power drain too much

[Queequeg QuintParticipant @queequegquint38270]

[Queequeg QuintParticipant @queequegquint38270]

My battery is 12 volt, 12 AH.  ESC is 20 amp Mtroniks marine.  Motor is MFAComo 500 with 2.5:1 gearing.  Running great.

 

My radio receiver is a futaba 7 channel.

 

I got a cooling fan running off the BEC for the ESC and another cooling fan running off the BEC as well for the motor.  Also got 7 lights plugged into a switch, likewise running off the BEC.  So all these accessories are plugged into the receiver, receiving 5 volts from the receiver.  The ESC and motor get 12 volts from the battery.

 

When I turn the lights on, they are bright, but then a few seconds later they start to dim and fliker a little and the fan speeds drop dramatically.  But if I unplug the cooling fan I’m using for the motor, the lights will stay on steady & bright, and the ESC fan will stay at full throttle.

 

This leads me to think I’m drawing too much power from the BEC.  I dont’ really want to use a separate battery source for the fans because I really need to keep the weight on my boat as little as possible.

 

Is there any way to solve this problem?   

[Charles OatesParticipant @charlesoates31738]

you could try one of the fans from a scrap computer. These are designed for 12 volts but will work on much less. The advantage is that they draw a tiny amount of power, probably less than 100 ma at the voltage you will have. Trying to draw too much power from you BEC risks damage to the receiver.

  Another posibility is to reduce the power drawn by the lights, if these are not LEDs you might consider changing them as LEDs also use very small currents.

 Chas

[glennParticipant @glenn]

I would advise against using the BEC for anything other than supplying the receiver. There are several voltage regulators available, personally i would use a lm317 voltage regulator chip. Dont worry if you are not electronics minded , the cuircuit is very simple. 

Have a look here http://www.reuk.co.uk/LM317-Voltage-Calculator.htm  this should tellu all you need to know. If you got any questions get back to me

cheers Glenn

[Dave MilbournParticipant @davemilbourn48782]

Why don’t you fit an additional BEC? They are much smaller than an extra battery and will supply 1A quite happily from that big SLA lump. 

A suitable built one can be found here:

http://www.action-electronics.co.uk/pdfs/P19.pdf

Dave M

 

[Queequeg QuintParticipant @queequegquint38270]

What is an “SLA lump”?

[TelstarParticipant @telstar]

SLA   Sealed Lead Acid   battery

or you could use a 12V fan direct off the main battery

 

Edited By Telstar on 03/06/2009 16:59:28

[Queequeg QuintParticipant @queequegquint38270]

I put the motor coling fan on a sepearate 9-volt battery, and that works fine.  But I still have a 5volt computer fan for the ESC attached to the BEC.  Everything been working fine, no problems.  I installed a second servo to rotate a small digital video camera, and when I move that forth and back the lights flicker a bit, but not much.  Is it possible, over time, to damage the BEC on the Futaba radio by running 2 servos, one ESC, 6 lights, and one fan (all plugged into the receiver for power and control)?

[60wattParticipant @60watt]

I doubt you have got a bec regulator on the receiver,since it is seven channel.
The bec (on the speed controller?) is possibly cutting out which causes the light to flash.
 

I think you should take Glenn’s suggestion and go to the reuk site but use the constant current circuit for your lights.If you divide your lights into equal branches you would only need a single LM317 and current setting resistor for say 3 branches of two series connected white leds.I think you should remove the fan from the bec supply as well.

 

Ten pence constant-current led driver

On my diagram there is a single branch containing four leds in series ( you wouldn’t get four white leds running from 12 volts).It is slightly more complicated than an LM317 + resistor but if you go to Maplin the bill is still a few pennies.The voltage loss across the transistor and R2 is smaller than the LM317 AT < 0.9 volt.

Edited By 60watt on 02/07/2009 21:00:47

[shipmate60Participant @shipmate60]

The  BEC will only supply 1 amp reliably,

If you overload it you will get the symptoms you describe,

The BEC is designed to run ESC and 2 servos reliably.

Bob 

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