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  Dock Power: Converting 220-volts to 110-volts

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Author Topic:   Dock Power: Converting 220-volts to 110-volts
dnh posted 11-08-2009 08:40 AM ET (US)   Profile for dnh   Send Email to dnh  
I have 220-volt power at the end of my dock for my boat lift where my 15 Sport is sitting. I do not have a regular outlet plug. I would like to charge the battery, but the charger runs on 110-volts.

I see some converters on the internet but do not know anything about electrical power and to not want to get shocked or cause a fire. Does anyone know anything about this stuff? Can anyone point me to a reliable, cheap converter?

Thank you.

jimh posted 11-08-2009 08:51 AM ET (US)     Profile for jimh  Send Email to jimh     
I know about this stuff.

If there is 230-Volt AC present, you may be able to wire a 115-Volt AC outlet to the circuit if the neutral conductor is provided. Otherwise, it would be cheaper to buy a 230-volt charger.

Alternating current can be changed in voltage by a transformer. You could also buy a 230-volt to 115-volt step-down transformer, but I suspect that would be an expensive solution. It would be cheaper to run a neutral conductor to the dock, it there isn't one already there.

These days many devices which provide DC power from an AC power source are rather liberal about the voltage of the AC power input, so you might be able to find a charger that can operate on both 115-VAC and 230-VAC without any particular modification. Some devices have a rather wide range of input voltages that they can work with. This would also be a good solution because the charger wouldn't have to be a 230-VAC only device. I don't know if your charger is built-in on the 15-footer or just something on shore you're going to temporarily connect.

jimh posted 11-08-2009 11:49 AM ET (US)     Profile for jimh  Send Email to jimh     
To give a ten-second primer on household AC wiring, there are usually four conductors involved. We call them:

G--or Ground. This conductor is at earth potential or zero volts. It is a safety conductor and should not carry any current in normal operation. It is meant to only carry current in case of a fault. Usually a bare copper wire or a green insulated wire.

N--or Neutral. This conductor is at earth potential or zero volts. It is a current carrying conductor. It is usually a wire with white insulation.

L1--or Line 1. This conductor is at 115-VAC above earth, It is a current carrying conductor. It is usually a wire with black, red, or blue insulation.

L2--or Line 2. This conductor is at 115-VAC above earth and in phase opposition to L1. It is a current carrying conductor. It is usually a wire with black, red, or blue insulation.

If one measure the voltages between the conductors, the results are as follows:

N to G: zero volts; N and G are bonded together at the point of primary power distribution in the system. Their voltage difference should never be more than a volt or so, which occurs when current flow on N causes some voltage drop in its distribtution.

L1 to N: 115-VAC

L2 to N: 115-VAC

L1 to L2: 230-VAC

From this you can see that a so-called 230-volt circuit is wired to L1 and L2, while a so-called 115-volt circuit is wired to L1 and N or to L2 and N.

In the situation we are discussing here, at the dock there must be conductors for L1 and L2. If there is a conductor for N, you can make a 115-Volt outlet by wiring it from N to either L1 or L2. However, it sometimes occurs that in a circuit dedicated to only 230-volt the N conductor is not run. If this is your situation, you would have to run a new line to the dock.

Inasmuch as you are not familiar with electrical wiring, and further concern exists because of the threat of a shock hazard around water, I would not recommend too much investigation into the wiring without the help of an electrician or a friend who is knowledgeable in this area.

Hoosier posted 11-09-2009 09:36 AM ET (US)     Profile for Hoosier  Send Email to Hoosier     
To add to Jim's tutorial, make sure that any outlet on the dock is GFI protected and that the plug housing is marine grade or specifically for exposed outdoor use, not just a box you'd mount on the outside of your house.

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