The Shipyard ( Dry Dock ): Builds & Questions > Any Other Builds

Speedo max current & motor combination

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justboatonic:
Can anyone give me an idea how I can ensure I buy the right amp rating speedo for my motor? I dont want to buy just any speedo and find it'll blow when I put power through it.

It isnt for a fast electric boat and I haven't yet decided which battery I'll be using. The motor is a typical 550, battery will be 6v 3.5amp gel or9.6v 3700mah NiMh cells.

Anyone got the formula to work out the max speedo rating?

boatmadman:
Hi,

Put a multimeter set for amps in line between the battery and motor and run the set up on a test jig with the prop in a tank of water. Then, to allow for safety, add 25% or so as a top current for running load. Then, add an inline fuse rated at the just below the max current rating of the ESC, that should protect it well enough.

good luck

Ian

boatmadman:
Hi,
Just another thought, if you use a higher voltage battery, the current pull will increase with the square(I think!) of the increase in voltage.

Ian

Fast Electricals:
If you can find out the stall current of the motor at the voltage you wish to use, buy a speedo that has a current rating at least 20% higher.

Neil

BobF:
Hi

If your use an Mtronics  (msonics) electronic speed controller, they automatically cut out if the max. amps are exceeded.
This is in addition to the advice you have already received.

Also they are completely waterproof.

Bob

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