




One unit of your battery pack is a cell – it is only when you put several cells together that you have a battery – and each cell is nominally 1.2 volts (or 3.7 volts for LiPo). Our batteries are usually hooked up in series (positive to negative to positive etc.) which means that the voltage of the pack is 1.2 volts multiplied by the number of cells. e.g. 1.2 volts x 7 cells = 8.4 volts For LiPo 3S means 3.7 volts x 3 cells = 11.1 volts. Volts is a measure of the electromotive force or electrical pressure that you battery is capable of producing. The more volts you have (pressure) the more work you can do with it. To test this out, take a standard motor (say, a Speed 400) and attach a 7.2V battery to it and note the sound it makes. Then attach a 12V battery and notice how it goes much harder. If you measure the amps, you will see that they go up slightly with the extra Volts, but not much because there is no load. Amps. The result of this pressure is current flow – connect cable to your battery, connect it to a motor and the voltage rushes out of your battery. The rate at which the voltage rushes out is measured in amperes (AMPS) or milliamperes (mA), which are one thousandth of an AMP. The higher the AMPS figure the more current there is flowing and your battery will be empty sooner. It's a bit like emptying the petrol tank in your car  the faster you take out the fuel, the sooner it will be empty. The capacity of a battery (which is your tank of fuel) is measured in milliamp/hours (mAh) or amp/hours (Ah). If you have a 1200 mAh (or 1.2 Ah) battery, and you draw 1.2A of current from the battery, it will take one hour to go flat. If you double the current consumption to 2.4A, it will be flat in 30 minutes. 4.8A and it will be flat in 15 minutes, and so on. In LiPo terminology, the capacity of your pack is named "C". So, in the first example with a current draw of 1.2A for a 1.2 Ah battery, the current draw is 1C. Double that to 2.4A and it is 2C, and so on. To increase the current draw (increase the amps), you increase the load on the motor. The amp draw is governed by the load. Fit a bigger prop and your amps go up, fit a smaller prop and the amps go down (all else being equal). If you want a longer motor run, without changing your prop or number of cells, fit a larger capacity battery pack. That's like fitting a bigger tank! You can actually increase the voltage that you apply to a motor, and reduce the load (fit a smaller prop) and have less power than you started with. You can have high voltage and low amps, or high amps and low voltage and the power can be the same! When working on a power setup, you need to consider both Volts and Amps. 
