[byte312]

Not a bad thought but, the more weight you put in the less the range. Putting more batteries in a car adds more weight. I think the solution is the correct battery and nothing more than what is required to power the motor at peak tourque. Just stop for lunch and rest the batteries. Effeciency is the inverse measurment of waste. If your motor weighs 150 lbs and is 80% effecient it wastes more than 20% of the energy available. If your motor weighs 50 lbs and is 80% effecient it will waste less than the first one but still more than 20%. This is because the motor must pull it's own weight. If you find a way to capture some of the waste energy and use it, you will come out ahead.
The Tesla switch was a circuit that always charged one battery through a motor with two batteries supplying a higher voltage in series. After a short time, the batteries were switched with vacume tubes so that two batteries always charged a third one. The energy was pasted back and forth through the motor. It worked but it required an extra battery which sometimes burst into flames.
I have built a cuircuit that works on the same principle but it uses air-core transformers and capacitors to store excess forward current, reverse EMF, and noise from the motor. Once stored in the capacitors, the waste energy is avalable to be used for any usefull purpose.
The power to weight ratio is important. always check your batteries and motors for the best ratio. For a battery, divide the watt hours (amp hour x volts) by the weight in lbs. The larger the number the better as this is the power per pound. For a motor. divide the horsepower or tourqe by weight.
I give away the schematics free to anyone who asks for them. I can send PDF files packed with info.