Garland Gray II wrote:

Well now... I hadn't really considered that there was an inverter in my
laptop.

All laptops have something like that to stabilize, smooth and adjust the
input voltage and send it to a few major components, sometimes at
different voltages. Your laptop probably takes about 14V from your AC
to DC adapter and outputs 12V or so to the battery charging circuit and
has two other outputs (typically 5V and 12V) to the primary components
like motherboard, drives, etc.

To charge your 10.8V battery, you need a little higher voltage and it
needs to be stabilized and at a given amperage and the internal DC-DC
inverter takes care of all that. The charging voltage may be monitored
by the DC-DC inverter and tailed down or turned off when the charging
process is complete. Your laptop is probably running off the internal
battery at all times. When the battery is fully charged it stays fully
charged with the AC adapter connected.

If you can find the specs for the OEM DC-DC adapter your laptop, you'll
probably find it has an output voltage of 14 Volts or so (at a specified
Amperage) and that it will use an input voltage of 11-15V or so. So you
want a DC-DC adapter that will provide the same output.

So if I'm running it off the inverter now, the current would be going from
dc to ac to dc back to ac ??

At the end of the line, the laptop only needs DC voltages. The only AC
to DC conversion is to convert AC power to DC power for the jack on the
laptop. It does not really matter if that DC input power is converted
by an AC adapter or DC adapter as long as it is stable and at the right
voltage with adequate amperage.

The laptop will tolerate some variation in the input voltage, maybe a
volt or two or so. Then it changes that voltage as necessary and passes
it around.

The bottom line is that it is simpler to use a DC-DC adapter on a boat
that has 12V power available than it is to use DC to AC inverter so that
you can use your AC to DC adapter. Also the DC-DC process will use less
power, generate less spurious electrical noise (may bother radios,
radars, etc.), and is generally safer (lower voltages/less risk of
shock) in a marine environment.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

"Garland Gray II" wrote in
news:Zchxf.6624$CV.5318@dukeread03:

Uh Larry, how can I determine whether it is negative ground?
I've looked around on it and the battery. I tried to test the battery
contacts w/ my multimeter, but the probes were too fat, and I wasn't
sure I'd be more than guessing which was the ground contact anyway.
I called Toshiba support, and he couldn't answer that kind of
question.


Obviously, you're going to use your own 12V power cord after you figure
out which contacts on the plug are + and which are minus, right?
So....take the battery out so we don't blow the ohmmeter in your
multimeter with its DC, then measure from the + power wire to the shell
(ground) on the serial DB9 connector. If they are connected together,
it's positive ground. Try the same for the - power wire to audio and
serial ground.

I'm concerned about someone's comment their starting of the big diesel
blew a directly-connected notebook like this. Maybe all this is not a
good idea, after all.

Perhaps the $29 75-watt DC-to-AC inverter from any Radio Shack, which is
so efficient there's no fan and it's all built right into the plastic
plug, would be a better idea to plug your laptop's AC supply into. The
smaller the inverter, like this tiny one, the less its wasted idle
current drain. I doubt you could measure this little guy's DC unloaded
current without a milliammeter. Its LED indicator is probably its
largest idle load. Your notebook hardly draws 75 watts to charge the
battery and power the computer. If it won't, graduate to the 150W
version.

Got it..
And yes, I had taken note of Dennis' comment about voltage spikes. It
wouldn't be difficult, if the computer is plugged in, to switch off the 12v
outlet circuit before starting the engine, but that is something else to
remember.

"Larry" wrote in message
...
"Garland Gray II" wrote in
news:Zchxf.6624$CV.5318@dukeread03:

Uh Larry, how can I determine whether it is negative ground?
I've looked around on it and the battery. I tried to test the battery
contacts w/ my multimeter, but the probes were too fat, and I wasn't
sure I'd be more than guessing which was the ground contact anyway.
I called Toshiba support, and he couldn't answer that kind of
question.


Obviously, you're going to use your own 12V power cord after you figure
out which contacts on the plug are + and which are minus, right?
So....take the battery out so we don't blow the ohmmeter in your
multimeter with its DC, then measure from the + power wire to the shell
(ground) on the serial DB9 connector. If they are connected together,
it's positive ground. Try the same for the - power wire to audio and
serial ground.

I'm concerned about someone's comment their starting of the big diesel
blew a directly-connected notebook like this. Maybe all this is not a
good idea, after all.

Perhaps the $29 75-watt DC-to-AC inverter from any Radio Shack, which is
so efficient there's no fan and it's all built right into the plastic
plug, would be a better idea to plug your laptop's AC supply into. The
smaller the inverter, like this tiny one, the less its wasted idle
current drain. I doubt you could measure this little guy's DC unloaded
current without a milliammeter. Its LED indicator is probably its
largest idle load. Your notebook hardly draws 75 watts to charge the
battery and power the computer. If it won't, graduate to the 150W
version.

Thanks, Jack

"Jack Erbes" wrote in message
...
Garland Gray II wrote:

Well now... I hadn't really considered that there was an inverter in my
laptop.

All laptops have something like that to stabilize, smooth and adjust the
input voltage and send it to a few major components, sometimes at
different voltages. Your laptop probably takes about 14V from your AC to
DC adapter and outputs 12V or so to the battery charging circuit and has
two other outputs (typically 5V and 12V) to the primary components like
motherboard, drives, etc.

To charge your 10.8V battery, you need a little higher voltage and it
needs to be stabilized and at a given amperage and the internal DC-DC
inverter takes care of all that. The charging voltage may be monitored by
the DC-DC inverter and tailed down or turned off when the charging process
is complete. Your laptop is probably running off the internal battery at
all times. When the battery is fully charged it stays fully charged with
the AC adapter connected.

If you can find the specs for the OEM DC-DC adapter your laptop, you'll
probably find it has an output voltage of 14 Volts or so (at a specified
Amperage) and that it will use an input voltage of 11-15V or so. So you
want a DC-DC adapter that will provide the same output.

So if I'm running it off the inverter now, the current would be going
from dc to ac to dc back to ac ??

At the end of the line, the laptop only needs DC voltages. The only AC to
DC conversion is to convert AC power to DC power for the jack on the
laptop. It does not really matter if that DC input power is converted by
an AC adapter or DC adapter as long as it is stable and at the right
voltage with adequate amperage.

The laptop will tolerate some variation in the input voltage, maybe a volt
or two or so. Then it changes that voltage as necessary and passes it
around.

The bottom line is that it is simpler to use a DC-DC adapter on a boat
that has 12V power available than it is to use DC to AC inverter so that
you can use your AC to DC adapter. Also the DC-DC process will use less
power, generate less spurious electrical noise (may bother radios, radars,
etc.), and is generally safer (lower voltages/less risk of shock) in a
marine environment.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

An often over looked specification when buying a laptop for on board
use is how much power it draws. I met one fellow sailor last summer
that showed me his shiny new 17" wide screen multi - media laptop. The
shine had worn off as soon as he realized it was drawing more juice
from his battery than his fridge (ouch).

I bought a new laptop last spring. It is a high-end small display
Toshiba that is built for use on the road. Gel mounted HD, spill
membrane under the keyboard, magnesium case yada yada....

A month or so ago someone in the NG I subscribe to bought a "Sea PC".

Have a look he

http://www.seapc.se/index.html

If this had been available at the time I would not have bought a
laptop. A boat is not a nice place for any non-marinized electronic
device. This includes palm pilots, camcorders etc. The copper traces
on today's PCB are very very tiny. A small amount of (shudder)
corrosion and the device is dead and unlikely to be repairable. This
happens. Unless your laptop has been specifically made for the marine
environment you will eventually have problems due to air borne salt
laden moisture.

Personally I think the 8.5 in. version looks real tasty....


Hope you find this useful, and nope I have nothing to do with this
firm (sure would like to though), however I have contacted them by
e-mail. All of the main players in the company are sailors. Cool
product, prices with high-end laptops but much lower than "tough book"
type of gear.

regards,


Capt. Ricky Spamson

(to reply leave spam IN my e-addy, the spam bots drop the word spam)
Works for everyone except about 7400 deposed Nigerian Generals (:-)

Another location for low power hig spec. boat PC's is

http://www.mini-itx.com/store/

They are geared to the car PC but you can use on-board equally.
I have no connection with the owners of the link, but am a satisfied
customer.

A boat is not a good place for a laptop.


have a look he

http://www.seapc.se/index.html


I bought a laptop last June ($2800 Toshiba). Had the Sea PC been
available at that time I would have bought one instead. When you are
checking "specs" pay attention to power consumption. Many laptops
today (especially the 17 in. "media centers") draw more juice than a
fridge. Another huge consideration is how well will a laptop hold up
under marine conditions and exposure to moist, salt laden air? The Sea
PC is rated to take a stream from a fire hose. The costs, from what I
have been able to determine are comparable to a high end laptop.
.................................................. .................................................. ...

Another location for low power hig spec. boat PC's is

http://www.mini-itx.com/store/

They are geared to the car PC but you can use on-board equally.
I have no connection with the owners of the link, but am a satisfied
customer.

i'm just responding to this thread in general, not to the specific post
i hit reply to.

i think the perfect laptop for a boat is the 50-100$us one you get from
ebay, the old toshiba is my choice. yes i know! crazy you say, who
wants an ancient laptop when there is so much new fancy stuff out
there. surely you must have the fanciest best one since you are the
fanciest and best. well, let's consider that ...

- you won't worry when onshore if someone is stealing it
- how much cpu power does it actually take to do gps maps, not much!
- it has real serial ports on it instead of incompatible usb/serial
converters
- it's really inexpensive, meaning you can have TEN of them, one to use
everyday and NINE backups if you want
- it has an easy to replace widely available hard drive
- you can get more memory for it on ebay too
- it is ok if the natives spend days playing tetris on it and get
citrus juice on the keys
- you can move the hard drive to another computer if the laptop dies
- or you can take the drive out altogether and make a diskcopy of it
- if it dies due to salt air, who freaking cares, get another one
- if your boat gets hit by lightning and it dies, who cares, get
another one
- how much cpu power does it take to write email anyway
- if the king of bunga bunga bunga really likes it ... well, just give
it to him
- you can leave it onshore in your hotel room without worrying about
someone taking it
- you can hike it through the jungle and not worry if it gets rained on
- you can use it on deck without worrying about the sun damaging it
- it is ok to loan it to someone and not really care if they give it
back
- did i mention you can buy TEN for the price of ONE cheap new one ?
- you can buy a few of them and still have money left for backup radios
and backup gps
- you can experiment, who cares if that HF tuner puts out so much RFI
it burns it up
- it's ok to dance pagan dances around it, ok, well, i guess you can do
that with any laptop
- you can ride with it on a bicycle and not worry about vibrations,
because, who cares
- it's ok to let kids play with it, because .. who cares
- nobody gets yelled at for touching it, so, they never figure out just
how much of a jerk you are
- when bored you can play "slide the laptop" across the deck and giggle
and snicker
- you can dress it up with feathers and fur and things and it won't get
angry
- it is ok to sit your drink on it, or your sandwich, like a small
table
- you can have fun on your trip instead of being a little laptop nazi
- if it breaks you can actually take it apart and fix it (try that with
a new one)
- an old laptop is gracious, happy not to be sent to the island of
misfit laptops where the abominable snowman lives
- you can make up stories about how many times it has saved your life,
and people might believe them
- it has an actual real printer port on it (not just usb), a printer
port that is compatible with printers all around the entire world
- it has an actual floppy drive on it, compatible with floppy drives
all around the entire world
- if it's stormy and water is splashing around you can put the laptop
in a clear plastic bag and play solitaire with it in between reef
changes and still keep a watch
- etc, etc ...

i think if you spend some time considering the merits of the 50-100$us
ebay boat laptop you will come to see the great wisdom of it.

Once you get to around 1gHz there's not much more you need for an on-board
laptop. At that CPU speed you're at least up to handling things like DVD
playback, so you can get multiple uses out of it as a chart plotter and a
disc player. Same thing goes for mp3 music playback.

One really good suggestion is pulling the drive and copying it. With the
money you'd save on a cheapie laptop you can get a pair of two new drives,
setup one of them and then make a copy of it. It might get a little geeky
for some folks. But you can get laptop to desktop IDE converters and then a
USB to IDE converter. Some USB converters already have a laptop-style
connector on them, making it even simple. Then you can just put the two
drives on a desktop via the USB port and copy one drive to the other.

Combine two new drives with two used 1Ghz laptops and you'd really have
yourself covered in the even one breaks. And it'd probably be cheaper than
just one brand new one.

Getting new drives is a great idea, for two reasons. One being the new
drives, at 7200 rpm, are sooo much better performance-wise than the old
drive. Just putting in a new drive with that faster rotational speed can
make an old laptop seem nearly new again. Secondly you get better shock
protection in most new drives. The old ones were good but the new ones are
amazing. The fact that you'd get a gargantuan amount of new storage space
is almost an afterthought. Just make sure your old laptop can handle a
bigger drive. If it's a 1gHz machine it'd be very likely to have no trouble
with any new drive sizes. But old/slower ones might.

Oh, and pickup a spare battery, a NEW one. They wear out.

-Bill Kearney