Thanks for the reply. And to follow note with the other posters here my battery died at almost exactly 52 months
Same here, 2011 Prius, purchased April 2012. Battery died yesterday at 65k miles. Replacing with Optima yellow top today.
my 3 pri 12v lasted 8 years, 8 years and currently 4 1/2 years, still reading 12.7 volts cold. but if you've ever run it down, or 'don't wanna know nothing', 4 year replacement is probably a good idea. but i hate to see perfectly good anything's go to waste.
Optima yellow top went in today without a hitch. Measured 12.6v before installing, I didn't try charging it when I got it home. While I was in there replacing the battery, I checked the air pressure in the spare. Max psi is 60, it was at 40 psi, so I inflated it to 60 psi.
For those of you that are replacing your battery with an AGM battery (like a yellow top) a glass matt battery probably shouldn't be topped off with a regular trickle charger. you should get a charger that is made for agm batteries
One key to the battery longevity is to not create a battery drain. It seems these batteries can take one discharge and then fail shortly after without warning. That is where the recommendation comes to change every 4 years if you do not want to be caught by surprise in a bad situation. (Or worse your wife or kids!). My battery was about 4-5 years old when my wife left an overhead map light on overnight. I re-charged the battery and all seemed fine. About a month later we came out after church and the car would not start. When I tested I read about 11.1V. I was at the dealership Monday morning purchasing a replacement battery.
Measured the voltage today at the jump point under the hood and got 12.7v Read on the web that a fully charged yellow top should be around 13.1 or 13.2v, so I put it on a charger set for 2A for a couple of hours. Measured later at 13.1v, much better.
I never ever see 13.1.or 13.2 with my yellow top/ if I put a battery tender on, yes; otherwise no/ what I see usually is like 12.8v /
will be interesting to follow it over time. maybe the prius can't maintain it at that level like a charger.
it's not the prius, it's the battery. the lowest voltage I get while driving is approximately 13.5v, so there's no problem from the charging side/ but no matter what, after half a day the battery is down to 12.8v & stays there/
12.8 - 12.9V is what I typically read on my new Toyota battery also. I can charge it above 13V overnight and in a day or two it will be back to 12.8.
Remember there's a small constant drain on the battery (~.02A), plus larger intermittent ones if you open a door (especially the driver's), or use an interior light, etc. Therefore, battery voltage will drop more in a few days in the Prius than it would drop in an isolated battery.