tailieunhanh - McGraw-Hill - The Robot Builder's Bonanza Part 7

Tham khảo tài liệu 'mcgraw-hill - the robot builder's bonanza part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 196 ALL ABOUT BATTERIES AND ROBOT POWER SUPPLIES FIGURE Discharge curves of a 1-AH battery at three- five- and seven-hour rates. FIGURE The charge discharge curves of a typical rechargeable battery. Note that the charge time is longer than the discharge time. Ni-Cads provide different nominal cell voltages. Specifically Ni-Cad and nickel metal hydride batteries provide volts per cell and lead-acid batteries provide volts per cell. To achieve higher voltages you can link cells internally or externally see the next section Increasing Battery Ratings for more information . By internally linking together six cells for example the battery will output 9 volts. Nominal cell voltage is important when you are designing the battery power supplies for your robots. If you are using cells a four-cell battery pack will nominally deliver 6 volts an eight-cell pack will nominally deliver 12 volts and so forth. Conversely if you are using cells a four-cell battery pack will nominally deliver volts and an eight-cell pack will nominally deliver volts. The lower voltage will have an effect on various robotic subsystems. For example many microcontrollers used with robots see Part 5 of this book are made to operate at 5 volts and will reset restart their programming at volts. A battery pack that delivers only volts will likely cause problems with the microcontroller. You either need to add more cells or change the battery type to a kind that provides a higher per-cell voltage. BATTERY RECHARGING 197 INTERNAL RESISTANCE The internal resistance of a battery determines the maximum rate at which power can be drawn from the cells. A lower internal resistance means more power can be drawn out in less time. Lead-acid and nickel metal hydride cells are good examples of batteries that have a very low internal resistance. When comparing batteries you don t really need to know the actual internal resistance of the cells you use. Rather .