My 2005 Prius has been acting weirdly recently. I pressed the FOB on 2 occasions and nada. Replaced the FOB battery. Same problem again. Once the alarm went off. The clock resets itself. And the fuel guage blinking meter resets itself the last few times I started the car. Also, the mileage tally in the screen has been resetting itself to "0" now too. The Prius guy at the dealership says maybe it's the aux battery since the Prius computer starts acting crazy when the battery starts going. Any thoughts would be appreciated. Also, if I replace the battery myself, do I have to disconnect anything to do with the hybrid system, or is it a regular terminal connect like in a regular car?
Yes, your car needs a new 12V battery. You can DIY replace it, there are many posts about how to do so. There aren't any safety issues specific to the hybrid drivetrain. The safety issues are the same as with any 12V battery replacement: observe the correct battery terminal polarity. The negative terminal is the first to disconnect and the last to connect. Keep away from battery acid (if your battery happens not to be AGM.) A danger of explosion exists due to the battery's production of hydrogen gas. Good luck.
dpframing, If you don't mind doing just a LITTLE more work, I would recommend this battery and installation kit. Took me about an hour to install, it was cheaper than an OEM Toyota battery and reviews on this site seem to indicate far superior in performance. Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004 - 10
