7 3/8 x 9 1/4 T echnical / Build Your Own Electric Vehicle / Leitman / 373-2 / Chapter 8
CHAPTER
8
Batteries “More than 85 percent of an average car’s gasoline energy is thrown away as heat.” —Dr. Paul MacCready, Discover, March 1992
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oday’s batteries, motors, and controllers are all superior to their counterparts decades ago. Contrary to those who say you’ll need a different type of battery before EVs are suitable at all, today’s conventional lead-acid batteries of the deep-discharge variety are perfectly adequate for your EV conversion. (Note: While lithium-ion batteries and nickel batteries are being used more readily, this chapter will focus mostly on lead-acid.) Improved lead-acid batteries are routinely available from numerous suppliers at a good price. Assuming a proper system design, if you install batteries correctly and maintain them conscientiously, you don’t have to worry about replacing them for tens of thousands of miles. Future batteries will be lighter and more powerful, but can hardly be more convenient than they are today. In this chapter you’ll learn about how batteries work and the language used to discuss them. You’ll be introduced to the different battery types, and their advantages and disadvantages. Then we’ll look at the best type of battery for your EV conversion today, the lead-acid type used in Chapter 10’s conversion, and look at probable future battery developments.
Battery Overview Your EV’s chassis involved mechanical aspects, and its motors and controllers dealt with electrical ones. Its batteries will now take you into the chemical area. While there are all sorts of battery developments going on in the labs, the objective here is to give you a brief battery background, and introduce the lead-acid batteries you’ll be working with on your EV conversion. Many good books about batteries are available both at introductory and the more advanced levels for those who want more data. Because your EV battery pack—a collection of 16 to 24 6-volt (or 12-volt equivalent) individual lead-acid batteries—represents the single largest replacement cost item, and quite possibly is also your largest initial expense item, it’s worth spending some time learning about batteries so you can choose and use them wisely. Batteries are the life’s breath of your EV, and every EV converter should be familiar with them on three levels. To graduate from battery class you need to: • Understand what goes on inside a battery
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