I currently have a 3 cell 11.1V 1800mah Li-Polymer Battery that operates a Brushless Outrunner Motor (700kv) with 25A Brushless ESC. How do I know what size battery is next? and how do I determine the max battery for motor? Please give any other info that would be helpful. Thanks in advance.

Paul

Put it on an airframe and fly it using one of the suggested prop sizes. Evaluate flying performance against what you are looking for. Try a more aggressive prop for more power and be sure to check amps/watts with a watt meter to make sure you wont go over the limits of the esc and motor. That setup should be a good starting point. If your flights only last a short time, you might want to go to a larger battery.

I bought the common sense RC lipo fuel gauge which my hobby guy said is a must in electric flying. And I am using a 11x4.7 blade. I was going to try 5 min flights and judge it on that. But is there a formula for how to get to say a 4 cell with longer flight time. I know I have to keep size and weight into factor.

Hi Paul -

If your goal is more flight time, you need a battery with larger capacity (mAh). For example, if you switch from a 1800 mAh battery to a 2500 mAh battery, your flight time will increase.

If you were to switch from a 3-cell to a 4-cell battery, you must be careful. Your motor or ESC may not be able to handle the higher voltage of a 4-cell battery. In addition, if you switch from 3 to 4 cells without using a smaller prop, you might exceed the maximum power rating of the motor. In summary, increasing the number of cells requires knowing if your motor and ESC can handle the greater voltage and possibly changing the prop.

Staying with 3 cells and increasing the capacity (mAh) will give you greater flight time without damaging anything. The battery with the higher capacity will probably weigh a bit more than your original battery, so you must be sure your plane can carry the extra weight.

- Jeff

Thanks Jeff,
That helped alot. And since I have you on the subject. How do you know what a electric motor can handle? as well as the ESC? Thanks again!!!!!!!!!!!!

The manufacturer of the motor should list a maximum current rating (Amps) and/or a maximum power rating (Watts).

For the ESC, the manufacturer should list the maximum voltage (Volts), although this is sometimes given in terms of the maximum number of cells (2 cells, 3 cells, 4 cells, etc.). And every ESC is also rated for a maximum current (15 Amps, 25 Amps, etc.).

You should never exceed the maximum ratings for either the motor or the ESC.

Batteries also have maximum ratings. If you try to draw too much current (Amps) from a battery, you can damage or destroy the battery.

In an ideal setup, all of the components are in a nice balance: the motor, ESC, and battery are all being operated within their maximum ratings.

- Jeff

Thank you MUCH! I will look into all the above.

EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC FLIGHT
http://www.rcuniverse.com/forum/m_7100376/tm.htm

Alot of info. I put it in my faves. Thanks