I am unable to find a definitive answer about whether the replacement battery available for the 2004 Prius will work for a 2003 Prius. Can anyone help? My 2003 still has the original factory model S34B20L, which is no longer available, and the replacement requires a $50 kit on top of the $170 dollar replacement battery. The 2004 was manufactured with either a model S34B20R or S46B20R, the second of which is available, but I am not sure whether it will work in my car. I'm really not thrilled about using the Miata battery with conversion kit, just because of the hassle, but that's the only alternative I can find besides the S46B20R.
S46B20R is physically longer than the S34B20L so it is likely that will not fit in your battery holder. Also, the battery terminal polarity is reversed (this is the meaning of R vs. L) so to make the battery work, you have to mount it so that the terminals are adjacent to the fender. This is an unsafe practice in the event that fender is hit in an accident and the positive terminal shorts to the inside of the fender.
When I owned my 2001, I installed the Panasonic 12V battery that Toyota dealers sell, using the battery bracket conversion kit. The S46 battery is probably an inch longer than the S34, I don't remember for sure. Maybe you could have your dealer order the S34B20R battery, if you don't want to buy a conversion kit for the Panasonic battery, and can live with the risk of having the terminals adjacent to the fender.
Take the battery out and measure the dimensions. Then shop for a battery that will fit within the same space. Bob Wilson
