HINTS & TIPS

Lithium Polymer Battery Safety Advice. 

Please click here for the latest advice offered by the British Electric Flight Association on the safe use of Lithium Polymer cells.

Fuses

Use of a suitable fuse is almost essential in any Electric Flight model. It serves to protect the whole power system against short-circuits and could save your motor or model from a total disaster!

Most common types of fuse are not suitable for Electric Flight as their resistance is too high. The only commonly available type which is suitable, is the blade types of fuse intended for automotive use. In order to minimise circuit resistance, it is well worth using the correct type of fuse-holder. This will also enable the fuse to be made easily accessible and can allow it to double as an arming switch.

What value of fuse to use? Basically, the lowest value which does not blow when the motor is started. Use of too high a value is almost as bad as using no fuse at all! Remember that a 10 Amp fuse requires almost 20 Amps to blow it!

Where to fit the fuse? Best place in the circuit is as close to the battery as possible, in the positive lead. Some modellers even incorporate the fuse into the battery pack itself in order to provide added protection during handling. If you are using a BEC system, it is vital that the fuse is connected between speed control (or switch) and motor.

BEC - Battery Eliminator Circuit

To the newcomer to Electric Flight, the term 'BEC' can be rather mystifying - let's try and enlighten you a little. BEC simply means that the speed control or flight-switch incorporates a voltage regulator which enables the receiver and servos to be powered from the flight (motor) battery. This may seem like a good thing for all models as it saves a few ounces of weight. However, all is not sweetness and light and there are some pitfalls to be aware of.

Firstly, BEC systems are only suitable (normally) for use with battery packs of between six and ten NiCd cells. Secondly, the BEC system can only deliver a certain amount of power, thus it is not advisable to use it with more than three servos or in larger models. Thirdly, the battery can only contain a certain amount of power, thus duration on the glide may be limited.

The one large advantage that BEC systems have is that you don't have to remember to charge receiver batteries anymore!

It is ESSENTIAL that ONLY BEC speed controls specifically designed for use in aircraft are used. These types will cut the power to the motor when the battery gets low and allow a safe amount of time for a gliding landing to be made. Some car and boat types of motor controls may not offer the same facility.

Don't forget that a battery pack under heavy load may be more likely to fail. Thus, restrict the use of BEC to those models which really need it (Speed 400 types) and use a receiver battery on larger models.

To BEC or not to BEC? It all comes down to personal choice. use the system that makes YOU feel happy

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