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[loinerlad]

Hi folks,
I have just bought a small speed boat for my 12 year old nephew to take to the lake with me, The bloke I bought if off ran it on 6 duracell 1.2v 2450 mah rechargeable batteries which he said had seen better days and could do with replacing as they did not hold their charge much anymore.
The batteries he had were loose in the boat connected together with wires, I thought this looked a bit messy and the batteries just rolled around the boat so I have bought 2 battery holders each to hold 4 AA batteries which are now a lot tidier inside the hull.
I am just wanting to know if these will be ok as the boat is now running off 8 of the duracell batteries mentioned above, I have not had the boat on the water yet but it does seem very fast....maybe too fast for my nephew!! the motor is a Graupner 400, 4.8v

Any advice would be much appreciated
Thank you

[boatmadman]

Well, you are running a 4.8v motor on 9.6v, so whilst it may run fro a while, it will burn out sooner rather than later.

The other issue you need to be aware of is that having increased (doubled) the voltage you have also doubled the current, as shown by Ohms law, I=V/R, so you need to be sure the speed controller is man enough for the job, otherwise all the magic smoke will come out.

These guys: http://www.component-shop.co.uk/ are good for battery packs, and will make up a specific pack style for you if needed.

Ian

[loinerlad]

Oops, ok thanks Ian, do you reckon if I run on less batteries for now it would be ok as I have promised to take him to have a go with it tommorow?

[boatmadman]

Probably the easiest thing would be to run it on 6 batteries as it had been before you acquired it. Use the two battery holders, but modify the connections for 6 cells.

Ian

[loinerlad]

will do that! thanks pal.

[Tug-Kenny RIP]

 Seeing as you've got two new four pack's, why not wire them in parallel and have the motor running on 4 volts for twice as long.   

This will also make the boat run slower for your Nephew.   

Regards

ken
 

[Allnightin]

If you are still planning on 6 batteries, Maplins used to do a dummy AA battery that you could put in place of one or more of the normal ones until it goes at the speed you want.

[loinerlad]

Sorry Ken, this may sound really dumb but I am no expert and I am unsure what you mean by wiring them parallel  ?

Chris

[Tug-Kenny RIP]

On the blocks of four there will be the positive wire and the negative wire coming out.

You merely have to join the positives together and the negatives together and this will be your  5 volts supply at twice the amperage  (double run time)  that a single block of four batteries would have given.

This is called parallel wiring.  As you have it at the moment, it is series connected and all the batteries add together to give 10 volts if you've used 8 batteries.  This will be worst if the batteries are re-charged , because their value will rise above 1.2 volts each and then you've got smoke trouble and a short sail time. (if you get my drift )

regards

ken

[loinerlad]

Ahh, I see what you mean, that makes more sense to me now, I have nothing to loose so I am going to give this a go.

Thanks Ken 

[Tug-Kenny RIP]

My Pleasure.

Take your camera.      


ken

[loinerlad]

I wont be taking pictures of it with my camera if it goes up in smoke  although it would give everyone at the lake some entertainment!

[Tug-Kenny RIP]

Not us though.               


ken

ps

Rain forecast again.

[loinerlad]

Yes my nephew may well laugh but I have bought the boat and all the things it has needed so If it does I will just be watching my hard earned cash burning in the middle of the lake 

[hmsantrim]

 Hi Chris.
             your Graupner 400 motor operating voltage is 2.4-7.4v  with the nominal voltage being 4.8v  so at 7.2v its been run at the
             max voltage.  Ideally 6-7.2v would be the optimum battery voltage.  Dont know what space you have in the hull but is there
             room for a 6v sub c pack @5ah instaid of faffing about with loose cells and battery boxes. 
              Also is there no one in your area who could amp the motor to see if the s/con is up to the job instaid of all the guess work
              and bicycleclip attitude.

                           cheers Frank.
                           

[loinerlad]

I have taken this boat to the lake with my nephew this evening and it ran great on four batteries but we only got a short duration of use out of it as the batteries didn't last that long in the choppy water. I was thinking about a battery pack like the one you mentioned Frank, I am going to go to my local model shop with the boat this weekend and see if I can get one to fit in. Failing that it has 2 rear seats which I am considering removing and making this into a battery compartment.

Where theres a will theres a way 

[Stavros]

Go to the component shop website and read as it states the batt pack sizes in there,you will not find anywhere cheaper


http://www.component-shop.co.uk/


Dave

[malcolmfrary]

One thing to watch out for with more batteries on board - the boat will sit lower in the water.  Rather than a longer run time, maybe an extra pack and two runs?