How can I tell if my 12v battery is losing power, need replacement?

Are they talking about a dead traction battery or the 12V battery? No way a 12V battery is likely to last 7 years.

 

There isn't an idiot light for the 12 volt battery. For cars with conventional starters, you can hear if the battery is running low but we don't have starters in our vehicles. With the Prius, you can suspect a low 12 volt battery if: interior/exterior lights are considerably dim before powering into Ready mode and then brightening to normal brightness, the coolant thermos pump on second generation Prii runs considerably longer or with a lower tone after parking and powering off and so forth...

Even so, there's an easy way to test it without tearing into the hatch:
Weird stuff happening? MPGs dropping? Test The Battery | PriusChat

HTC Evo 3D

 

You can jump start a Prius battery, just be very careful to hook positive/positive and negative/ground. Reversing the connection can damage expensive components.

You can also try recharging a weakened battery. An intelligent, 4 amp or under charger, hooked up overnight or so might do it.

Assuming your battery's in the hatch area and there's a connection point under the hood: you can do the recharging at the under hood connection point. For jump start I'm not sure, haven't had the experience. Maybe best done at the battery posts? Some one else comment?

A battery that's assessed as good can go bad the next day, easy as pie: just leave an interior light on for a few hours.

 

welcome to priuschat! my '04 battery started to go bad in may of '12, so, they can last a long time if treated right and never run down. you will learn more here than you ever could from a dealer. so stick around and enjoy the show, it might save you from another tow. all the best!

 

Here is how to know if a Gen 2 (not a v, this thread has nothing to do with a v) has a low batttery.
Weird stuff happening? MPGs dropping? Test The Battery | PriusChat

 

If one recognizes symptoms and /or suspects a batteries end life is near, it is a simple task to take it out and have a load check done to it. A "competent" auto parts store or repair shop can do this.

Most car/light truck batteries have a reasonable lifespan of 4/5 years. I had one last 8 years, but that is the extreme exception.

 

I just took my 2010 Prius to get serviced at the dealer. Hooly shit what a rip off !! Besides all the crap they're selling me, the guy says my batter is low and I need to replace it. I believe It showed 12.7 volts ?

Then he shows it costs $188.95 with installation its $249.95 ... I was like, it costs $60 to install ?? GTFO !

First he said these are "special" batteries. Like I cant just get any Auto Parts battery and stick it in there. That's why its so expensive. And, if I were to take my battery out of another non-prius car, hook it up, I could blow up the car. Not literally, but just it woule screw everything up and Im not under warranty anymore.

Does anyone know where I can find the model or specifics of that battery ? I guarantee I can find it cheaper online, at another store, and I can install it myself. Even tho dont really think it needs to be changed.

 

My first recommendation Optima DS46B24R Optima battery direct fit replacement for Prius 2004 + , Prius V & Plug-in Prius with Instructions

Will also be safe (needs to be AGM with external venting, ideally with reversed JIS posts, all these are)
Exide AGM Car Battery (Group S46B24R)
Super Start® Platinum PRIUS - Battery | O'Reilly Auto Parts[/quote]

 

i would recommend not changing the battery, and not taking your car for 'dealer screw job' in the future.

 

lmseattle: The Prius can usually be jumped just like any other car using the jump terminals under the hood. Its possible that your battery failed with a shorted cell (which can happen on any lead acid battery, and can happen fairly suddenly) which will pretty much make it impossible to jump.

Actor: The Prius does use a special battery, its an AGM more like sealed UPS battery than a traditional car battery. Using an inappropriate replacement could cause all kinds of nasty problems, including hydrogen gas venting into the passenger compartment. Back in the day a common mod was change the batter terminals on the vehicle cables so that an appropriately sized optima yellow top (also appropriately sealed/vented) could be substituted. Still cost ~$150, but it was a much better battery and deep cycle so running it flat a few times wouldn't destroy it like the OEM. Luckily as Jimbo said several of the main stream deep cycle AGM manufacturers have now added a directly compatible model.

 

There is a warning/idiot light for the 12 volt battery.

When you make the car READY first thing it does is a bulb check and lights all the dash board lights turn on real fast. When the 12 volt battery hits below 11.7 upon start up load it will then illuminate a bright red caution sign in a triangle. That red caution lamp is part of that group to the left a little. You can see it unlit there on the dash if the sun is just right.

Its in the same area/group group of warning lights but never illuminates unless there is trouble. Under the 12 volt battery trouble scenario it only illuminates for a second and does not log a DTC. But very obvious.

First time my 6 year old battery threw that lamp out it came and I threw a Optima Yellow top in there.

That and if the 12 volt battery ever needed a jump it's pretty much done. If I bought the car used I would have replaced that 12 immediately. Because if the car sits there for any length of time and never started it will kill the 12 volt. The dealer will jump it and get you off the lot. Then your driving around with a time bomb. The time bomb is the 12 goes dead on you....you jump it...and cause about $4000 worth of electrical damage to the car. Thats a very common story here too.

Apparently the dealer is incapable of load testing that 12 volt battery. Heard the op's exact post hundreds of times here.

 

It's getting old. Your current year. ... minus 2014 ... Yes!! dump your aux 12v battery ... buy an optima yellow top , &move on!
.

 

why not tow it to another dealer? they will probably do it for $150 or so.

 

My area in Oregon, local Toyota dealers want from $250-$280 for a 12V installed.

easy enough to put in yourself if you follow the instructions on the forum, watch a youtube video or two...

 

I just replaced my 12v, and it was a learning experience.
You really can't just use any 12v battery. I bought the D51 off Amazon, which I thought was a replacement. I was able to make it work but it was a kluge and not nearly as safe as getting a drop in replacement.

It's an easy DIY just don't order your battery off Amazon late night, during a bout of insomnia

Also, get a modern charger that's AGM compatible (higher charge voltage).

 

I bought the Toyota battery from the dealer, just because I was afraid of some glitches with getting an aftermarket part.

It was $200 (prices ranged from $180-$200 from local Toyota dealers). But I saved the $80 install fee and learned a few things during my install "adventure."

There are most things that aftermarket are fine or better. Occassional things where it is better to go with the Toyota part....

 

Right. The D51(R) is a replacement for the CR-V and Roadster, what you want is a DS46B24R

 

wow sorry to hear that you went that route - too bad .... the oem really doesn't last that long ... We tried to support our other hybrid - a lexus - with OEM but it just did not work out for us ... the oem died prematurely .... but if you think hundreds of satisfied Optima people are wrong when it comes to purchasing optima - then - Google luck with that ...
.

 

Actually, judging from recent posts on PC from unhappy Optima purchasers who were sold relatively old batteries in discharged condition, I'd say there is more chance to be dissatisfied with Optima compared to buying GS Yuasa from your friendly Toyota dealer's parts dept - especially now that the latter comes with the TrueStart 84 month pro-rata warranty.