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Does a Solar Panel With Different Amounts of Milliamps Affect How Fast the Motor Moves?

You can use a solar panel's power to run a host of equipment, including electric motors. When choosing a motor and solar panel combination it's important to match the voltage closely and have a current rating that exceeds what the motor needs. Excess current capacity will not affect motor speed, although an insufficient number of milliamps makes the motor run slower than its rated speed.

Solar Panel Output
- Solar panels produce direct current; the total current and voltage depends on the number of cells in the panel and how they're wired together. Tiny panels, such as those found on solar calculators, put out minuscule voltages and currents -- too little for a motor. A small panel, the size of a book, produces enough current to run the type of motor used in toys. Midsized panels put out between 6 and 24 volts with about 3 amps of current; this is enough to run a motor to pump water, open doors or perform similar tasks.
Motor Speed and Voltage
- To drive a standard direct current motor at different speeds, you normally vary the supply voltage within a limited range. The motor typically has a nominal voltage and speed that is is optimum for it's design. The relation between speed and voltage is fairly proportional, but beneath a certain minimum voltage, the motor stalls, and much above the rated voltage you expose the motor to excessive mechanical and electrical stress. Increasing the voltage also increases the motor's current consumption. If a solar panel cannot supply enough current, this effectively limits the motor's speed.
Suitable Motor Types
- Standard direct current motors are the only ones that work directly with the DC output of a solar panel. Stepper motors, which rotate a fixed number of degrees per input current pulse, require special high-power digital circuitry to drive them. Synchronous or induction alternating current motors work with a high-output solar panel connected to an inverter, but cannot use DC.
Voltage Regulation and Battery Backup
- If motor speed is important, you must control a solar panel's output with a voltage regulator and battery backup. The panel's direct output varies considerably due to weather and the sun's position in the sky. The battery stores the panel's current, providing a more reliable stream of power when the panel's output changes. The regulator keeps the voltage at a fixed value, allowing the motor to run at a steady, predictable speed.

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