Project needs battery/brushless 5v motor advice

[anti_hero]

Hello, I am currently engaged in building a prototype. The main problem I am having is my battery running out of juice too quick. The main component is using a 5v brushless motor. I dont know much about batteries and I have been using a standard 9 volt in my rough prototypes. I need between 2 to 4 hours of run time to make it viable and so far I have been able to eek out 45 mins on a fully charged 9 volt. I have also been looking into rechargeable battery packs like the ones in cell phones and even the ones that are like 5 AA wrapped up and put out 6v. My question is what type of battery should I be using for battery life to get me as close as possible to my goal with out going bigger than say 5 AA's or two 9 volts. I realize that battery life alone will not get me to my goal and i am researching using a smaller and more energy efficient 5v brushless motor.

 

Thanks!

 

"anti-hero" FOB Liberty, Iraq

[Spyman]

There are losses involved in regulating a 9V battery's output down to 5V and if not regulating it down a motor made for 5V will use a lot more juice.

 

I think this site might be helpful in choosing batteries: http://www.solarbotics.net/library/pieces/parts_elect_pass_batcomp.html

 

If for example a Alkaline AA battery has a capacity of ~2800mAh and you want to run the motor for 4 hours then the motor can't use more than 2800mAh/4h=700 mA while running.

 

If the motor is bigger/uses more than 5V*700mA=3.5Watt, you need more batteries in parallel.

 

Have you tried running the motor on 4.5V ?

 

Lowering the voltage also lowers the current and gives longer duration, but less power.

 

For example with 6 AA Alkaline 2 parallels of 3 in series you have 3*1.5V=4.5V & 2*2800mA=5600mA.

 

Which gives: 5600mAh/4h=1400mA and 4.5V*1400mA=6.3Watt.