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Laptop Computer and Battery Power

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jotruelove
Deckhand

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USA
22 Posts

Initially Posted - 07/30/2006 : 11:25:36

Greetings again all!

I am sure thi stopic has been covered, but I could not find any data in the forums. So, in advance, forgive the repost!

While on my 85 Catalina 25 yesterday, I tried to use a 12V adapter on my Dell Laptop to run the computer off the 12V battery, only for the computer and the computer's power supply to ignore the effort.

I was using a fully charged (verified by VOM)12V deep cycle. Do I need two batteries? The 12V to 120V powers the computer just fine in the car. And though I know that is apples and oranges, I make the statement simply to validate the converter. I am not sure if it is an inverter or not.

Thanks, as always, for any advice given...

Fair Winds...

Jim

Fair Winds...

James Truelove
Pearl
1985 Catalina 25
Sunny Florida Panhandle

Edited by - on

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 07/30/2006 : 11:48:29

Jim,

I'd suggest you start by seeing if you can verify power as close as practical to the laptop while in the boat with everything connected.

If there's no power at the laptop, but you can verify 12V at the battery while the laptop is connected, that pretty much indicates the problem is between the battery and the laptop. If you're going through a cigarette lighter style connector, I'd start looking for a problem there. Those things are notorious for not making good contact consistantly.

By the way, if you have a choice of powering the laptop through either an inverter or a 12V adapter cable, I'd suggest you use the direct cable. Obviously all laptops (actually all computers) run on DC internally. If you can supply the computer with DC externally, doing so should improve the energy efficiency, and thus increase the amount of time before the computer runs down whatever battery it's getting power from.

-- Leon Sisson

Edited by - on

jotruelove
Deckhand

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USA
22 Posts

Response Posted - 07/30/2006 : 17:21:09

Thanks for the input Leon.

Might I ask you how would I feed the 12V from my battery directly to the PC? I realize the powersupply drops the 110 to the required DC, but I don't know how to get around the power supply itself.

Edited by - on

ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 07/30/2006 : 17:33:53

Leon probably has it:

"I'd start looking for a problem there [12V outlet]. Those things are notorious for not making good contact consistantly"

On my C25 the 12V outlet was fed with a seperate set of wires running back to the battery... and had a blown fuse.

Inverters (12VDC to 120VAC) are pretty cheap these days... one would make a nice accessory on a C25. You could just plug in your 'regular stuff'.

Edited by - ClamBeach on 07/30/2006 17:34:58

Jmurfy
Navigator

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USA
176 Posts

Response Posted - 07/30/2006 : 22:47:06

I have a 1985 catalina 25 and the 12 volt power/cigarette lighter works but the contacts are iffy. I also have an inexpensive inverter (about $40.00) that clamps directly on to my 12 volt battery. That works great for the lap top and other devices I have like a small tv.
Remember power (measured in watts) = volts x amps. More volts less amps and vice versa. Your only concern should really be the amount of power you pull out of the battery not whether its 12 volts or raised to 120 volts by a device like an inverter.

Edited by - on

ilnadi
Captain

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452 Posts

Response Posted - 07/31/2006 : 11:29:02

Couple of quick things:<ul><li>Do <u>not</u> connect the 12V from the battery to your laptop directly (even if your laptop uses a 12V supply). Any noise on the battery line will frappe the laptop for sure</li><li>The cigarette lighter adapters for laptops are still power supplies, they just do DC to DC conversion and regulation</li><li>The main advantage of a DC-DC supply for a laptop is that each of those boxes has an eficiency. When you cascade two (inverter+AC power supply) you lose efficiency. On the other hand most of those things are so efficient it probably does not matter that much</li><li>If you want to test if the power supply works, try the cigarette lighter plug in your car</li><li>Keep in mind that some of the newer laptops are smart enough to complain if you have an off-brand power supply</li></ul>

Edited by - on

stampeder
Master Marine Consultant

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1608 Posts

Response Posted - 07/31/2006 : 18:28:54

I bought a 300W inverter that I hook up directly to my deep cycle 12V house battery. I run my laptop off the inverter.
Simple. Easy to trouble shoot.

Edited by - on

lcharlot
Master Marine Consultant

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Antigua and Barbuda
1301 Posts

Response Posted - 08/01/2006 : 07:33:48

I have run my laptop in the boat off of a 175 watt inverter for up to 4 hours without noticeably depleteing the battery, but that was for only one day. The boat has a 50 watt solar panel, which keeps the battery topped up during the work week when I am not using the boat. If one were on an extended cruise and tried to run a laptop every day for two or three weeks, I would guess that a typical size 27 battery would only last a couple of days before needing to be charged. I think my inverter is drawing about 8 to 10 amps when the laptop is running at full capacity, like when playing a movie. A size 27 deep cycle battery with 100 amp hour reserve capacity will theoretically support 10 amps for 10 hours, but that's with a brand-new battery. A battery that is a year or two old will probably have no more than 2/3 of the capacity it had when new.

Edited by - on

jotruelove
Deckhand

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USA
22 Posts

Response Posted - 08/07/2006 : 08:04:09

Thanks for all the great advise. Here is how I solved the problem...

I already had in hand a quality 175W inverter that is 12V "cigarette lighter" plug based. After all the good advise, I bought a 12V adapter and hooked it right off the battery leads. Plugging in inverter to this new adapter powered the computer just fine.

I don't know if the 12V accessory that is in the boat has too much loss, or perhaps the other devices (light, fan, depth, radio, CD) is on the same circuit as the 12V accessory plug. In any event, I get to make a new run from the battery to the new nav and computer station (well, the cutting board over the stove, whatever you want to call it!)

Thanks for all the great words of wisdom. A membership to this site is the best boat accessory I have ever purchased!

Edited by - on

Frank Hopper
Past Commodore

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Pitcairn Island
6776 Posts

Response Posted - 08/07/2006 : 08:15:35

Sounds like a Nav Station to me!! And it sounds cool.

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Douglas
Master Marine Consultant

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1595 Posts

Response Posted - 08/13/2006 : 21:23:23

Why would you need an inverter. The lap top is only going to return any A/C you provide back to DC. What you need is a small step up transformer. Most lap tops are running of about 14 volts DC. These little step up transformers can be bought on E bay for under $30. Plug in to a cigarette lighter socket and your all set to play.

Edited by - on

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