What kind of batteries should I use?
At the moment there are really only a few choices for EV batteries.
The first is flooded lead acid batteries, such as golf cart and trolling motor type batteries. While these are reasonably priced, they do require periodic water level checks and cleaning. Dollar for dollar they are the least expensive way to power an EV. For high performance EVs however, they are a poor choice, because of the weight, and inability to handle high current loads (over 600 amps) without losing service life.
A second choice is VRLA, (Valve Regulated Lead Acid) AGM (Absorbed Glass Mat). These are often used in computer backup (UPS) power systems. They are considered sealed, so there is no fluid level to check, and they stay clean, because they don't vent under normal charging. They are able to deliver astonishingly high currents without failing. They do tend to be a bit more expensive, and require more sophisticated charging systems than the flooded batteries. They also usually have a shorter service life.
Another choice is gel cell batteries. These are lead-acid batteries with the electrolyte in a gell format. Due to the methods used in manufacturing them they tend to be very consistent battery to battery within production lot. This reduces the need for the battery management systems used on AGM batteries, though many folks still recommend them on gells as well.
Yet another choice is nickel-cadmium batteries. These have become less available due to regulatory changes in Europe. They tend to be considerably more expensive than conventional lead-acid batteries, but their extraordinarily long service life make them actually less expensive over the life of the vehicle.
Lithium based batteries are finally starting to trickle though to the individual user, but so far not in large numbers. Their long term life span is still a bit of an unknown, though it is quite promising.
You may have heard about other types of batteries, such as nickel-metal, zinc-air, and many others. When they become available to the general public I will add them here, however, at the moment they are not available outside of test programs.