# Electricity generated using an armature

1. Nov 16, 2005

### stu1984

Is there an easy equation to calculate the energy generated from spinning an armature. I was wondering if there was such an equation where I could enter the following inputs:
• number of rotations on the shaft
• the number & size of the magnets being used
• the length and thickness of the wire surrounding
…to get an output of the energy generated.

Ultimately I want to understand if it is possible to re-charge a battery (battery to be decided on) with electricity generated from this process.

Or if there are any useful websites or books anyone knows of

All information will come gratefully, I thank you in advance.

Regards

Stu

2. Nov 17, 2005

### Cliff_J

You will have a few factors that determine the generation of electricity, starting with:

Strength of magnets
Distance from magnets to coils
Number of windings in coils
RPM
Wire gauge in coils

The first two are quite important and going to be difficult to plug into a simple equation. The strength is going to fall off on an exponential curve based on distance.

In order to charge a battery, you need to maintain a voltage higher than the no-load float voltage. As you increase this voltage more then more current will flow into the battery and charge it faster while also heating it (via the internal ESR). But this is similar to the discharge curve where its not a linear relationship.

It would seem to be far easier to build a test rig then to try to calculate and end up off an order of magnitude from a poor assumption.

3. Nov 18, 2005

### stu1984

Thank you,

i am currently trying to asemble the components for a test. this will bring the result hopefully required to charge a battery