Getting ready to switch a couple of gas planes to electric, Power 46...4s4000, the question is, If I use a onboard reciever battery and get a non-bec ESC, Will that work or do I also need one of the addon Ubec units.

You will likely get some better answers than mine but I do think you must have a bec or Rx will go boom, too much voltage.

Using a receiver battery will work fine with a non BEC ESC.

I would get an esc with a switching bec such as a castle creations. It's a lighter set up, and you can change the voltage going to the reciever/servos.

All of the above, I think . If its a receiver battery, that is one whose voltage does not exceed your receiver's, than yes you can. As you may know the idea behind the BEC (Battery Eliminator Circuit) was to remove the weight of the receiver battery. If you have a large aircraft that doesn't care, the incentive is all your main battery energy goes to powerplant, but usually the servos and receiver draw so little it doesn't seem to be worth it. Some would still run a receiver battery through a regulator...

Why a regulator if the receiver battery is the proper type and voltage? A 600 mah NiCd or NiMh 4.8 volt pack does not need a regulator.

CGr.

Ok..I forgot to mention that i am planning to use a 4.8 volt receiver battery, i have 600 or 1100.. And the only reason i even considered and non-bec was cost, and maybe a added safety value in having the main control servos on a 6-8lb plane on a reciever battery vs. bec circuit .

Good question, CG, not really sure why... Not sure if it was a hold-over from a previous setup or if they thought it would some how provide more consistent voltage... It was on a big electric heli.

Ok. Well, consider this: Electric flight is already somewhat complex as compared to glow. You have at least 3 controls (Rudder, Elevator, Throttle) and in some cases four (Aileron). Add a receiver, an ESC, an electric motor, the battery pack, and you have the barest minimum setup for electric flight. This is a conversion. The OP said "Gas to Electric" but then said "40 size" so we are talking glow, not gas. Just a minor point, but I just wanted to clear that up.

Anyway, in this case, since we're talking about a 40 size conversion to electric, I will assume a fourth servo for the aileron. These servos are not micro servos, they are at least standard service servos, similar to an Airtronics 94102Z or Futaba S3003, both are standard, bushing type servos. As for the Futaba, the manufacturer recommends the following:

I will assume the same is true for the Airtronics, or Hitec, or any other servo in that class.

For this very reason, I would recommend a separate battery with an ESC without BEC (not necessary so why pay extra for it). The OP stated he has a 600mah and an 1100 mah 4.8 v receiver battery. This is the way I would definitely go. Forget the LiPo and regulator for the receiver... redundant, ie. unnecessary, and adds unnecessary complexity. It, the LiPo, is needed for the ESC and motor.

Make your weight measurements (see below) separately, once with the 600 mah and once with the 1100 mah. I would go with the 1100mah, but I am the type that likes the warm-fuzzy with having just a bit more available.

Be sure to do the math to insure that the motor/esc/LiPo pack are sufficient for the weight of that airframe it is going in. Weigh it with everything intended for flight, or if the motor/esc/battery pack have not yet been purchased, use the numbers provided by the manufacturer, weigh the airframe, add the weight of the p ower plant, then do the math to see if the power is sufficient. If not, well, move up to a higher power and re-do the math. At some point, you will find the right combination for safe flight.

Make sure to include the receiver battery in the equation.

Use this guideline in selecting the proper power for that conversion:

Basic algegra.. [X(] : you have 11.1 volts (nominal) for a 3 cell Lipo, say 110 watts per pound for sport flying, say 7 pounds = 770 watts. The math says that you will have a current draw of 69.4 amps.

So, this conversion will need a sufficient battery for 70 amps maximum draw and a motor that will give you the right power, 770 watts.

CGr.

I just asked about the regulator on a receiver pack on another forum and one of the answers was that the owner may have been using a LiPo pack of higher voltage (like a 2S) because he wanted to use some small LiPo batteries he had on hand and not have to use yet another battery pack.

Love the motor selstion gouge above, CG, its a keeper.

I've made a couple of edits, so re-read the post to get it all.

I understand where the regulator discussion comes in.. it comes up all the time. For basic flight, and for most of the level of RC in this forum (it is a beginners forum.. ), a regulator just isn't necessary.

CGr.

If using spectrum, I would still use a 6.0v reciever battery just because of brown out issues.

The "brownout issues" have been fixed. They (Spektrum) took care of that several years ago. But, not withstanding, I'd go with 6 volt packs for the extra torque and speed that the servos provide with 6 volts.

CGr.

Thanks guys, that cleared up a lot questions, I do use Spektrum on all my planes so will go with the 6v battery, for torque and be on the safe side.

CGR ..I will use your chart to figure out final choice of motor , ESC and battery combo. The one plane is a FW190 57" ws and had a os 40 in it. The other is 80" cub new build, so no prior setup, both should be 6-7 lb range.

This is the tenitive setup. Was planning on using for both. They have different KV rated Power 46 so input welcome.


The G46 (50-55-700) Power 46 brushless out-runner motor can replace a .46-.55 two stroke nitro engines.
It is equivalent to AXI 4120 and E-Flite Power 46. It is capable of producing up
to 9 lb of thrust and generate about 1000W of power.

Specifications:

* KV: Listed as 700, tested to be approx. 730.
* Weight: 10.6oz (300g) for motor only, not including mounting accessories.
* Motor Diameter: Approx. 50mm
* Shaft diameter: 8mm
* Max efficiency: Approx. 50A
* Max Load: Approx. 60A

Motor Dimensions:

Recommended Setup:

* 80A Opto brushless motor ESC
* 3-5S LiPO and at least 4000-5000mAh.
* Prop Selection: Remember to always use props designed for electric motors, nitro props are heavier and might overload the motor.
With 5S LiPO: 12x6, 11x5.5
With 4S LiPO: 14x6, 13x6.5
With 3S LiPO: 14x8, 13x8


Hobbywing Pentium 80A Brushless ESC

1.1 Output: Continuous 80A, Burst 100A up to 10 Secs.
1.2 Input Voltage: 2-6 cells lithium battery or 5-18 cells NiCd/NIMh battery.
1.3 BEC: None.
1.4 Max Speed: 210,000rpm for 2 Poles BLM, 70,000rpm for 6 poles BLM, 35,000rpm for 12 poles BLM.
(BLM: BrushLess Motor)
1.5 Size: 70mm (L) * 31mm (W) * 14mm (H).
1.6 Weight: 58g.


Think I will upgrade the battery

GForce 30C 5000mAh 4S 14.8V Lipo

Description

* 5000mAh Capacity
* 4S - 14.8 Volts - 30C Discharge
* 146mm X 50mm X 33mm (5.75in X 1.97in X 1.3in)
* 540 grams (19.5oz)
* Comes standard with Align/E-Flite balancing taps (JST-XH)
* Deans connector installed

Well, it certainly looks like you did your homework. Best of luck with the conversion. Let us know how everything works out.

CGr.