Optima Batteries 8171-767-FFP YellowTop Battery

So, these batteries are made for a Prius. What I find interesting is that while the charge voltage is 14.1V in the car, which is fine, that battery seems to carry a steady state voltage (after sitting for 8-10 hours) of about 12V. The Steady State voltage should be 13-13.5V, not right at 12 volts. I don't think this is a battery issue (but not positive), but perhaps more a charging issue from the Prius - and it's not wrong to charge at 14.1V, but the battery should hold a charge closer to the 13.3V, and not be down at 12V after sitting 8-10 hours. So, there may be higher current draw sitting in the Prius than a 'normal' car. I am speculating on this, but there is a reason the battery is does not have a steady state voltage of closer to 13V. Every battery I've had, deep cycle and regular, has always had a 13V (about) charge after sitting a while. The battery I pulled out of my Prius, the original battery, read 10.2V as a steady state reading, after sitting for 10 hours. This was too low (but the battery was working fine for years like this), but I wonder if it's because the battery is not being charged correctly. I now have this battery on my bench in the garage, I've charged it with a deep cycle charger, and it reads 13.1V steady state after 10 hours of no charge. This tells me this battery may be 'fine', and I plan to put it under load and test soon. I expect this 6 year old battery to hold up under load - which will tell me the Prius is not charging it properly. I recall reading the Hybrid battery charges to 80% of the full charge and it can discharge down to 20% of it's capacity. This was done to not over-charge, or over-discharge, the hybrid battery and add longevity to the battery. It's a good practice but if the 12V battery is being regulated in a similar manner, these batteries were not made for this, and it's never fully charged by the car. I suspect this may be the case, causing failure of the 12V battery sooner than expected. This is my own theory and I'm looking into this more.

I just installed this in my wife's 2010 Prius. It will be 4 years old next month. Living in Arizona and the heat, I change out batteries at least every 4 or 5 years. This is a very simple project for the 2010 model. Do your self a big favor, when you change out the battery, use alligator clips with a 9 volt battery (yes, the kind you put in smoke detectors) connect to the power cable under the hood, ground it, then connect to the 9 volt battery before you change out the battery. It will keep your GPS and radio settings in tack. Then change out the battery, and you are ready to go. It was a simple operation, and what I have read is a much better battery then the factory install. My Toyota dealer wanted $350 + tax to install a new battery. My Optima did not come with a factory date, I wish it had. I do not know when it was made. Only fault I see with this purchase. Save yourself a lot of money. I can't attest to the quality of the battery until it is used for several years. My Mechanic highly recommends Optima batteries.

Put into a 2010 Toyota Prius. Installation was a two stage process. Step 1. The most important thing is to make sure you can get the rear hatch open, which requires the battery to be in place. This makes your job immensely easier. So I smartly jumped the car using the posts under the hood, and then opened the hatch and took out the battery so I knew which one to replace it with, and ordered this one on Amazon. No big deal, anyone with any mechanical aptitude at all can change the battery easily with a couple of metric sockets. It was in the rear trunk area, under several layers of easily removable parts, behind the rear passenger side fenderwell.But then I screwed up and didn't hook up the old battery again, so when the new one came, I couldn't jump the car to open the rear hatch. This was really annoying, requiring me lift the heavy new battery in from the rear passenger door and hook it up to the cables. Only then could I power up the car, open the hatch and finish installing it.Do yourself a favor, assuming that your battery is dead and you are ordering a new one from Amazon and can do without the car for the time it takes to ship the new battery to you. Remove the battery, figure out exactly which one you need, put the battery back into the car and hook up the cables to it and wait for the new one to come. Then jumpstart the car, open the hatch, and swap batteries. It'll save you some time and aggravation. Or leave the hatch open and park the car in a garage while you wait.