Hi, I’m a beginner at this so bear with me! For a university project, I need to connect 3 small fans in what I think would be a parallel circuit, to test a prototype. My knowledge of volts/amps etc is pretty much non existent. I thought the simplest thing would be to run them off a 9V battery, but what are the implications of running, say, a 5V fan off a 9V battery? Does it just burn out? Is it to do with current (in which case how to work it out?) Is there an extra component I can build in to the circuit? Is there a better solution altogether?
Be gentle with me, I’ve not looked at anything like this since school 25 years ago 
Thanks in advance
Hi,
The answer to your question will strongly depend on your fan type and voltage rating. We assume that you are using DC fans.
Usually, DC Fans are rated for a voltage range (since they are base on DC motors) and will work at different voltage levels. However, it will be more efficient at a given voltage.
This should be provided by the manufacturer of the fan in its datasheet. You will need to verify in your fan’s datasheet if it can be powered through 9V supply. If the voltage exceeds the recommended voltage range, you risk damaging the fan.
Current is a different aspect. A fan will consume a continuous amount of current while operating at a given voltage. For example, this 12V 2400RPM Fan - 3,62 “x 3.62” x 0.98" consumes 0.16A continuously at 12V.
Therefore, you should choose a power supply that can provide higher this amount of current continuously. For example, if you are using 3 fans and each fan consumes continuously 0.2Amps at 12V, you will need a 12V power supply that can provide at least 0.6Amps continuously (preferably higher to be safe).
