to b.e.c. or not to b.e.c. ??

[forescott]

I recently purchased an Ammo 36-88-1280kv brushless motor, xl water jacket, 2-5000mah 3s 35c turnigy lipos, and a turnigy 120A speed control that I want to put in a 31-inch mono. All of my other setups in my boats are 4s and this will be my first 6s setup. I have heard of others unplugging the red wire from the esc and using an rx pack instead of the bec. Why is this done?, and is it necessary?? Is this normally done on higher voltage setups? I want to do the right thing!

[Alfa Spirit]

With high voltage like 6S/22,2V use an Rx pack or external UBEC. ESC' s BEC are light and many of them burn.
An UBEC isn' t expensive, I' m looking to Hobbywing UBEC-3A (2-6S Lipo Input)

http://www.hobbywing.com/english/ArticleShow.asp?ArticleID=454

[crabstick]

I personally use an RX pack.. A small 800mah 2s pack for the little boats with a UBEC
For gas I use a larger battery mah 2s with UBEC

[forescott]

With high voltage like 6S/22,2V use an Rx pack or external UBEC. ESC' s BEC are light and many of them burn.
An UBEC isn' t expensive, I' m looking to Hobbywing UBEC-3A (2-6S Lipo Input)

http://www.hobbywing.com/english/Art...?ArticleID=454

So a "ubec" goes in-line between your speed control and your receiver? And it basically regulates the voltage coming from your speed control as not to fry your receiver?

So is the built in bec on the turnigy 120 not a reliable way to power the receiver when running on 6s?

[forescott]

I personally use an RX pack.. A small 800mah 2s pack for the little boats with a UBEC
For gas I use a larger battery mah 2s with UBEC

A 2s pack is 7.4volts right? is that the correct voltage to power a receiver/steering servo?

[blackcat26]

From what I understand it gets sketchy at 6s.....Might work, might not. It is taking a small amount of power away from your motor by using the BEC and might be adding a little more heat from what I have read. I used a battery pack on my twin. One less thing to worry about in my book!

[tiqueman]

I use this http://www.offshoreelectrics.com/pro...portbec&cat=72

A lot lighter than a battery, smaller and worth it not to blow an ESCs bec running on 6S.

[Alfa Spirit]

No, the UBEC give a DC 5V or 6V from batteries

[crabstick]

yeah the UBEC sits between the RX and RX pack and drops 7.4 to 6v in my case.

only thing I use BEC in is my BL planes and Heli. My n2 speedie doesnt have bec so i run a rx pack in that too.

[vasy]

The real question is, if BEC inside the ESC is linear or switching type.
If it is linear, max is about 4s with 1 strong servo to be on the safe side. If it is switching then on 6s you can run 1 servo no problem as it does not generate much more heat than on 3s.
As per seaking website the BEC is switching type, so no problem running 1 servos on 6s. It will produce maybe 4 to 5 extra watts of heat but not enough to make any difference one way or the other.
Good luck with the read if you want math behind the difference: http://www.rcuniverse.com/forum/m_7683693/tm.htm

[Jeff Wohlt]

Best on the ESC to not use them at all. UBEC or a pack.

[forescott]

Thanks to all for your input! I will research the turnigy 120 to gat a little more info on the bec's capabilities. If I decide not to use it I'll probably go with the ubec that steven sells.

[Jeff Wohlt]

Smart move...it is the ripples that hurt a BEC when internal and it makes the ESC work harder.

[vasy]

Smart move...it is the ripples that hurt a BEC when internal and it makes the ESC work harder.

I take it you never took apart an good ESC to make a remark like this.
Every good ESC I took apart has a BEC on its own board or circuit, no I don't claim to have taken them all apart, so "spikes" in power have no affect on the BEC as they have no relation to one another. It is the same if adding a BEC on its own just placing it inside the neat package of the ESC. The extra heat produced is negligible compare to the ESC under load.
I've run several quality ESC under full 6cell load with build-in switching ESC at 80 to 100 amps with 4 - 5 servos and no failures, maybe I'm lucky?

at the end you should go with what you feel best for yourself.

[Meniscus]

When I first started back up in this hobby, I really liked the convenience and not having to worry about a battery pack or the extra weight.

For the last year or so, I switched over to running a standard battery pack, specifically 4 AA's. No, it's not convenient, but I haven't had a single issue since I switched over. I spend a little extra money on Energizer lithiums. This keeps the weight down and the power doesn't dip when running a higher demand load such as a high torque servo, etc.

So, if you decide that you'd like to run an extra battery, I don't think you'll be disappointed.