Electrical Power and Cable Size

[grahamoParticipant @grahamo]

First post so please be gentle with me! Hope I’m not asking a regular question, but couldn’t see a search option.

 

I’m building a model boat, about 90cm long which will be autonomously controlled and I’m slowly getting round to the power installation side of it. However the one thing I can’t find is what size cable I need for power connections from the battery to ESC and then to the motor. It isn’t a performance craft and endurance is more desirable than top speed, so it isn’t going to be taking 10’s of Amps. Battery is 7.2V LiPo and the motor is a 500 size, which I hope means something.

My “local” model shop has this wire in stock, (G-Force Silicone Wire Powerflex PRO+ Black 20AWG 255/0.05 Strands 1m) but I’ve not been able to find a current rating for it .

Any help would be much appreciated.

Thanks

Graham

[David Marks 2Participant @davidmarks2]

Graham

Most of us use an extremely good supplier called Componentshop. Find their website and view their catalogue and on Pg. 48 you will find the information that you are looking for. I have only got an interest in electronics to support my interest in building model boats, but when I want that type of information, that is where I get it from. Also somewhere on the MB website there should be an article by the late Dave Milbourne entitled (I think) “But i don’t understand electronics”. Dave always wrote in plain English, very factual and straight to the point.

[Colin BishopModerator @colinbishop34627]

I agree with David, Component Shop Website shows various sizes of silicon cable, this page shows that 20AWG can carry 11 amps continuously. You can check the specifications for the otther sizes. Silicon cable is good to work with as it is very flexible.

https://www.componentshop.co.uk/20awg-silicone-cable-wire.html

The article David mentions is not properly available on this new website yet as there is still conversion work to be done on the photos but you can read the text here:

But I don’t understand Electronics!

Colin

 

[Len Morris 2Participant @lenmorris2]

Hi Graham,

Well come to the forums and well done for building such a large model.  I wouldn’t worry about electric wire size unless you’re into serious fast electrics, water cooled motors etc.

If you do all the sums and calculations for the correct size, you will come up with a surprisingly small value.  Unless you need to use fine wire because of installation restrictions or cosmetics, just use the wire you can buy from car shops for wiring accessories.  I think you will find it much cheaper than specialist model shops, easy to use, and well on top of the job.  Good Luck.

Len

[grahamoParticipant @grahamo]

Thank you all for your help. The last model boat I built was about 48 years ago, so things have changed a lot to put it mildly. I’m not building this model as a representation of anything, but as an platform for experimentation with the electronics. I’ve built the RC gear and am currently trying to get the GPS calculations to work! The final model will hopefully be able to follow a set of preprogrammed waypoints for 24hrs or so.
Unfortunately there aren’t many model suppliers, or not that I’ve found so far, here in Portugal, but most things are available. I’ll be back in the UK in January so can smuggle stuff for the boat back then, as well as more Marmite!

The model I’m building is just a simple set of plans from the web and Youtube, which I have modified and really enjoyed building the hull, even down to balsa planking to get flared bows and although the finish isn’t great, it has got me hooked on building something else when this project is finished. Currently the hull is finished and watertight, but now it is time to fit the motor and propeller shaft and then make decisions from there. I will post some photos as the project progresses.

 

Graham

[Colin BishopModerator @colinbishop34627]

I didn’t realise you were in Portugal. Component Shop will ship to you but, as Len says, the wire used for wiring car accessories would be adequate for your purposes.

Sounds like an interesting project so, yes please, post some photos and more information in due course.

Colin

[Richard SimpsonParticipant @richardsimpson88330]

Its also worth remembering here the advantages and disadvantages of silicone sheathed cable over PVC or any of the other hard sheathed cables.  The silicone is obviously so much more flexible it can make laying it in difficult runs a lot easier in a model boat.  Keeping the wiring tidy can then be a fairly simple exercise using self adhesive cable tie pads etc.  If however you are wiring up some sort of distribution board, say for lighting, you might find that a hard sheathing is easier to lay in nice straight runs with right angle bends.  A lot of it is personal preference.

The number of strands is also well worth bearing in mind.  For a given cross sectional area, csa, the more strands the more flexible the cable is.  Sometimes you might want flexibility, sometimes you might want rigidity.  A lot of it is just personal preferences.

One thing guaranteed to use up my patience pretty quickly is cheap wire with cheap plastic sheathing that seems to have a mind of its own.  It neither stays where you lay it nor is is flexible enough to follow a complex run. As I am a huge believer in a neat and tidy electrical installation, it helps keep you focused on the installation, it is so much easier to trace a fault in the future or make modifications and, let’s face it, the internals look so much better, I always avoid cheap cable!

 

[grahamoParticipant @grahamo]

Richard, I agree that wiring can make or break a project when it comes to maintenance. With my electronics projects I have tried many types of wire from “that’ll do quality” to something which comes at a premium price. If it doesn’t move, then rigid wire is best, but short lengths of flexible wire are a necessary evil sometimes.

Thanks for your input.

 

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