Switch or no switch?

[Chris FellowsParticipant @chrisfellows72943]

I'm just sorting out what needs to go where and the wiring layout for two of my Faireys. The River Cruiser is pretty straightforward as it has a single motor and prop shaft with a servo for the rudder. The Huntress LC is basically the same but having a stern-drive the motor is at the rear.

I've looked at the installation in DM's Huntress that he built and read his article again on electronics and have pretty much got my head around the installations. In his article Dave says that if you are in the habit of disconnecting the battery, which I am, then there is no need to fit a power switch.

I'm using HobbyWing Quicrun ESCs which have switches for the radio side of things so I'm not intending to fit a switch in the power cable. I'm a bit confused by Dave's Huntress though as he has fitted a switch (I'm guessing because the Hawk ESC doesn't have one) with very thin wires (red and black) to the thick red and black battery cables – the connections are hidden by heatshrink so I can't see what's going on. The thin cables only go to the battery cables and not to the ESC.

Anyway that's more of an aside. What are folks views on fitting a switch in the positive battery cable?

And I remember reading somewhere that you shouldn't extend particular cables but can't remember which ones and where I read it?

Chris

[Chris FellowsParticipant @chrisfellows72943]

[Dave Cooper 6Participant @davecooper6]

Hi Chris,

You could say that a switch is one more thing to go wrong. But, if it serves a useful purpose, then that may be a good reason to have one !

When you charge /change batteries what position would the switch be in ? Personally, I just disconnect my batteries (just in case) when charging using 'XT60' connectors.

I think there's a lot to be said for keeping things simple….

Cheers,

Dave

[Chris FellowsParticipant @chrisfellows72943]

Thanks Dave

Yes, you're right, keeping simple is good. In my yachts the batteries are left connected so their switches are useful, but in my power boats the batteries are left disconnected and they are taken out for charging so as DM said not really needed. I was just wondering what others did?

Chris

[Richard SimpsonParticipant @richardsimpson88330]

Hi Chris, I've always used a switch to turn the receiver off, usually one fitted to the ESC so everything is safe for when I turn the transmitter off, but I've never bothered with another one to isolate the battery.

When I take things out of the water I switch the radio receiver gear off, then the transmitter, then I disconnect the battery. Having said that I do have a model that has an inaccessible lead acid battery and I simply rely on turning off the radio gear and leave the battery connected. That battery is charged with a 3.5mm stereo jack in parallel with the terminals.

 

Edited By Richard Simpson on 11/04/2023 23:07:50

[Ray Wood 3Participant @raywood3]

Hi Chris,

I disconnect drive batteries of all types as I have a 20 mile drive on motorways to the lake and the idea of something smouldering in the back fills me with trepidation

You are getting worryingly close to having to put one of your boats in the water !! Well done

Regards Ray

[ashley needhamParticipant @ashleyneedham69188]

I simply fit and remove the batteries after sailing, have never fitted a switch for the purposes of disconnecting a battery.

Ashley

[Chris FellowsParticipant @chrisfellows72943]

Thanks chaps. That makes the installations simpler and less components to source and there isn't that much space in the smaller models to site and mount things.

Yes Ray, it is getting worrying close!!!

Any thoughts on what cables shouldn't be lengthened? I know it's Ok to lengthen the servo leads as you can get extensions and I will need to do that. 

Chris

Edited By Chris Fellows on 12/04/2023 10:40:30

[John W EParticipant @johnwe]

Hi there

Under normal practice I myself follow everybody else's advice and not fitting a switch into the main powerline of the supply batter. However, there is always one exception to the rule. This is when I built HMS Exeter.

I couldn't have cables connecting the 2 batteries together and so, I made a tray up. This is where the batteries sit on their sides and slide into the tray and on the bottom of the tray there are 2 brass tracks (negative and positive) and there are corresponding brass tracks fastened to the side of the batteries. If you are using this method you must ensure that you have the batteries the correct way around. From the brass contacts in the tray there are 2 heavy duty wires which go to an automotive toggle switch of 20 amp. Note the heavy amperage of the switch. This is to take the arcing that can occur when switching on and off across the terminals of the switch.

You know the words 'photographs are worth a thousand words' and here are a couple of photographs.

John

[Chris FellowsParticipant @chrisfellows72943]

Thanks John.

Only using one battery so I won't have that problem.

Been doing some searching and reading on Mayhem on extending cables. As is often the case there is some conflicting information but I don't think I will have a problem extending the cables as they won't be that long and I will be using good quality connecters and thick silicon insulated cable.

Chris

[ashley needhamParticipant @ashleyneedham69188]

I am sure I have read about extending cables, but can’t remember what was said. To my mind, for all practical purposes i don’t see what issue there would be extending any cables, other than an aerial one.

Losses incurred by extending power cables would be tiny, assuming you use the same gauge as the “end” items.

Interference may be the only gripe, but with 2.4 gig sets in use even that is a past consideration.

Ashley

[Colin BishopModerator @colinbishop34627]

Re switches, I usually fit them for the main battery and the RX which usually has a separate supply rather than a BEC.

I only build scale or near scale models and in most cases removing the superstructure means moving, removing or disconnecting various fittings and rigging such as davits etc. Doing this at the pondside is inviting trouble with breaking or bending things so I have switches, (and often charging points) concealed beneath deck fittings or hatches.

My idea of an ideal session is to check and test everything on the bench before I set out and don't open the model again until it is back on the bench afterwards. I usually make some provision for checking if water is taken on during sailing, either visually or by plumbing the bilges through a deck hatch with a syringe and tube..

My batteries are usually buried in the bowels of the boat and not amenable to being disconnected.

The only exceptions are my two SLEC Fairey powerboats which use LiPo btteries.and I store those in a fireproof box off the boat. In both cases the cabins just lift off the hull without obstruction.

Colin

Edited By Colin Bishop on 12/04/2023 16:46:38

[Tim CooperParticipant @timcooper90034]

Chris

I use the Quicrun Esc for my brushless motor models and use the switch on the Esc. I use switches on my brushed motor models.

Tim

[Richard SimpsonParticipant @richardsimpson88330]

Posted by Chris Fellows on 12/04/2023 11:58:00:

Been doing some searching and reading on Mayhem on extending cables. As is often the case there is some conflicting information but I don't think I will have a problem extending the cables as they won't be that long and I will be using good quality connecters and thick silicon insulated cable.

Conflicting information on Mayhem, you do surprise me Chris.

[Chris FellowsParticipant @chrisfellows72943]

Thanks for the further input.

Have done some more reading on RC Groups. Consensus is that leads between battery and ESC shouldn't be lengthened unless additional capacitors are fitted (I'm staying well clear of that!) as the ESC could be damaged due to increased inductance. Better to increase the length of the ESC to motor wires.

In the Huntress LC with the motor at the rear, I can actually fit the ESC so that, surprisingly I don't need to extend either but as it's under the cockpit it would have to sit on the hull bottom and alongside the battery which I'm not keen on.

So I'm about to look at siting it in the cabin with probably a shelf over the snakes/servo.

Chris

[Ray Wood 3Participant @raywood3]

Hi Chris,

The need to do anything fancy with the leads from the battery if you extend them to the ESC sounds like mumbo Jumbo to me, some of the technical advice on forums is from boffins who know the theory but no practical experience ?

As they say ignorance is bliss in my case, I have never had a problem, lets face it the ESC may never have read the book

Regards Ray

[Colin BishopModerator @colinbishop34627]

I have to agree with Ray, I can't imagine how extending power leads in the confines of a model boat hull could remotely have any practical effect.

Colin

[Chris FellowsParticipant @chrisfellows72943]

Yeah, I was reading it with my cynical hat on but some of it does seem to make sense and one of the manufacturers (Castle) concurred with it being Ok to extend the ESC to motor cables. Some folks don't experience any problems and others have. But some examples were quite long runs in aircraft and others were using very high voltage batteries so not the sort of scenarios we normally encounter in our type and size of models.

For most of our builds as well, the battery, ESC and motor(s) are usually pretty close together and so the issue doesn't come up and if cables do need to be extended it's usually not by that much. The question only arose with me because of the motor being right at the rear and the restriction of having a low cockpit floor making it difficult to site the ESC. Always good to do a bit of research though and add to the knowledge base.

Anyway, shelf now constructed so that the ESC can go in the cabin area. Just need to order some gold bullet connecters to extend the motor cables and finish the installation.

Chris

Edited By Chris Fellows on 13/04/2023 23:52:37

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