At what point do you replace the 12v battery?

i'm up to 49k. battery is STRONG.

 

Yeah, just like the stock market.

 

i'm in cd's.

 

Safe as houses!

 

I replaced the 12v battery in our (now traded-in) 09 Prius at about 80k miles. It would die (not "start" the car) if the interior lights were left on for more than a few minutes. Learn how to jump start your Prius (it is in the manual) and carry jumper cables.

One stupid thing we learned. My wife was on a trip and pulled in to a rest stop to take a nap at night. She always leaves the headlights switched on, and lets them "auto" off. This works fine as long as you open the door. In this case, she stopped the car, turned it off, and went to sleep. Because she never opened the drivers side door, the lights never turned off. They drained the 12v battery completely. Toyota should be smarter than that.

 

it's an unsolvable engineering problem. apollo 13 was easier.

 

Are these readings for a battery that hasn't been running for a bit?

I left my 2011 Prius off for a couple of hours, and I tested it with a digital multimeter I got readings of 12.06 and falling. And strangely, also, 11.96 and falling. Falling, meaning the reading drops.
This is the original battery, I'm the first/only owner and I bought the car in April 2011.

If I don't start he car for 2 days, it's a crap shoot as to whether or not the car will start without a jump start.

 

Original battery, I would just replace.

 

Thanks.
Is this list still a good standard for replacements? 12V battery List | PriusChat
Seems prices have changed significantly. The Optima listed at $147.05 on Amazon in the posting is now $289.99.

 

The $289 prices sounds like a case of limited supply, not the norm. I've kinda gone off Optima Yellow Top, and I have one. No problems 3 years in, but I've heard it has inordinately high Cold Cranking Amps, at the expense of amp hours. Internally that's achieved through more/thinner plates?

In the States Pep Boy seems to regularly have a conventionally shaped AGM by Bosch on sale, for around $145, and they'll even install for that price? As far as I know it's dimensionally identical to the the OEM Yuasa, with decent spec's.

 

Thanks!
I'm going to move forward and I'll get this one:
Bosch Premium Performance Battery Group, Size 51 - $142.49 including installation.

 

That's a great price.

 

Yeah. 25% off until April 1, 2018.

 

Thanks for your help.
I got the Bosch Premium Performance Battery Group, Size 51 - for $142.49 including installation Pep Boys. The car starts perfectly, now. I don't even think about the possibility of having to jump start it.

 

I worked for a guy that had a saying, "When in doubt, change it out".

Good luck with your car.

 

When switching out the 12V battery is it essentially unplug the old and plug in the new? Didn't know if there was more to the process than that.

 

I'd suggest something like this:

1. Disconnect negative cable clamp at battery post, that's the one that's not red. Maybe stuff it into a heavy rubber-lined glove, just to keep it isolated. A 10 mm box wrench is likely best for this. Take care to never make a circuit between the two posts, say a wrench handle or extension, a stray wire, or whatever. Just don't give it a path between the two.
2. Disconnect the positive (red) cable similarly.
3. Loosen and remove the battery hold-down bracket.
4. Lift out the old battery.
5. Clean the posts of the new battery, say with a scrap of fine sandpaper. Also clean the insides of the cable clamps. There are wire brushes purpose designed for this, though they tend to be on the big side, for regular size post clamps. Use what you have, again sandpaper will work. Just get everything to shiny metal. Be cautious with the post dust, it's lead.
6. Put in the new battery, install the hold-down bracket, and install the clamps in reverse order: red first, then black.

Some caveats:

a. It would be good to pre-charge the new battery, with a smart charger, 3~4 amp range. Let it run to completion, might take 8 hours or so. It's not mandatory, if you've got a fairly fresh battery and are going to be driving a lot it'll be fine. But if you have the charger and the time, it's good practice.
b. You will lose some of the car's memories if you don't employ some sort of memory saver. You can either research that, or just resign yourself to having to reset a few things. The trip meters will reset, radio presets will be gone, and if the car has auto-up windows that may need to be "relearned". You may be ok on that. It's not the end of the world, and there are procedures to remedy the window issue, if it happens.
c. Check conditions under the battery while you have the old one out: there may be water collecting, for example.

 

(I have a 120,000 mile/10 year service coming up August 16th)
I have been noticing my head lights get brighter about a second after I start the car for the past two weeks. Today I altered my Scan Gauge II to display volts instead of intake Air Temperature F. When I turned it off, I had 12.1 volts. (14.7 volts when running) I am going to monitor it cold each morning, but it is clear the battery is on my replace list when I go to the dealer in August.