Will optima battery fit?

You can, you will need an adapter kit

Installation Kit for Optima battery in Prius

 

The 12V battery for the Classic Prius has the positive terminal on the right side, when the battery is positioned so that the terminals are closest to you. That is the reverse of what is needed for 2G Prius where the positive terminal needs to be on the left side.

If you install the battery so that the battery terminals are where they need to be, they will be quite close to the fender which poses a potential safety hazard if your car is hit in that fender.

 

Patrick,

Will the Optima Yellow Top that is being sold that fits the Gen II Prius work without any sort of kit? In other words, can you use the existing OEM cables that came with the Gen II Prius originally?

I was under the impression that the Optima's being sold today have the small posts with the orientation of the posts in the correct placement (negative close to rear of car and facing towards center of car). But now I am not sure about all of that.

Thanks for all of your help here on Prius Chat!

 

Optima DS46B24R Optima battery direct fit replacement for Prius 2004 + , Prius V & Plug-in Prius with Instructions is a direct fit for Gen 2, Gen 3, PiP, and v.

D51R needs the kit to fit in the Gen 1
D51 uses the same kit to fit in Gen 2. As Patrick says, it has the poles at opposite ends, so is less safe in a collision. But it will work.

 

You can buy a direct fit battery from Napa, either a Napa brand or the Optima Brand. Both have the pencil posts and vent holes.