I have seen the post for replacement 12 volt battery I can't post link, because this is my first post, but it would show up on a battery AND Optima search. Has anyone found a better price than elearnaid.com? Currently $165 for D51 Yellow top Optima with free shipping and installation kit. Also can't post this link, but viewable on link that would show up on above search. Also, can anyone recommend an ignition coil and good price source. I have seen them online anywhere from a WSO coil for $43.95 to YEC coil for $107.95. I have replaced the spark plugs and noticed some light burn marks on the outside of the coil from cylinder 2. Some slight rough running on the highway. Mileage slightly down. May be combination of low battery (showing 10.1 volts on display test) and burned coil. 2005 Prius Original Owner 170,000 miles.