I live on a US sailboat right now off the coast of New Zealand. My Mac will only recognize power input from a land-based source. It will not charge from either a 110 or 220 outlet on the boat. Any suggestions?

Use what works.

The standard power brick is rated 100-240VAC, 50-60 Hz. Maybe the power supply on the boat falls outside that range of voltage/frequency or the power waveform is not a pure sine wave. Perusing the power section in the Apple Store, I can envision two alternatives:

If you can get 12VDC with sufficent amperage off the boat's electrical system, you could get a DC to AC power inverter such as this and use that with your standard power brick:

http://store.apple.com/us/product/TW696LL/A?fnode=MTY1NDEwMQ

If you can get 15VDC with sufficent amperage, you can try and jury-rig the airplane adapter and use that instead. Beware, it MUST be exactly 15VDC; if less, it won't work, if more, you'll fry the Mac:

http://store.apple.com/us/product/MB441Z/A?fnode=MTY1NDEwMQ

Costs some money, but I would ask local electricians to create a converter box, based on the VAC/Hz ratings and knowledge of marine electrical supply specifications.

Unless all of the local New Zeland electiricans and marine service electricians have declined already ...

My humble opinion.

Might want to try something like a battery backup. We use these at work.

http://www.apc.com/products/category.cfm?id=13

Boats usually have 12V DC outlets as well, like cars. You might want to do away with the (wasteful) conversion from DC to AC to DC, and just use the 12V outlet to power/charge your Macbook:

http://mikegyver.com/IdeasnProducts/MikegyverKit/

Quote from the page:

You can charge your Macbook / Macbook Pro / Macbook Air on the Airplane, Car, Truck, Boat and house! NO more wasted energy using inverters!

If that doesn't work, they also have a fat battery which will definitely work:

http://mikegyver.com/IdeasnProducts/PP130-Macbook-External-Battery/

One of the big problems of many of these 12V DC based outlets, is very few give the full 85W power required for the many of Apple's notebooks. Make sure it is giving you a full 85W. If it doesn't, then it won't keep it charged. Note: As any Classical Physicist knows, Watt is power, Amp is current, Voltage is merely potential power.

a brody wrote:

Make sure it is giving you a full 85W.

How could you check for this without a breakout box?

We returned to the boat after 3 months. I plugged in the computer. It worked fine for about 2 days. Then it stopped charging. I plugged it in at the Yacht Club. It charged immediately. Took it back to the boat. It would not charge no matter which power source I used.

Could it be it's because when you arrived at the boat after three months, the laptop was fully charged?

If you top off the battery using land power, and then go to the boat, will the laptop work?

If that's the case, then charging the battery is just drawing too much power, or creating some other circumstance that makes the Apple charger act finnicky.

I stand behind my original solution. Whichever way you turn it, the problem is the combination of boat power and magsafe charger. I think it would be interesting to remove the charger out of the equation.

Just a tip which might be useful when researching this problem. If you download iStat Menus then you can view the power that the laptop is drawing, see screenshot, especially the "DC In sensor" at the bottom:

And I with mine.

Also, have you tried with a different charger? Just in case that particular brick is marginally defective.

"...your flippant "use what works" doesn't work!"

Yet, you marked the response as "this helped me". I'm confused about that. Too, I'm confused about the method by which you're trying to charge your computer. You posted lots of words about votages and AC and DC, but you don't state clearly how you're trying to charge yuor computer.

I fail to see how you can charge the computer with 12VDC. If you have 120-240VAC @ 50-60Hz, you can charge the computer through the power adapter. Regardless, you mentioned that the computer will charge for 30 minutes, or so, and then it stops charging. How do you know if the computer is charging initially? How do you know that the computer stops charging? Are you basing the charging/not charging on the color of the power adapter LED? Let's see if we can move this along faster the the current glacial pace. The power adapter has several protective corcuits that prevent damage to the power adapter or the computer. On the DC output, there's over-voltage, over-current, and over-temperature. If the power adapter shuts down because of that, you'll need to unplug the power adapter from the computer for 30 seconds, and then reconnect the power adapter to the computer. On the AC input, there are also protective circuits for several input voltage happenstances. Again, if the power adpater shuts down, you'll need to reset it, as mentioned earlier. It would probably behoove you to get a "line conditioner" that helps alleviate the input voltage problems, and it shouldn't cost more than $100US.

Well I can't say for sure, but there has to be some sort of fluxuation in power somwhere along the lines that is causing it to not have a steady current to charge the system. I don't know exactly what in the line is doing that but if there is no inverter installed it is really weird. I know that some inverters don't supply power like they should and when it comes to charging things they act all weird. However, as you stated there is no inverter in the line. The only thing I can think of is the water safe outlets like you were saying could be causing the problem. There is one thing you could try and that is something along the sorts of a power conditioner or a UPS type thing. I can't guarantee that this is going to fix your problem, but it is a place to start. Maybe if there was conditioned power that would level out any fluxuations in power the power adapter may start charging the computer for you. I used to be an electrician so I can tell you that it is some sort of power fluxuation that is causing the problem, but what is causing it, I couldnt' tell you. Just thinking that if you put some sort of conditioner in it, it may be able to take care of the problem that you are having. A UPS can do this by using the battery that it has internally to keep a steady voltage to the computer. A power conditioner does this using capacitors that will level out the power for you as well. If you can't get it to work while you are on the dock, you really are going to have problems when you leave the dock and are relying on the power coming from the boat.