Replacing 12v battery and headlights next week. Need advice.

welcome to priuschat! great move on the optima, if it's under 12.7 volts, i would charge it first. sorry, i know zero about headlamps. all the best!

 

Good luck with the Optima, I had to return mine 2x because they were subpar. I finally just went to the dealer and paid a premium for a known good battery (YUASA).
To answer your question, I would bring a multi-meter to the posts of the new battery to determine if it will need a charge before installing it into your Prius. It should be resting around 12.8v.

As far as the headlights go, if you have the HID's, it is so easy to replace the bulb AND they are cheaper than anywhere else on amazon - I paid $45 or something a while back. That was 2 years ago, and the bulb still works great. See youtube for some really nicely detailed instructional bulb replacement videos.

I believe this is the exact bulb you will want:

Amazon.com: Philips D4R Xenon HID Headlight Bulb, Pack of 1: Automotive

 

with that kind of driving, i would put a charger on it if it's under 13.0 volts. the car will never have a chance to charge it.

 

it would be a good idea. your best bet would be a permanent pigtail, so you don't have to dig into the battery every time. or you can go under the hood, if that's easier.

 

I'm guessing part of that $1200 is a leveler for the HIDs. That is problematic with HIDs. Search here for other threads about the leveler. I'd start with the bulbs like you are doing, but it might not be all that ultimately needs to be done to fix your lights.

 

I just attached the pigtail to the battery terminals routing the cable up through the ring on the right side. The other cable runs the length of the car down the right side with the transformer sitting on the floor of the passenger front seat. I run an extension cord through the open front window when it's charging time.

 

there is at least one thread here, but i can't point to it, sorry. it may have been posted by member 'andyprius1'