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# Simple 6th Grade Project - Solar Panel and DC Battery

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#### itchibahn

##### New Member
I got a 2.5W 5V/500mAh solar panel, which reads 5.7V under a full sunlight, and a 3V-12V DC motor, which someone said in a comment that at 3V no-load takes 35-40mA. If I wire the motor directly to AA battery reading 1.23V, it spins fast. But when wired directly to the panel, it won't spin at all. Please help... Two parts are below. Thanks.

Solar panel: https://www.amazon.com/gp/product/B00CBT8A14/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1
Motor: https://www.amazon.com/gp/product/B07GDP2FCL/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

The problem could be that the solar cell will not provide enough current to allow the motor to start.

someone said in a comment that at 3V no-load takes 35-40mA.
Have you measured your motor to see what current it takes?
Also, you need to be aware that when a motor starts, it takes more current than when it is running with no load.

the rating of 500mAh looks strange to me.
It is the rating which is often used to describe the capacity of a battery, it is the product of current in milli-amps and time in hours.
I do not see how that can be related to the output of a solar cell.
But then I am not an expert on solar cells.

Have you done a load test on the solar cell?
Use resistors as a load and measure how much current can be drawn from the cell and at what voltage?

Only when you KNOW the parameters of the cell and motor can a sensible estimate be made as to whether the cell can power the motor.

JimB

Thanks for a reply. I've connected my DVM in series with the motor and an AA battery, and it initially draws ~105mA then settles to ~38mA. The 500mAh is a typo, it supposed to be 500mA. It's a night time here, so I can't test it outside, but tried with 60W incandescent light. It read 4.9V 1mA with 220ohm resistor. I will try again in the morning.

Thanks for a reply. I've connected my DVM in series with the motor and an AA battery, and it initially draws ~105mA then settles to ~38mA. The 500mAh is a typo, it supposed to be 500mA. It's a night time here, so I can't test it outside, but tried with 60W incandescent light. It read 4.9V 1mA with 220ohm resistor. I will try again in the morning.

Solar cells are EXTREMELY inefficient - a number of years ago there was a UK Robotics Sports TV programme, and one of the events was a solar power sprint race. It was held indoors, and there was an incredibly large array of lights above the track to make it work - simulating bright sunshine takes an amazing amount of lighting, and many, many kilowatts.

Basically you use your solar panel to charge a battery, and then use the battery to power the motor. If you want to run it directly, you need VERY bright sunshine and a LOT more solar panels.

Solar panels are typically 10% efficient. Solar is about 1000W/qsm. Your panel is 0.15x0.13 M. So it could produce 0.19x0.13x0.1x1000 = 1.95W. However, this is in bright sunshine. You may need two or three to get it working.

Mike.

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