The most efficient and maintainence free battery for any vehicle ids called a "glass pack". I'm not sure what company makes them, but they have the best warrenty of any battery available and the longest life expectancy.

The conversion is easy But TAKE YOUR TIME Here's a web site
grassrootselectricvehicles.com

To answer the Largest deep cycle you can find. about $150.00 each many brands NOT SEARS NOT EXIDE blue top are the same GO TO A INDEPENDENT AUTO PARTS STORE AND ASK THE "OLD-MAN" BEHIND THE COUNTER. PLACES LIKE AUTO ZONE WILL SCREW YOU

The others have it right, but the Prius battery isn't designed for what you want and is very expensive. The Optima blue tops are good, but also pricey.

is this a trick question? How on earth can you convert your gas guzzling engine to run on electric? its impossible. You need an electric motor to drive your gears for this. I also wonder how on earth back in the late 1970's(I owned a 1979) you could buy a car getting 52 and 54 mpg yet today even these new dual types cars dont come close to that! I am referring to the volkswagon rabbit and dasher….but many others also got close to mid 40's to 50 mpg range back then!

Or, you can have an expert convert your car for you.

As to using hybrid batteries – sorry, they won't sell them to you. The NIMH batteries used in hybrids are wonderful for EVs, but the patents for those advanced batteries were bought by Chevron/Texaco, and now the licensing of those patents prohibits their use in pure electric cars. Absolutely true story.

Most conversions still use old 100-year-old lead-acid battery technology, which is relatively inexpensive (the battery pack in my EV costs under $1000) but your driving range will only be about 50 miles. Various vested interests have been able to put up roadblocks (like the NIMH situation) to more advanced batteries.

However, if you're a bit of an engineer, you may be able to get some new Chinese Li-Ion batteries. A few hobbyists I know of have been able to obtain and use these, but you'll have to design your own charging system (or get help from an engineer.)

Good luck!

dude I really don't think this will work

yes I would say the same,napa optima are the best,I use 3 blue deep cycle ,in my car hook together as I use a 900 watt inverter and have ac powers for a couple of hours when parked,the blue last for 1years half so far every day almost total discarge, the best thing about these battery are how fast they recharge on alternater power,half empty back to full charge in 5 minute idle yes,empty about 10 minute drive that alone is unreal, also coil battery have a stronger post inside and more surface area as a coil cost about 180.00 each but worth it.

Good luck with the conversion it will not be simple. I would look into a Optima Blue top battery. As the battery is designed for long steady amp draws. Unlike normal car batterys which are designed for a short high amp draw on startup. Like a electric outboard motor on a boat.