Hi Guys,

given the appalling weather whenever I was available to go to the field in my attempts to learn how to fly this year I have made very little progress so I thought that I might try to do some indoor stuff over the winter… So having asked around, done some research etc I finally made a purchase of a ‘foamy’ and all of the attendant gubbins I needed to get it into the air.

Building the thing is no problem; snip, cut, glue, pin, trim, swear etc in all of the right proportions as dictated by the instructions, or lack of them. My problem arises in wiring the electrics. Obviously, the servo to receiver connections are straight forward, as are motor to ESC and ESC to receiver (‘Thro’ socket). My problem, and hence my question, lies with the battery.

The battery is a very slim 400mAh 3S 20C 11.1v LiPo with only two bare wires and no balance lead. My ESC, as previously mentioned, has easily identifiable motor and receiver connectors plus two bare wires (sounds like a battery feed to me).

Since this is an electric airplane I am presuming that I need to power both the receiver and the motor. Is it just a matter of using a ‘Y’ connector to couple up to both the bare ESC wires and the ‘Batt’ socket on my receiver or am I missing something vital?

Thanks in anticipation…..

The two battery leads connect to the two leads on the ESC make sure you get them round the right way

• red to red
•  black to black.

I am unsure as to which cabling you are referring to. The 2 x main power leads from the ESC should be readily identifiable and either coloured red /black ( or maybe blue ) and obviously conect ( via suitable plug/socket ) to the flight battery.

If these are not coloured, then there will likely be a marking on the ESC itself ( it may be a bit hidden ) showing +/-

The ESC will also likely ( as Bruce says ) have a BEC lead coming off it. This looks like a servo lead, and plugs into the throttle channel, supplying power to the radio and allowing throttle position commands to be fed from the Rx to the ESC.

I dont like the sound of "2 x bare wires" coming from the LiPo !

Please post a picture  - do NOT connect anything up until we are sure we know  what is happening here.

Thanks chaps, I've fallen into the trap again of assuming you can make sense of my inadequate descriptions... DOH!

Indeed the 'bare' wires are colour coded black and red. I guess I was trying to imply 'bare' = 'wires without fitted connectors' rather than 'wires stripped of insulation'. The ones on the battery are also insulated with heatshrink so there is no immediate danger of shorting. I will only be uncovering them one at a time for connection purposes and recovering/insulating each before I move on to the next step.

I had lost sight of the BEC aspect of ESCs so your reminders are both welcome and make me feel a bit dumb. I had looked through several pages of posts on the subject but nothing had triggered my personal "Doh, that's it" circuitry. Additionally, there was nothing mentioning BEC connectors on the comprehensive instruction sheet which came with the ESC. I guess the manufacturers assume a basic level of knowledge  which I appear to have slipped under... Old age, don't ya know... well that's my excuse for the moment...

Fortunately, I am of the "measure twice, cut once" school of engineering so there was no chance of me connecting a LiPo without seeking advice or knowing what I was doing.

Here's the equipment in question

I am proposing to use a couple of 'mini' deans type connectors with the negative from the battery connected to the protruding pin as layed out in the picture. Do you think that I would be better off using full sized Deans connectors, of which I have a supply, with the protruding pins coming from the ESC, as per standard battery practice, given that we are talking LiPo's here?  I think that I have probably just answered my own question as the weight saving aspect is more than outweighed by the safety considerations.

Bruce, Timbo and Eric....  as always, thanks for the informative replies and being there to assist us all when we cry for help. The greatest danger is when we don't know that we need help and don't cry out!

Just in the process of setting up my first electric model and I have one additional question relating to the installation. On IC's we use a receiver switch! does this not apply when using electric setups?  

When I used to run an electric racing cars we all fitted on/off switches. Is there a reason why electric planes/helicopters do not have one fitted? It would seem to make sense from a safety point of view, given that the machine is 'hot' while you are fiddling around with wings/covers/canopies etc in fairly close proximity to a prop or rotor which can easily be set in motion by a very small inadvertant movement of the stick (or someone else's transmitter if frequency control is ignored/compromised). Am I missing something (again) here ?

Timbo maybe you could do a sticky in the electric or newbie section on the BEC questions as it seems to pop up a lot ref how it all connects together.

Hi Ralph, thanks for labelling the picture, hopefully it will be useful to others if Tim can make a sticky incorporating it. I really should have used a better background rather than my grungy bench with a soiled mat on it....

I'm assuming that an on/off switch, if fitted, should live between the ESC and the Receiver to inhibit the passage of signals to any of the equipment. Of course this would still leave the possibility of a signal being passed in the event of an ESC malfunction. Am I right in assuming that if it was fitted between the Battery and the ESC there is the likelihood of getting too much current through it when the motor is working hard ?

I prefer the ESCs which do NOT have an isolating switch fitted!

IMO the ONLY sure way of isolating the power to the motor is by physically unplugging one or both of the main battery leads. A switch or other isolator in the main leads is only practical in heavy large models, as this device needs to be able to handle a very high current, and therefore by its very nature will be large and bulky - I know some people have successfully incorporated a DEANS plug /socket mounted in the fuselage and used as a bridge.