Using a dynamo to charge batteries

[narrcissuss]

Hi guys,

I’m a sophomore physics student trying to design a mechanically driven EAP actuator propulsion system and I’m stuck. First off my understand of electrical circuits is rather limited at this point but the design is relatively simply, here’s gist of it. The system is driven by the same means as a bicycle (pedals and crank) that attach to a dynamo generator to charge an array of batteries to power a circuit board causing the EAP to actuate. The portion of this I’m stuck on is the charging and discharging of the batteries. I’ve read some posts here and there and there seems to be a pretty strong argument for using a capacitor in place of a battery array but all the same I’d like to get some opinion on how to set up the battery array. The charging of the array seems rather simple setting up the charger to run off the dynamo but the process of discharging the batteries while they remain on the charger escapes me. Any info that would clear this up would be great.

 

[Nigel Goodwin]

How much power do the EAP's require? - it really depends entirely on that.

For any amount of power worth pedalling for, I would suggest batteries are the way to go - capacitors are really only suitable for very low powered tasks.

 

[narrcissuss]

Im working on a proof of concept on a smaller model so the power demands will be relatively low. If you feel batteries would be the best bet how could I allow them to charge and disspate from charging dock?

 

[Nigel Goodwin]

You need to be more specific about exactly what you're trying to do, available power from the dynamo, battery capacity, current drawn by the load. Any and all of those will directly affect any design.

 

[narrcissuss]

"You need to be more specific about exactly what you're trying to do, available power from the dynamo, battery capacity, current drawn by the load. Any and all of those will directly affect any design."

Ok, so sorry this has taken so long to reply to the project took a backseat for finals and break. Answering those needs in order: the dynamo is regulated with a maximum output of 3 watts, the battery capacity will be around 2200mAh, the current draw im told will be 100mA and the voltage needed will range 4-6volts.
The idea of this is that the batteries start off uncharged and as the dynamo runs a portion of power goes to charging the batteries and a portion goes to operating the EAP. (This to me seems like a lot to ask of a 3watt output but that is how i was asked to design it and my understanding of electronics are such that im not 100% it cant be done.) Once the batteries have been fully charged i'd like the system to "realize" that the batteries have been charged and shift all the output to running the EAP. Another requirement is that when the person running the dynamo gets tired they'll be able to stop pedaling and the system will shift from running off the dynamo to running off the battiers. This in a nut shell is what i'm trying to accomplish.