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Author Topic: Batteries and RX  (Read 2065 times)

BlueWotsit

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Batteries and RX
« on: July 24, 2010, 06:31:52 PM »

Recently bought a 6M class boat for non competitive sailing. As the access to the hull innards is via sealed sticky dacron patches at present I havent bothered examining the insides as I dont have any replacement sticky dacron.

All the electrics and RX are in a little pot accessible from the deck. There seems to be just the winch servo connection to the RX and the rudder servo connection to the RX - ie just the 2 connections to the RX unit.

Interestingly and the point of my question is that there is a PP3 connector to which I fitted a battery to see if it was external / additional power for the winch.

What I dont understand is why this battery is successfully powering the RX and hence the rudder servo as well.

A PP3 battery being 9v I believe, and I thought this would have been too much for the RX which I always thought would be powered by appx 6v.

I also tried the setup with an additional four pack of AA batteries connected to the RX.

I was happy to do these tests as I dont intend using the 27mhz receiver when sailing so if it had gone belly up I wouldnt have worried.

I dont understand why

(a) The PP3 battery on its own didnt blow the RX, yet still provided power for the winch and rudder servo

(b) Adding the 6v of AA batteries at the same time didnt cause a problem.

Anyone any ideas ? - could some form of BEC be fitted in line between the winch and the RX - but why didnt the direct 6v into the RX then have a problem


thanks
Andrew
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Shipmate60

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Re: Batteries and RX
« Reply #1 on: July 24, 2010, 07:56:49 PM »

Andrew,
Some of the 27 meg sets were designed for cars and did have an internal BEC fitted.

Bob
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BlueWotsit

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Re: Batteries and RX
« Reply #2 on: July 24, 2010, 08:33:28 PM »

thanks for that Bob, it was an old receiver, and the markings had worn away - didnt realise an internal bec might have been in something so old  :-))
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exvtop

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Re: Batteries and RX
« Reply #3 on: July 24, 2010, 10:52:26 PM »

Andrew,
I suspect the PP3 connector was connected to a 4 x AA battery box. I have one here with a PP3 connector on the end of the box.
Although you don't say (or know) what the winch is, I would think the reason you could connect a 9 volt battery to the system and not damage the receiver is that the winch is probably acting as a BEC like a speed controller would and is supplying the receiver with about 5 volts.
The Whirlwind winch on my One Metre works like this and I know Graupner winches do also.
The main danger would seem to be damaging the winch. As far as I know, most are designed for 7.2 volts max, i.e. a 6 cell rechargeable pack although such a pack would in fact be nearer 8 volts when fully charged.
Good luck with the yacht.
Mike
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Shipmate60

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Re: Batteries and RX
« Reply #4 on: July 24, 2010, 11:01:09 PM »

Andrew,
The old cars had resistor type speed controllers, but ran on 7.2 volts.
9 volts might be pushing it a bit!!

Bob
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BlueWotsit

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Re: Batteries and RX
« Reply #5 on: July 26, 2010, 08:44:38 AM »

mmm some interesting thoughts, looks like Im going to have to open her up and see what the winch is and go from there.

watch this space  :-))
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BlueWotsit

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Re: Batteries and RX
« Reply #6 on: July 26, 2010, 02:18:15 PM »

Well I opened her up and discovered a Whirlwind 7.2V sail winch - I think Im right in guessing this is quite a good quality one ??

Makes this an excellent value purchase perhaps .....

Now to logistics and I invite suggestions and comments

(1) I run everything on a 4 x AA battery setup - as this is the only size that will fit inside the circular pot that is fixed through the deck

(2) I install a 6 x AA battery or NiMh 7.2v setup inside the hull - downside here is I will spend a fortune on dacron everytime.

As I have no intention of competitive sailing, Im wondering about the viability of installing on the deck wooden hatchways instead of the dacron, so access is better

On my period sailing boats I of course always use hatches hence the consideration.

Over to you guys

cheers
Andrew
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exvtop

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Re: Batteries and RX
« Reply #7 on: July 26, 2010, 06:38:25 PM »

Andrew,
Believe the Whirlwind considered to be a pretty good winch although no longer being made.
Nearest currently available equivalent with turns adjustment seems be the Graupner Regatta or Futaba S5801 - both 100+.

Are you sure that five AA batteries in a 3x2 configuration won't fit in the pot? The pot on my One Metre is 6.3cm internal diameter by 8cm deep and five AA and a standard Futaba receiver fit easily. Four AA sounds a bit marginal.
If you do decide to fit a battery under deck it should be possible to bring a charge lead into the pot, sealing it's entry point.
A 2900maH pack should give you a few hours sailing without having to worry about replacing the battery.
Good luck,
Mike
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BlueWotsit

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Re: Batteries and RX
« Reply #8 on: July 26, 2010, 08:48:42 PM »

Hi Mike

I didnt realise you could get packs to fit 5 x AA batteries in, or did you mean a do-it-myself pack  %%

I think the pot is the same size as yours, it seems a standard size and has a branded MYA top to it

cheers
Andrew
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exvtop

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Re: Batteries and RX
« Reply #9 on: July 26, 2010, 09:24:49 PM »

Quote
I didnt realise you could get packs to fit 5 x AA batteries in, or did you mean a do-it-myself pack

Andrew,
No need to do it yourself.
See http://www.component-shop.co.uk/index.html
particularly http://www.component-shop.co.uk/html/body_5vp2600aa-m.html

Plenty of other suppliers I'm sure, but I've always had good service from them.

Hope this helps,
Mike
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BlueWotsit

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Re: Batteries and RX
« Reply #10 on: July 27, 2010, 09:46:15 AM »

Thanks Mike, I will give that a try 

cheers
Andrew
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BlueWotsit

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Re: Batteries and RX
« Reply #11 on: August 07, 2010, 09:51:47 AM »

Just revisiting this post as on dismantling a bit of the deck, I found one of those battery boxes but with a PP3 connection on the outside.

The unusual thing is that it is indeed for 5 x AA batteries as opposed to the more familiar 4.

I usually prefer to use Duracell type batteries as opposed to rechargeable in this format.

Key question is - duracell batteries usually equate to 1.5v each - so in this instance would be 7.5v total

 
Bearing in mind previous comments about fully charged batteries being near to 8v, will it be ok for the winch do you feel for me to run this configuration, seeing as how it is all stuck under the deck
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Mankster

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Re: Batteries and RX
« Reply #12 on: August 07, 2010, 10:34:18 AM »

No problem using 7.5v if your RX has a Bec fitted. If it hasn't a switch BEC is only a few theses days. I wouldn run a RX or Servos directly on 7.5v

BlueWotsit

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Re: Batteries and RX
« Reply #13 on: August 07, 2010, 10:37:07 AM »

thanks for that - the consensus of opinion previously was that a BEC must have been in the system somewhere
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