Dome light, key fob, clock, no radio, VSC

Suddenly on my 08 Prius, the dome light, key fob, clock doesn't work, radio will not come on, also VSC shows up on the dash, fuel gage is slow to respond.

I checked the dome light fuse and it's OK. I went through the battery check and it shows 11.4 volts.

History: Left the rear door slightly opened for a few days, about a month ago, battery was dead, charged it and everything was fine. Changed the passenger side rear light a few weeks ago, all seemed fine.
A few weeks later, I drove it to get a sticker and noticed fob didn't work along with all the other problems.

This is not our daily driver. I only use it to go a few miles around town on occasion. I assume I could still drive it without any problem and it is just an inconvenience.
Any ideas?
Thanks!

 

Trouble code reads C1231.

Bought the battery in Dec. of 2013, it's a 84 month battery.

 

Has about 102,000 miles.

Can these batteries take a conventional charger, or does Toyota have to do it?

 

The car starts and runs great. Just the problems I stated, everything else seems fine.

 

Problem is gone!
Here's what I did:
I drove the car around town for about 1/2 hour, making sure I used the brakes often. Then I parked it and left it for 2 days.
Today, I took out the dome light fuse and checked the voltage. Didn't appear to show any voltage, so I checked the voltage going to the fuse box and it was 11.9 volts. Checked the dome fuse holder again and it also read 11.9 volts. Checked the fuse and it was good. Wiped off the contacts just in case they were dirty. and put everything back together.
In the car, I did the diag. check by hitting the power button twice, flicking the lights 3 times while holding the info button, and the reading for the battery was 11.9. Started the car and it went up to 14 volts. At that point, I noticed the dome light was on! Restarted the car, and everything was working, and the VSC light was off.
So, now it's all good. Not sure if driving for 1/2 hour, working the brakes, or something with the fuse or fuse box was the problem, but I'm glad it's all good now.
Thanks for all your input!

 

I don't think Toyota will honor the 84 month battery warranty if the battery is working. So I guess I'll have to wait.
At least I know what it is now. Just glad it's not something more serious.

 

After 2 days of not driving the car, problems are back.
Not having much luck with local Toyota dealer. Over the phone, they said just bring it in and we will check the battery, no charge. When I got there, they didn't know they didn't know how to check it, so they wanted to pull it into the garage. They wrote up a service work order for a battery check, an oil change and multi point check...
Wait a minute, I just wanted to have them check my battery! Still, that would take an hour and a half. OK.. Got back in my car and left.
I'm probably going to just live with it till it's completely dead. Then get a new battery at a service center.. Not Toyota.
Thanks for all your help.

 

When I drive the car for a half hour or so, it goes away, so I think it's the 12V battery. I plan on getting a new one in the spring. I don't drive the car much in the Winter. Let me know how you resolve it. Is your battery 5 years or older? If so, it is probably that.