Laptop power

[ysabelsdad]

I have been using a laptop computer for navigation on my sailboat I'm not happy with the way I'm powering it. I have been using a relatively cheap inverter plugged into a cigarette lighter socket. This work fine as long as the boats batteries are topped off or the engine is running. I have tried a couple of small inverters and they all seem very intolerant of low voltage conditions. Once the voltage drop below about 12 ˝ volts or so, the inverter starts sounding a very annoying alarm.

So my question is: are more expensive inverters more tolerant of low voltage conditions? Also you can buy things called DC-to-DC converters for laptops. Do these work any better?

[JouvertSpirit]

Google the string:
laptop car adapters

[wind_magic]

Yes you want to keep it all DC if you can, it's wasteful to convert to A/C and back again. What voltage is your laptop ?

[sailingdog]

Using a small inverter to power a DC-powered laptop is pretty inefficient. Most newer laptops use voltages above 12VDC, so you will need a DC-to-DC converter, but there are plenty of them out there. iGo, Targus, APC, and about a hundred other companies make them.

The only laptops that I know of that will have trouble getting one are the new Mac laptops, as no one has developed a "Magsafe" compatible connector that I know of other than Apple.

The better ones will be able to supply your laptop with power with input voltages of as low as 9 VDC.

[Idiens]

I use a DC to DC power supply for my Dell. However, although the PS is rated at 120W and has the correct three pin plug for the Insperon, the computer recognises that the device is not Dell and complains that it is not getting enough power. But it doesn't stop it working, so maybe it's just a marketing complaint.

[bestfriend]

SD - For mac you can use these. They do not draw enough power to charge the battery while using, but will allow you to keep up and running. I think a regular car charger will fry your mac because it allows surges.
http://store.apple.com/1-800-MY-APPL...nMore=MA598Z/A
http://www.cyberpowersystems.com/CPS140BI.asp

[hellosailor]

Idiens, there is no way that a Dell computer (or any other) can tell what brand of power supply you have connected if it is using 'just' a power connection. On the other hand, it is quite possible that your laptop needs more power than your power supply can put out. Laptops used to break into 45-vs-75 watt classes, but the newer more powerful chips can require supplies that are rated well beyond 75W. And, a supply needs to be rated for nearly twice what your laptop consumes, if you expect it to operate the laptop and charge the battery both at the same time.
So it is very possible for a generic power supply to be problematic, and equally possible for your Dell to complain "I'm not getting enough power" but make that into a lying marketing pitch by saying "The supply isn't Dell!" instead. Don't believe a word Dell says unless a more reliable authority confirms it.

Y'sdad-
Many DC power supplies (dc-to-dc, or dc-to-ac inverter alike) are designed to run from a car or boat alternator, which puts out 14.4 volts. A fully charged battery only puts out 12.6 volts under load, and it simply costs more money to build one supply that will operate under a wider range, i.e. from the 12.1 volts of a half-charged battery, to the 14.4 of a running engine.
Which also assumes the wiring to your power outlet is heavy gauge enough, because typical wiring may cause voltage loss under load, which cigarette lighters don't mind--but inverters do.

So you need to look at specs and devices, see which will operate over a wider voltage range and what you are willing to spend. You can buy a "buck booster" or dc voltage booster, which will provide 14.4 volts even from your battery, and that will make many devices (radios & computers) much happier. Or, a plain dc-to-dc power supply for the laptop like an AirPort (from Targus or Kensington or others) which works fairly well, and is smaller and not as versatile.
Using a small inverter (quality really varies with the maker) and a second Ac-to-DC laptop "brick" wastes power twice, so it works but isn't efficient.

Your mileage and budget will of course vary.

[Valiente]

Further to what Hellosailor noted (and this is very good information for those of us contemplating laptop navigation/plotting), I suppose another way to do things is to charge the laptop from the ship DC *only* when the engine is running and the alternator is providing that 14.4 or more VDC. When sailing, you can simply run for quite a while on laptop batteries alone...because realistically, you don't need the nav program on ALL the time in most situations. Laptops are pretty good at various modes of standby/powersaving, and you can radically extend the battery "up time" via power management.

My Dell Inspiron 8200 (which will be "retired" from graphics design duty to become the nav station PC shortly) has two LiOn battery bays that generally run for nearly eight hours in "normal" mode. Were I to shut off the monitor in favour of a 12 VDC LCD screen of the RV type, I could no doubt get more time in standby mode, and just touch the mouse or a hotkey to spin up the hard drive for a navigational query.

I would likely carry that DC-DC converter with "boost", anyway, but the reality is that I would just as likely cultivate the habit of not having the thing on all the time. I use a handheld GPS with a 12 VDC ship's power connector, and that and the paper chart is fine for 90% of my needs. I wouldn't even need that in the open ocean...I'd just take a fix a couple of times a day.

[btrayfors]

Ysabelsdad,

Here's what you're looking for.

Most DC "car" adapters will only work when the batteries are fully charged and/or there's a charge on them, as when the motor is running.

However, you can get a power supply for your laptop which will work very well with low battery voltage. The best source I've found is Lind Electronics. They make several models. I have one and it does very well down to about 10.5 volts or so, providing the 18VDC my IBM laptop is looking for. I have two other IBM power supplies which DON'T work well with low voltage: they'll run the internal battery down. The Lind charger will charge the battery even with low house battery voltage.

Call them to be sure you've got the right model.

http://www.lindelectronics.com/

Bill

[ysabelsdad]

Thanks for all the replies. I think I'll try the Lind DC-DC adapter for my Dell.

I spent last summer cruising the pacific northwest with my current setup. The PC based navigation is particularly great for two things. The first is planning. That's not a problem. The second situation is when you are coming into a unfamiliar anchorage or harbor, it is great to be able to glance at the laptop and see exactly where you are. If the laptop is hibernating, it will take a while for it to come back up. This is a problem. So while in deep water, I mostly keep the laptop powered off. I have the route loaded into the GPS and I keep a paper chart book close at hand. When I am heading in to harbor, I want it all ready to go at a moment's notice.