Join Date: Aug 2006
Location: Arlington, VA
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Laptops eat a lot of power, whether or not you run them on DC. Yes, there's some savings by going with a DC power supply, but it's not as much as you'd think or hope. Tweaking the power settings on your laptop is a good idea, though, and will help somewhat.
Further, most laptop "car adapters" are designed for use in cars where the motor is running (producing in excess of 13.2VDC). With the typical house battery bank on a sailboat where voltage is only above 12.6 when the motor, generator, solar panel, or windgenerator is running, these devices typically will not charge or maintain the laptop's internal battery. There are specially designed power supplies which will work down to 10VDC input, e.g., those from Lind Electronics, but they're $80-100 or so.
Re: uploading waypoints and routes to your GPS, I think that's a good idea and routinely do so on my boat. I have two identically programmed Furuno GPS units, one at the helm for the helsman and another at the nav station which is connected to my laptop for chart display and tracking (I use Maptech's Offshore Navigator). This arrangement has worked flawlessly for several years.
Re: hooking the GPS up to your autopilot, I think that's a very BAD idea. While it seems like a smart thing to do, in the end it is likely only to increase the occurrence of "GPS-assisted groundings". GPS errors can and do occur, as do charting and plotting errors, computer errors and -- worst of all -- human errors. My advice is to use GPS and all the toys as INPUTS (among many others) to a navigation system which YOU control and monitor, not as outputs to your rudder.
By all means keep a running DR plot, and regularly record your position. Those who don't do this are simply courting disaster.
S/V Born Free