How long do I have with this dying 12V battery?

Sorry I misunderstood or misread your original post.
However, over the internet, how can anyone really predict how much life you may have left in a battery?
I've owned vehicles where I'm standing right over the open hood looking at the battery, and really have no idea if the next crank is it's last. Even with voltage readings, and meters -it's not too predictable.
Over the internet, it's impossible.

 

I researched these 3 Trunk located 12 volt batteries for my 2012 Prius Plugin, and found them all to be very good batteries, but after reading all the information. I thought the ("Optima Batteries 8171-767 (DS46B24R) Yellow Top Battery") was the best, and purchased it at $141 at 4WD & Bosch S6535B S6 Flat Plate AGM Battery Group: S46B24R at $145 was available at CARD & Exide Edge FP-AGM-51R Battery was $144 was available at CARID. I don't think I would have went wrong with anyone of these, but I do think these are the best three of a Prius trunk located battery, because you have limited space to place the battery in, and really no room for error, and these three batteries are built just for the Prius trunk located battery. I am sure with more searching could have found more to choose from. Now for my question to my other 2012 thru 2015 Prius Plugin owners. What news have you heard about the recall for the Hybrid battery fuse replacement?

 

i haven't heard anything. if i wait long enough, i can do the airbag and fuse at the same time. anymore toyota recalls, and i may have to look at another brand.

 

Probably best to ask Gen 3 specific questions in the Gen 3 specific forums.

 

Maybe not.

If those voltage readings were taken with the car in "ready" mode, then your charging system is suspect.
When the vehicle is ON and no major drain is present, the voltage should read at least 13.2; absolute minimum.

If the new battery wasn't manually charged before installing, you should do that now.
A fresh AGM battery that is fully charged should read at least 12.8 with no load.

 

Check voltage first thing in morning with a digital multimeter, with the car off. If it's still reading 12.4 that's kinda fishy.

A good ploy is to get the installers to check it with an electronic load tester, ensure you're not getting a stale battery. Hopefully it's just a case of the car's peripherals pulling the voltage down.

Bottom line: it's really hard to make sense of a voltage reading taken by the car's display, too many variables.

 

argh! you ruined the thread. we were taking side bets on the over/under.

 

Yes but after it's been off and undisturbed for an hour or more, and without the FOB close by, the current drain should be negligible.

IF a battery cannot support that slight current draw without a drop in voltage, there is something wrong.

There IS a significant difference checking it with an external meter.

 

i pop the hood the night before, and measure it at the jump point in the morning. if you can't do that, reach in through the drivers door so you don't activate the brake pump.

 

the battery is likely good, but sometimes they don't come fully charged. nothing wrong with that, but it should be done since the prius makes a lousy charger. a fully charged new battery should be around 13v with everything off.

 

Well in the end you bought it locally and have the warranty.

Posted via the PriusChat mobile app.

 

Thank you for not making it more complicated than it is. The guys are probably right, that it is not at a fully charged state straight from the shelf, but as you are saying, it is good enough. Under normal conditions and as long as your charging system is working, especially on a low amperage draw prius, you will never be able to tell the difference between 100% SOC and 50% SOC on the 12v battery. In either case, it's going to perform its intended job. This is a case of install it, drive it and forget about it. 99% chance you wont be touching that battery again for a handful of years.

 

Should be getting a letter from Toyota starting January 2018