full (happens easily if you drive short trips in cold temperature) bigger voltage drop is still fine.

 

If you've got deepish pockets and want in-depth assessment of the 12 volt, pick up a Solar BA5.

 

I've had great luck using cheap solar panel trickle chargers to extend the life of marginal batteries, and the Prius seemed a perfect candidate for this solution – expensive batteries, lots of current-draining electronics, slow recharge rate. I learned the hard way that leaving a door open (even with no lights), or leaving the key fob in the car can quickly drain an older battery. With a replacement battery costing at least $150, these chargers can easily pay for themselves:

This being my first post, Priuschat won't let me include links to Amazon. But you can do a search for these products:

Low output, but very easy to install:
ALLPOWERS 18V 5W Portable Solar Car Battery Charger

Higher output, but requires regulator (and maybe an in-line fuse, to be safe):
ECO-WORTHY 10W Solar Panel
Y-SOLAR Solar Panel Controller PWM 12V/24V
EPAuto ATC / ATO 10 Gauge 30 AMP In-Line Fuse Holder
I hooked one of these directly to the battery, and leave it in the “trunk,” catching sunlight through the windows. This regulator also has usb outlets – handy for charging your phone on a camping trip…

 

I hope you haven't been holding your breath for a reply but I changed that battery last year, about 15 days out of warranty.
Sam's Club said it had a dead cell. My electrical service took a hit by lightening and I think that cooked my battery, I lost a 20 Amp circuit breaker at the same time for the charging circuit for my generator. It didn't seem to hurt the generator, I heard it doing it's weakly test run today about 11 months later.