Battery size to power a 9g single servo

[Peter Brown 15Participant @peterbrown15]

In the process of building a small Aeronaut Clipper Yacht. What size NiMH battery would I need to power the ESC, receiver and a single servo for the rudder.

[Peter Brown 15Participant @peterbrown15]

Clipper Yacht

[Dave MilbournParticipant @davemilbourn48782]

Peter

Rather begs the question why you need an electronic speed controller in a small yacht. If it's because the yacht has an auxiliary motor then the battery will also presumably be driving that. Much the same goes for a motorised winch. Goalposts are moved at that stage.
We need a little more information, please.

Dave M

[Peter Brown 15Participant @peterbrown15]

Dave, all I need is a set up to operate the rudder and that’s all. No winches as fixed sail. Basically what do I need to operate the servo in the way of power.

[Dave MilbournParticipant @davemilbourn48782]

Peter

A receiver and one 9g servo won't draw much current at all. The simplest advice would be to ballast the model down to the required waterline, then weigh the ballast and buy the largest battery pack which is under this weight and will physically fit into the model. Component Shop give the dimensions and weights of all their NiMH packs – you're after a 4-cell (4.8v) pack. **LINK**

Dave M

[Malcolm FraryParticipant @malcolmfrary95515]

A pack of 4 AAA cells will do the job nicely. Works very well in the DF65 yachts, and they have a winch as well. No ESC needed, just battery, radio, servo, thats the lot, maybe a switch that can carry the current in the harness. Alternatives are 5 AAA for a bit more thrutch on the servo but at the risk of overloading it, or 4 AA, for much longer run times t the cost of more weight.

Since batteries need recharging, usually out of the boat, the simplest idea is battery – extension lead plugged into the radio – servo plugged into the radio. That saves messing about plugging the battery into the radio at the start of a session, just plug into the end of the flying lead.

Dave is well used to powered launches where his payload idea works well, but a windy boat needs to have as little weight about it as possible apart from the ballast weight, which needs to be as much as possible while still floating "right".

[Dave MilbournParticipant @davemilbourn48782]

Hang on, Malc – isn't that what I said (or is your 'ballast weight' that bulb thingy on the end of the keel?). I'll happily admit to knowing the square root of Fanny Adams about rag-and-stick models.

DM

[Peter Brown 15Participant @peterbrown15]

Am I right in thinking the battery connects directly to the receiver.

[ashley needhamParticipant @ashleyneedham69188]

Yes. The receiver will have a battery port on it besides the 1-6 channels (or how ever many are on it)

​If you have a ballasted keel, then the battery could do with being less heavy than Dave`s idea which he is touting as using a big battery to provide all/most of the ballast weight to benefit run time.

​Both ideas are sound but it depends on the style of boat that you have…

​Ashley.

Edited By ashley needham on 16/03/2018 17:51:40

[Peter Brown 15Participant @peterbrown15]

The keel is ballasted with a steel torpedo. I’m thinking of a 4.8v mini battery as there isn’t a lot of space.

[Malcolm FraryParticipant @malcolmfrary95515]

Posted by Dave Milbourn on 16/03/2018 11:46:07:

Hang on, Malc – isn't that what I said (or is your 'ballast weight' that bulb thingy on the end of the keel?). I'll happily admit to knowing the square root of Fanny Adams about rag-and-stick models.

DM

On a windy boat, the thing that keeps it upright and lets the sails make it go is the shapely lump at the bottom of the fin. Ideally, t should be more than 50% of the total weight, but within the limits of having the boat float at a sensible waterline and not break the fin, as much as possible. This means that the hull and masts and anything that goes inside the hull needs to be as light as possible while being strong enough to do the job. So not a large battery, there is not the payload for one.

Dave, its maybe about time you persuaded somebody to let you have a go with a rag and stick boat. Its a whole different world, and there is plenty of enjoyment to be had taking one for a walk, it isn't just racing.

On https://www.componentshop.co.uk/batteries/radio-control/receiver.html there is a selection of 4AAA packs, any of which will do the OPs job.

[Dave MilbournParticipant @davemilbourn48782]

Dave, its maybe about time you persuaded somebody to let you have a go with a rag and stick boat. Its a whole different world, and there is plenty of enjoyment to be had taking one for a walk, it isn't just racing.

I did once bite the bullet and bought a Graupner Micro Magic kit from Martin Davis and a Hitec radio to go in it. It sat under my bench for two years until it was decided that we were moving house, so I let Ray Wood have the kit and Vincent Poncia had the radio along with the original Huntsman. Maybe one day, but I have the small matter of a new workshop to build first. BTW your treatise on ballast in model yachts makes perfect sense to me.

DM

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