A BEC is used to eliminate the wt of an extra airborne battery. What is the recommended setup if you want to use the extra battery for the controls?
My Gilmore crashed on Sat. Takeoff was good, aircraft levelled off and as I banked rt, ac dropped it's nose and plummetted to the ground. Not pretty! Anyway there was no reaction from the controls, could not pull out/level off.
While gathering the bits and pieces, I noticed that one of the wires was off the esc. I suppose it could have pulled off in the crash, but i think that it came off in flight, and that's why I couldn't get the plane to pull out/level off.
So I have decided that on the larger planes where a couple of oz. won't make much difference, I'll add an airborne battery pack which will ensure full control.
Any thoughts/suggestions would be greatly appreciated.
Bigstik
My thinking about when or when not to use a BEC is as follows:
Separate RX batteries need to be monitored and charged and are generally a pain in the butt. However, they are important to use in several situations:
- When you are drawing huge amounts of current from your main pack the voltage drop on the pack can cause the BEC and RX to brownout. Some RX systems (like spektrum) take a long time to reboot thus extending the brownout.
- When there is potentially noise coming from the ESC you want to use an optocoupler and RX battery to separate the RX electrically from the ESC (more of an issue with 72Mhz).
- Some ESCs will only allow you to use the BEC circuit when flying with a low cell count (was more of an issue with older ESCs, now they almost all have switching BECs)
In all other cases I use a BEC.
From your short description it sounds like you suffered a possible brownout on the RX, or a range issue. Was it a 2.4Ghz system? It's terrible to not know what went wrong and to be left guessing.
Ben
After my little fire incident in the Nexstar....I was VERY happy to have the battery. When the ESC was on fire...and the plane was starting to catch...I was still able to land it an bring it to a stop within reach to put out the flames. 8)
I have been looking into backup battery solutions. The cheapest is just adding a forward biased diode to the positive lead of both the ESC and the battery...You should have a minimum 5 cell reciever battery since it will loose .7 volts to the diode, and the BEC should be a bit higher voltage than battery. You will need to add the diodes somewhere that still allows you to charge the battery. This way...any shorts on either side will not affect the backup from working.
I plan to test all of this over the winter...Stay tuned for the results :)
Steve
Still looking for an answer! If wt is not a concern, is one better to power rx and servos with a separate battery? If main motor battery goes south, one still has control of the airplane correct? If so, how does one set it up?
Bigstik
If you want to only use a seperate receiver battery, check with the manufacturer of the ESC on how to disable BEC...Most units get you to disconnect the red (positive) wire going to the receiver from the BEC/ESC and connect the battery to a free channel or battery port on the receiver.
That should do it.
Steve
Quote from: jabiggerstaff on August 28, 2012, 07:35:23 PM
Still looking for an answer! If wt is not a concern, is one better to power rx and servos with a separate battery? If main motor battery goes south, one still has control of the airplane correct? If so, how does one set it up?
Bigstik
Well, if you're asking how to install a bec that's simple. Connect it to the aux port in your rx and power with a 2S lipo. Make sure you're using an opto esc, or as Steve said disconnect the red wire if using a regular esc.
I don't want to eliminate the battery, I want to add one. Very confusing.
Is it a simple case of removing the red/signal wire from the esc connector?
Bigstik
What ESC are you using? I just don't want to give you advice without manufacturers approval.
Steve
Alan,
If your ESC does NOT have a built in BEC then treat it just like a throttle servo in a glow plane. You'll need a separate Rx battery with a switch to power your onboard radio.
If your ESC has a built in BEC, pull or cut the red wire from the plug leading to the Rx (from the ESC) and tape it back so it doesn't short on anything. Now your ESC is acting like a throttle servo in a glow plane. You've disabled the BEC. The ESC will still function as usual.
Robert