Model Boat Mayhem

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: rickles23 on August 26, 2017, 11:27:17 am

Title: Sail winches
Post by: rickles23 on August 26, 2017, 11:27:17 am

Because of the original build I have to use two sail winches in a restoration.

The photo Sail Three is what I think I want.

Can someone check it?

The batteries I hope to use are 6V 3AH/20hr. Although I can change them.

Title: Re: Sail winches
Post by: malcolmfrary on August 26, 2017, 09:10:03 pm
The batteries quoted sound like rather nasty lead acid types.  I would seriously consider using NiMH 5 cell packs of similar capacity.
Will the two winches be working separately or together?  If together, a simple Y lead to plug the pair of them into, the object being to not have full current passing through the receiver. 
I've never really understood BEC receivers.  BECs, yes.  Working on the assumption that the makers don't either, I find it best to ignore such labels and make my own arrangements.  In sail3, the indication is that two batteries are connecting into a common power bus in the receiver.  This is not good practice.  The two batteries need to be treated as if they were BECs, and the red wires disconnected accordingly.
Title: Re: Sail winches
Post by: tigertiger on August 27, 2017, 03:21:31 am
I am running two sail servos + rudder + reciever on 6V using small AA battery packs and get a day or more sailing out of each charge.
Even if you have an auxiliary motor fitted, it won't get much use, and so a small battery pack should be sufficient.

I may be wrong, but I thought you only really needed a BEC if you need to protect components from higher voltages than they are rated for.  In most cases the transmitter, and most are 6 volt. With a 6 volt system, this should not be a problem.
Title: Re: Sail winches
Post by: malcolmfrary on August 27, 2017, 07:53:58 am
BEC receivers are supposed to withstand a higher voltage than normal, but presumably the internal BEC supplies a safe voltage to the internals of the receiver.   Whether this voltage is supplied to the items plugged into it is uncertain.  If it is, supplying a higher voltage to the controlled output pins as shown might not be good, unless the BEC has been specially arranged, it will not like having a higher voltage applied to its output, if not then OK, the regulated voltage just gets processed down to the RX circuit.
But, as per the drawing, if 2 batteries are connected in parallel, precautions need to be taken.  They do their best to even out their voltages by passing as much current as they can through the connecting wiring.  In theory, this might be too much for the battery.  In practice, the weakest bit will be the printed wiring in the RX connecting the pins and/or the connections to the pins, which will heat until either the batteries even out, or the weak bit melts, whichever comes first. 
The big trouble with lead acid, apart from the poor weight to energy stored ratio, is that they can deliver much more current than they can handle without damaging themselves.  The 3AH/20H quoted are capable of 150mA for 20 hours.  A sailwinch working will go well over that, so I would go for NiMH which is well capable of doing the job without damaging itself.  If each one is locally powered, then multi-ESC rules apply - disconnect red wires as appropriate.
Title: Re: Sail winches
Post by: rickles23 on August 27, 2017, 10:37:17 am
Hi and thank you for the replies.

I did plan to use the winches separately.

I will try a modified sketch a little later.