Protech ZOOM 425 ccpm Specifications download pdf (Page 194)

rpm of headspeed at 25% throttle and draws an average of 18 amps of current, then the ESC

and battery are actually supplying 72 amps of current for 25% of the time!

Therefore, if you use a motor with a very high Kv rating and you are forced to use a low throttle

setting to compensate for the high Kv, this will increase the load on the ESC and battery. In ex-

treme cases, this will shorten the life or destroy the ESC and/or battery.

30.1.11. How batteries work

A battery is basically a electrochemical device which stores electrical power.The closest phys-

ical equivalent to a battery is a water tank, which stores water.

Batteries have several important characteristics:

• Voltage (volts). Voltage is an electrical term which describes the force of the electrical pres-

sure.

This is similar to the pressure in a water tank. The higher the water pressure, the more wa-

ter will flow through a pipe connected to the tank. Similarly, the higher the voltage, the more

current will flow through wires (with some constraints).

• Capacity (maH). The capacity of a battery is measured in milliampere-hours, or maH. One

thousand milliampere-hours (1000 maH) is equal to one ampere-hour (1 AH).

One milliampere-hour is the ability to supply one milliamp of current for one hour, or two

milliamps for 30 minutes, etc.

• C rating. The C rating describes the maximum instantaneous (burst) power that a battery

can supply. A battery rated for 10C continuous discharge is capable of being discharged at

10 times its rated Capacity, or in other words, it is capable of being fully discharged from a

fully charged state in 60/10 or 6 minutes.

So, a 2100 maH pack rated at 10C continuous can supply approximately 2100 milliamps *

10 = 21,000 milliamps (21 amps) for six minutes.

• o Pack configuration. This is typically described as 3s1p or 3s2p, etc. The number before

the "s" denotes the number of cells in series, and the number before the "p" denotes the

number of cells in parallel.

So, a 4s2p pack of individual 3.7 volt 2100 maH cells would have a total voltage of 11.1

volts, and a total capacity of 4200 maH.

30.1.12. How motors work

A motor is basically a mechanical device which converts electrical power into a rotary mechan-

ical force.

For the motors used in R/C helicopters, there is a permanent magnet and an series of coils of

wire (called the motor windings) which act as an electromagnet. The windings are pulsed on

and off to sequentially push on the magnets, and either the magnets or the windings are at-

tached to the motor shaft which makes the motor turn.

(Note that there are some motor types which do not have permanent magnets, such as induc-

tion motors, but these are not used for R/C helicopters and will not be discussed here).

The part of the motor which is stationary is called the stator. The motor mount is part to the

Technical Appendix

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Protech ZOOM 425 ccpm Specifications Page 194