You will want to keep the weight forward if you can to keep
the vehicle balanced. Weight in the back tends to throw off
steering capabilities as we found out with one of our early
experiments.
You will just have to search around and find a place. If you
don’t need the extra space you might even consider a
backseat location? Either way you will have to build special
racks to hold the batteries securely. The closer the placement
to the motor assembly the less wire used too.
You can either box the batteries to protect them or you can
use some sort of removable cover.
You can locate your batteries within the frame assembly very
effectively if you have the room and the right batteries. Small
cars do not offer this capability usually.
You will have to have access, especially for lead acid batteries
which require monthly maintenance. Keep that in mind.
Please be careful that passengers are protected at all times,
no safety issues with the batteries.
You will probably want to consider the use of sealed batteries
if you are converting a car, as they are safer in the case of
accidents or with passengers close by.
You can also use the trunk space effectively with most
vehicles, although this cuts down on your hauling
capabilities. Most cars have more room than you thought, so
look around for the solution you are most comfortable with.