Technical, Techniques, Hints, and Tips > The "Black Arts!" ( Electrics & Electronics )

Reducing from 12v to 6v

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Doc:
Alan,
One solution is to use two 6 volt batteries.  Just one for the motor and both for the electronics.  Not exactly the 'best' idea especially if there's no room.  Swapping the motor for another one would seem like the simplest solution, maybe not the cheapest though.  Reducing the pitch of the prop instead of the diameter is probably the easiest/cheapest route.  But, like the old coot who runs this place, "What do I know?"...
 - 'Doc

AlanB:
Two 6v batteries looks promising.

The current, excuse the pun, battery is a 12v 7Ah, so replacing it with 2 x 6v 4ah is feasible.

As for removing the motor ? It is well stuck in the hull. The hull would probably give way before the motor.

Thanks for the help so far

malcolmfrary:
The simple, cheap, down & dirty way is to measure the resistance of the motor, and the get an old electric fire element and measure off enough to give about 2/3rds the value of the motor.  Using the screw type connectors, (solder doesn't work on that kind of wire) insert it into one of the motor leads.  Make sur that there is enough air space around it because it will get hotter the more you turn the wick up.  This makes a good, high-power resistor of the appropriate vale for your application, and it need not be too large, but as you have a 12v 7AH battery installed, I suspect that space should not be a problem.  If the performance drops too much, shorten the bit of element, if not enough, either put a longer bit in, or dont turn the wick up that far.  If the element starts to get too hot, use two or more in parrallel.
I did a home-made resistor controller many years ago using an old element from a dead toaster, and it was completely trouble-free.  The resistor elements lived in a separate compartment from the rest of the "works", which occasionally collected water when enthusiasm for sailing exceeded good sense, and this would give a bit of steam from the hatch, but it still worked for many years.
Rather than two 6volt batteries, a six for the motor and a 12 for the rest might be better - two sixes implies that the motor would be powered from the "centre tap", which works, but the two batteries will not discharge at the same rate, and this can lead to problems when remembering which is which when re-charging.

Malcolm Reade:
Hi Malcolm

The downside is the amount of energy lost by the battery in heating up your "resistor".  Shorter running times etc?

Regards, Malcolm Reade

johno 52-11:
Alan

Forget messing about with anything in the boat just restrict the movement of the lever on the transmitter. The advantage is that you will not be wasting any of the power in the battery and will have a longer running time.

John

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