2010 Prius, 12v battery or key fob battery? "Key fob not detected"

sounds like either/both, but might as well start with a fresh fob battery. 10year old 12v? i would replace it if it were me. idk if that is the right size, but it is a great price.

 

Best to replace the 12v battery, it will soon start giving you hybrid errors.
Make sure you charge it for 4-5 hours at 5 amps or less to give it a full charge before
installing....
Key fob batteries are inexpensive, won't hurt to change it...

 

You need to replace the key fob battery. 2.8 volts for that battery is very low. A new CR1632 battery should measure about 3.3 volts.

I just replaced my wife's key fob battery today because she got the same "Key fob not detected" message. She said she had to hold her purse close to the dashboard for the car to detect the fob. I measured the old fob battery at 3.00v, and the new battery I installed was 3.3v.

The 12v battery you show in your post is the correct one. That is a very good price for the battery.

 

One of my pet peeves is "keep replacing parts until it works."

 

I agree. If you already carry a jumper pack in your car, I would wait to replace the 12v battery. If you do not have a jumper pack, I would not hesitate to replace the 12v battery, especially at the price you show in your first post.

 

Don't think, FEEEEELLLLLL!!!!
Cause you'd be thinking wrong. In a Prius, that's a dead battery. 12.6, maybe 12.5v is the lowest
for the Prius computers to function properly. And after 10 years, It's lived a good life and served you well.

Avoid issues, replace it will a new battery, and charge it.....

 

That's not true. Can you please provide the link to the Toyota documentation that states that the Prius computers need 12.5v or higher to function properly. I have read multiple posts made by @ChapmanF that the computers in a Prius will function properly with a 12v battery as low as 11.5v.

My 12v battery has been in the range of 12.4v to 12.2v over the past year or so. It has worked flawlessly. Car starts every time. No trouble codes or warning lights on the dashboard.

 

My car is rendered inoperable when the 12V battery falls to around 11.5 volts.

 

The Toyota repair manuals are full of troubleshooting procedures with an early step like this:



... which is not, by the way, anything like a statement that anything < 11 V means stuff will go wrong. It means that below 11 V you might want to charge or replace it to rule it out as a problem before proceeding to other troubleshooting steps, whereas between 11 and 14 V you can just go ahead with the other steps.

I've never seen a Prius start misbehaving until substantially below 11 V. There are some ECUs in the car that will start logging "hey, did you notice the voltage is low?" codes around 9.5 V. (Those ECUs, of course, are at that point still working fine, and executing their programming to tell you about the voltage reading they noticed.)

A Prius that "is rendered inoperable" "around 11.5 volts" has something mighty unusual going on.

 

You'd think...
But the dealer disagrees. They blamed me for draining the battery by using a cellphone or some stupid such stuff.
I have left my car parked for as little as 2 hours, to return to it, unable to start, requiring a boost. I think it's due to the wireless updates, which are unpredictable.

 

you need to have the 12v load tested if you don't want to replace it. you can get a free test at many auto parts stores