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Dec 30, 2017, 04:53 AM
Registered User
Bookstar75's Avatar

Electronics Questions

I am hoping someone can teach me how “voltage/amps” works and what a “bec” is used for and how it plays into the electrical system. My question is wanting to know if a specific size lipo battery is able to handle all the electronics needing power on a particular airplane setup including FPV electronics.
Here is my example: I have a small delta flying wing that runs off a 2 cell 3200mah lipo, I have a 10 amp ESC with a 2 amp BEC, I’m running only two small digital servos, a small scorpion motor, a spektrum 400 receiver, along with a Runcam micro camera, and a Tramp VTX for my FPV gear. I have the FPV gear wired to the ESC so my 2 cell battery is powering everything.
So my questions:
1. How do I know if the battery is capable of handling the electronic voltage/amp load? How do I calculate?
2. What is BEC and how does it work/purpose?
3. Example...the Tramp VTX says it’s a 6-18 Volt vtx. What does this mean? How do I calculate that into my overall total volts/Amps the whole electronic system is using/needs?
4. How will I know if I need another battery in order to supply power to some of the electronics so as to not overload the lipo battery I’m using?

Thank you 👍🙂
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Dec 30, 2017, 07:06 AM
Registered User
In simple terms it all comes down to those components that are sensitive to voltage variation and those that are not
The motor driving your small Delta is not voltage sensitive indeed its speed is regulated by switching the battery on and off very rapidly by the ESC. This causes the battery voltage to rise and fall slightly as it does so
Your RC receiver and the micro camera on the other hand are very voltage sensitive (and the servos as well to a slightly lesser degreel) so they all either need their own independent battery or a "protected" voltage supply from the main battery through a BEC which stand for a Battery Eliminator Circuit.
Your Tramp VTX appears to have its own voltage protection built in so may be happy to be directly connected to the main battery.
I believe you are actually powering the receiver and thus the servos from the BEC side of the ESC (with most setups it would be difficult not too!) and I presume you have the Tramp VTX directly connected to the LiPo.
As far as the 3200 LiPo is concerned it has more than capable of providing the power required to drive everything.
If you are worried about the LiPo I suggest you invest in a Watt meter. It will tell you how many Amps are being drawn from the battery at full power and from that you can determine how long it is safe to fly before you are likely to damage the battery.
Most ESC provide some protection in that it cuts the power to the motor before the battery is too depleted leaving you enough left to at least control the plane to land it.
Dec 30, 2017, 12:33 PM
B for Bruce
BMatthews's Avatar
You should really look into some sites that teach you about basic stuff. The scope of your questions is basically asking us to write you a book to cover it even half way.

I will offer this to you. If you understand about plumbing for water in terms of pressure and gallons per minute it may help you understand about electricity.

Voltage is like pressure. And the devices you use are rated to work with that much "pressure". Hence the range of 6-18V for your VTX. Not enough and it won't run. To much and it'll "burst" in some way you won't like.

Current in amps is very much like "gallons per minute". Or if you understand compressed air tools think of it as cubic feet per minute.

The BEC as mentioned above is a "pressure regulator" included in the ESC to drop the voltage (pressure) down to a value that the receiver and servos can use. But it has a limit on how much you can draw from it of 2amps. That is good enough to run the Rx and servos provided you are not using any big high power servos for special options. Or that you are not running a large number of servos for both flight controls as well as camera gimbals or similar uses.

Depending on the components you use some of them will be able to run directly off a battery pack and some may need an extra regulator. Or you may need an extra regulator to run the extras because you really should not connect anything other than the control Rx and servos to the onboard BEC of the ESC.

To figure out how much output you need for the regulator you need to find data on the draw current for each of the devices you will run on the regulator powering the extra stuff. Add all of the numbers up and then add another 50% of that value for safety and that is the minimum supply current rating for the extra regulator you want to obtain.

Watts is calculated by V x I = W. In electronics V is volts and I is current because "A" is used in the math for something else already.

This reply is really just a small glimpse at the whole picture but it's the direct answers to what you asked. To get a better appreciation for it all I really suggest you search online for "basic electronics tutorial" and read up a few of them. Otherwise when you start doing more than what you want to do know you will only have about 1/10 of the whole picture.
Jan 01, 2018, 07:55 PM
Registered User
Bookstar75's Avatar
Thanks guys! I appreciate the help!!

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