I feel like a kid heading to the toy store at Christmas. The Weak Signals annual event in Toledo, Ohio, is only a couple of weeks away!
If you’ve never attended the Toledo R/C Expo, it’s something you won’t forget. Nearly every manufacturer is represented, along with hundreds of vendors. It’s an opportunity to speak with some of the engineers and marketing people behind the scenes, not to mention shaking the hands of most members of AMA’s Executive Council!
If you decide to attend, be sure to bring an indoor model with you. There is an off-site venue in which to fly. There is also the indoor Electric Tournament of Champions (ETOC), where some of the world’s best pilots display their aerobatic prowess.
The annual auction, held in the conference center ballroom, is another great reason to go.
The Toledo Show is one of my favorite events of the year and I get to see many of you there, which makes it that much better. I hope you’ll attend.
External BEC Usage
You’ve heard the term, and you’ve probably used one whether you knew it or not. Battery Eliminator Circuits (BECs) are small devices that eliminate the need for a receiver and servo battery pack. They take higher voltage from the motor batteries and drop it to a level suitable for receivers and servos.
There are two types of BECs: internal and external. The internal BEC is built into the electronic speed control (ESC) and the external BEC is a separate unit that is wired into the battery connector circuit.
The benefit of using a BEC is not worrying about taking off with an uncharged receiver battery. The BEC pulls power from the freshly charged motor battery.
Always check your ESC to see what the limit of the internal BEC is. Most have it listed it on the label, but some manufacturers only include the information in the instruction manual. If your application is going to exceed the limits of your internal BEC, you’ll need to disconnect it and use an external model capable of meeting your needs. External BEC units generally provide far more capacity than internal units.
Most internal BECs can be disconnected by simply removing the red wire from the plug going to the receiver. Be sure to insulate it so it doesn’t short against anything. By removing the connector from the plug, you can reconnect it for another application.
Proper Wiring Methods
Castle Creations BECs are the only equipment I have on hand, but the same wiring precautions apply regardless of brand. Be sure to check your BEC’s maximum input voltage rating along with the output. The Castle BEC’s output voltage can be programmed to match your requirements.
The primary concern comes when using large packs in series to attain 10S or 12S motor power. The input wires to the BEC must be connected to “the most negative” side of the LiPo packs.
That can be confusing, but if you always ensure the negative wire from the BEC goes directly to the negative wire of the series connection (where the black wire from the ESC also connects) and the positive wire goes to that same pack’s positive side, you’ll be fine. This keeps the voltage within the range of the BEC and most importantly, prevents a dead short taking out an expensive ESC.
Carefully study the Castle Creations diagram and be sure you understand my explanation. This diagram depicts my Edge HV ESC, which doesn’t have an internal BEC, so it says not to disconnect the red wire. The diagram depicts the best way to wire an external BEC regardless of brand, but if your ESC has an internal BEC, be sure to disconnect the red wire.
If nothing else, remember that the black wire from the BEC and the black wire from the ESC should be connected where they meet the black wire from the first pack.
Benefits
The primary benefit is that you won’t burn anything up, and the secondary benefit is when you’re connecting the two packs in series to arm your system.
When the first pack is connected, the BEC will activate and provide power to your receiver. This will ensure the receiver is powered before the second battery is connected and the ESC arms. This is a nice safety advantage.
BEC Ratings
Regardless of a BEC’s manufacturer, check the ratings for output as related to input voltage. The higher the input voltage is, the lower the output capacity will be. Even if it’s listed at up to 12S or 20 amps, it doesn’t mean that is the BEC’s continuous rating.
You can have one or the other, but you can’t have both. This is another reason that connecting the BEC to one pack in the series is beneficial.
Never use two switching BEC units in parallel to power your radio system. If you need two to match the needs of your system, they must be separated from each other. Castle Creations is working on a possible resolution for this, but I don’t yet know of a marketed solution.
Glow/Gas Fliers ...
You can use an external BEC unit as an adjustable voltage regulator to power your Giant Scale radio systems using a LiPo pack as the source. If you have a large airplane using servos that won’t tolerate the voltage from a 2S LiPo pack, you can use a BEC unit to step it down to usable levels. It would be cheaper than replacing all of your servos with HV-rated ones.
I’m outta here! Hope to see you in Toledo!
