Bec, ubec, rx pack ???

[Simon.O.]

As usual I have been up and down the forum and am very used to using the search function. It can be a very informative as you read about all sorts of stuff that you normally wouldn’t look for. A bit like you-tube really.

Anyway todays topic is Rx, Receiver power.
This is for my 6-cell brushed fleet.

Both of my most used ESC’s have bec output.
I have not yet trialed my new rx on bec only, I have run it very happily with a 4 x drycell pack.
I have been advised that it is better to run a separate rx pack in any case.
To go Nimh means a 5 cell pack, correct ??
What is the minimum mAh I can get away with. I can do a really small and light pack at 350mAh. Or be a little more conservative and take the weight with a 600mAh.

External bec or UBEC.
This naturally bypasses the esc and I understand is usually used if an esc does not have bec output. Am I right in guessing that as this still uses the main power that I will be no better off than using the esc bec output, or have I missed something here.

My options
4.8v rx pack
6.0v rx pack
350mAh or 600mAh
UBEC
Run the rx off the esc and stop thinking so much.

[ED66677]

To go Nimh means a 5 cell pack, correct ??

yes but 4 works as well, just slower servo's

This naturally bypasses the esc and I understand is usually used if an esc does not have bec output

yes

Am I right in guessing that as this still uses the main power that I will be no better off than using the esc bec output, or have I missed something here

except if above a certain cell count the ESC's BEC has to be disabled

My options
4.8v rx pack

additionnal weight

6.0v rx pack

additionnal weight

350mAh or 600mAh

350 sounds very small to me

UBEC

good idea

Run the rx off the esc and stop thinking so much

yes if you can

Another option would be a small and light weight 7.4V Lipo pack with UBEC, no power taken from propulsion pack (few extra milliamps for extra run time, and possibility to choose 5 or 6V output on the UBEC, 5V might be necessary in case of use of certain digital servos!

[azjc]

there has been a raah of the CC BECs failing and when they do they allow all of the current to pass and this can fry your Rx and servo's, I am not sure about other brands though, I use the Western Robotics Hurcles HV BEC and have gotten great results

[Mich. Maniac]

I use Novak HV bec in all my boats. even the sv. its just added protection incase esc failure and no added weight. Only drawback is 30.00. I then tap into esc power leads about halfway and have had no trouble.

[Simon.O.]

All is now sorted.
I use a 9v flat cel that is common in domestic smoke detectors, I hope you all have one !!
I have no bec output on my new BL esc so an alternate power supply was found.
This single brand name cell has now had a lot of runs and shows little sign of power loss.
I recently did some bench testing and drew up a data sheet of current draw for a Rx, loaded servo and an esc (working) and found that the 150mAh from a 9V square cell is plenty enough for my small FE hulls.

It is small light and easy to fit in all of my hulls so for me a 9V square cells is it for Rx power.

[Flying Scotsman]

Simon, just a word of caution. 9V may be too much voltage for some brands of servos.

Douggie

[n.h.schmidt]

9v radio batterys

Hi Simon
It may not sit well with some of the guys but I have used the little 9V batteries in many of my boats . Only the alkaline batteries will work for this. If you tried to use heavy duty or standard ,you wouldn't get ten laps out of it. A alkaline may last all summer if you remember to turn off the receiver after every run.
It is also true that the higher voltage may not work with every receiver type.
n.h.schmidt