I have a speed controller (60A/BEC) which is currently used in a glider with
12 cells and 3 servo's. I want to use it in another glider with 6 servo's. Is it possible to disable the BEC and use an extra battery for the receiver in order to avoid that the controller becomes to hot and disconnects to protect itself ? If yes, how can it be done ?Fil, Belgium
It may be possible to disable the onboard BEC, usually just turning off the speed controls ON/OFF switch is taking the internal BEC out of circuit, BUT that depends on the ESC. See if there is any mention in the ESC's manual. There are aftermarket BECs out there that will handle that many servos with no problem or you can fly with a battery pack.
Jim
Yes. Simply cut the positive wire from the ESC to the receiever and plug a battery (or UBEC or SBEC) into a spare channel.
interference, always use a seperate batery for the receiver You won't even notice the difference in weight greetings A.Redert
On 5/20/2004 5:17 PM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:
If you look at the connector that plugs into the receiver you should see
3 wires. Unplug the wire that provides the power to the receiver and put a piece of tape over the end of it. The wire can easily be unplugged by using the tip of a #11 blade to gently lift the plastic hold down tab. The make of your transmitter/receiver will determine which lead is the power lead. By unplugging the wire rather than cutting it, it allows you to easily reconnect it if you decide to use the BEC circuit at a future date.It is not recommended to use the BEC with over 10 cells. For over 10 cells you either need to use a separate battery for the receiver or a UBEC (and leave the wire intact). The UBEC will be lighter in weight than a separate battery for the receiver.
MEC
That does NOT actually disable the on board BEC it just makes it so the ESC's BEC is just powering the ESC and not the full radio system. That may be acceptable. If the unit has an on/off switch having it in the off position usually disconnects the internal BEC from the electronics, usually......
Jim
| when using 12 cells its better not to use bec at al,
True ...
| bigger chance on interference
... but that's not why. The problem is almost certainly heat dissapation.
If you're putting 15 volts into your BEC and it's delivering 5 volts to your receiver and servos, that's 10 volts that's being turned into heat. If your receiver and servos are using 300 mA of current, that's three watts of power ((15 volts - 5 volts) * 0.3 A). It may not sound like a lot, but the power regulator chip is quite small and probably doesn't have too much cooling, so it'll get hot. Fast. If it gets too hot, the magic smoke will escape, and your plane will crash. (R/C planes need that magic smoke to fly. Let it out at your own risk!)
| > Yes. Simply cut the positive wire from the ESC to the receiever and plug | > a battery (or UBEC or SBEC) into a spare channel. | > | That does NOT actually disable the on board BEC it just makes it so the | ESC's BEC is just powering the ESC and not the full radio system.
That's true, but since the ESC uses very little 5v current (coming from the BEC), it's not really a concern. The heat generated by the BEC will be very minimal since the current is very minimal, even if the voltage involved is high.
| That may be acceptable. If the unit has an on/off switch having it | in the off position usually disconnects the internal BEC from the | electronics, usually......
In the ESC+BEC's that I've seen that have an on/off switch, the switch was wired to disconnect the positive wire. So there is no (electrical) difference between cutting the wire and turning off the switch.
In case somebody isn't aware, turning off the ESC switch is not a good way to turn off your plane (though it's probably ok for the walk from the runway to the pits.) The ESC is still powered, so it'll slowly discharge your battery, and I imagine that in an extreme case (extreme RFI perhaps?) it's possible (though unlikely) for the motor to roar to life, even with that switch off. Instead, disconnect the battery and be sure.
That depends on what wire you are talking about. Cutting the + lead from the receiver connection would still leave a hot ESC and BEC as long as the battery is connected and a much greater chance of RFI causing an unexpected motor run.
That is most cetainly true.
Jim
Not on any unit I have seen it doesn't.
Does on every JETI and FMA.....
In fact, I just looked at a FMA 50A w/BEC and the switch removes the output of the internal BEC from the internal electronics. SO.... if you just cut the red wire going to the radio you will still have a HOT ESC if the ESC switch is turned on which it would have to be because you cut the red wire from the radio that would now be supplying power to the ESC. It would be VASTLY better to remove said switch in its entirety (that way it is ALWAYS off) and use the add on BEC to power everything.
Name an ESC that is different.
Jim
I have not had much success with BEC over the years.
The trouble is many ESC's have too small a heat sink - and at part throttle some ESC's heat up more than on full throttle. So the regulator chip gets warm from the main FET's- and most regulators have thermal protection so they shut down - and so you then have no power to the Rx and servos. Friendly or what ?
C W
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