pc chart display

[hellosailor]

Typical laptops consume about 45W of power. The ones that use a Pentium4 or other non-mobile chip (and Intel warned them not to build laptops with that chip) will burn 75W or more. So if your laptop doesn't use a mobile chip...you've got a problem.

The DC-DC power adapter is a MUST, as others have said. Try Kensington or Targus, and sometimes you can find them on eBay for $30. They are also sold as "air power" adapters, same adapter is used on commercial airplanes.

If you go into the power management features on your laptop, and set it up for maximum power conservation, you can cut your power consumption in half. The laptop can and should be powering down the hard drive and other drives, and if you have accessories you can often manually power them down as well. Some laptops let you manually shut the screen (certainly if you close the lid!) but unless you're interactively piloting the boat...dim the screen (cuts power to half of what is used with a bright screen) or shut the screen down (cuts entire power consumption in half).

There are many ways to skin the cat.

Bottom line...for what real paper charts cost? You can buy a dedicated deep cycle battery for the laptop. A Group31 for $125 or so should give you 100AH of power, and that should give you 20+ hours of laptop run time using a DC-DC power supply. That's cheaper than almost any other option.

[Canibul]

what a great idea, a dedicated battery. Simple and effective. And it means that you have a spare should your starter battery ever go tits up. Thanks for that.

[sundown2]

I appreciate everyone's input to my questions - I hope no one felt I was slagging thier replies.

Hellosailor: I like the idea of a dedicated battery - that would give peace of mind. It is funny that I did not think of that because an insurance company I used to deal with required at least one VHF radio be on a seperate battery. I must be getting old.
With reference to dc to dc power supply: is this what you guys mean ?
kensington Universal car/air power adaptor 33051

(sorry I can not seem to copy a link to the above product)

[hellosailor]

Sundown-
"kensington Universal car/air power adaptor 33051" EXACTLY!
Do check that it supplies enough power for your lapop model though, and that it comes with a matching tip for the power cord. Mine is a Targus, and when I opened it up to find out it didn't have the tip I needed, I called them up and the customer service rep said "Well, if you just bought it you shouldn't have to BUY another set of tips, why don't I just send them to you first class at no charge?"

Kensington are known for some of the best customer service on the planet. Like I told the nice lady, I'd make sure other people found out about that.

[Canibul]

I remember now, that mine was a Targus, as well. It had the adaptor for my Sony laptop, at the time. I used it a lot with the engine off, sitting in a cab waiting for a fare. never had a problem.

[sundown2]

Thanks everone for all the help. I am not sure which make/model laptops I have on the boat but I will check in the morning then order Kensington adaptor if they have the right ends. [IMG]images/icons/icon14.gif[/IMG]

[sundown2]

In the interest of General Information this is an excerpt of an email from my brother (who is an electronics tech) in response to my query of "how efficient is it to drive my via an inverter"?

evry time you convert ac to dc or back, you can figure on losing 10% of your power to heat. So taking 12 volt through an inverter to 110 and back to 12 volt will result in a loss of 15 -20%
I have never dealt with dc to dc but it sounds better. Take your input voltage times your input current and that gives input power. Now take output voltage times output current and that gives output power. The difference is the loss to heat. Now mutiply the difference and that gives a figure with a little less manufacture BS.

I have not done the math yet but he has lots of years of experience so I trust he knows what he is talking about.

[foxglove]

Yotfix has my vote. Use dead reacon, TVMDC, take LOPs, adjust for set and drift and leeway form wind to find course to steer.

GPS, if you have it, should always be on and available for confirmation. In fact, the law for professional captains is that all nav equipment on board must be in working order and available when underway.

[Canibul]

sundown, your brother's simple explanation makes a lot of sense. Everything in that alternator-battery-inverter-converter-dcbatts gets warm when operating. SOMETHING is sure being converted to heat and it aint seawater.