A friend lives on a boat with 12V power when he is not at the dock. He
needs to run his laptop (dell inspiron) while out at sea. He had problems
with a Radio Shack inverter (no suprise here) that finally blew itself up in
a large puff of smoke. His options are a new (hopefully better quality)
inverter or a laptop power adapter that runs from 12 volts and produces the
correct DC power to directly supply and charge the laptop. I have been
looking at names like Cyber Power and Targus and they seem to have suitable
units for the job.
Any opinions on which is the better solution? It seems to me that the DC-DC
(adapter) would be simpler than the need to chop and form 115vac which will
go to still another adapter to provide the DC that the laptop actually will
Thanks for any help
Define "better solution."
A laptop adapter that connects directly to 12v is more efficient, requires
less parts and cables that can fail, and can be used in practically any
vehicle. I got one on Ebay that works great, but it's only for the low
power laptop. My big pretty laptop requires more power than most of the
adapters I've found.
However, your friend lives on a boat, so having a handy source of 110v would
be useful for other things without the need for more adapters. Years ago I
got a good inverter at a truck stop, but if you want to go fancy, tripp-lite
makes some really nice ones which can be wired into an entire circuit or two
throughout the boat using marine Romex.
By the way, avoid Radio Shack unless you want a cheap battery or something.
Practically everything they have now is pure garbage. Even a cheapo
inverter should shut itself off or trip a breaker when overloaded. Buying
anything else from them is a waste of time and money.
Good feedback, thanks. I have the same opinion of RS and wanted to steer my
friend clear of them in the future.
What about power quality of the inverter output? Should one be concerned
or do modern inverters provide a clean enough output for laptop and other
uses? Any problems driving motors (refrigerators, fans, etc) within the
wattage limitations of the unit?
Most UPSs for computers utilize 12V battery systems inside them.
You could take a small, fully charged UPS onto the boat, and turn it on
when needed, which should yield at least a few hours of 120V operation.
You'd have to mute the alarm though. It would think it was operating
during a power outage, and the batteries are made for such deep cycling
type operation. Perfect solution.
Laptops and anything else with a switching power supply will be perfectly
happy with just about any inverter.
Some motors, on the other hand, might not be so easygoing. I haven't had a
problem so far, but I don't run much of that stuff on mine.
Instead of the curvy pretty sine wave you (should) be getting in the house,
an inverter will spit out what's called a modified sine wave, which kinda
looks like rectangles. Most things don't care, but I'm told some do,
especially motor type stuff. As I said, I don't do much more than running a
TV and whatnot off my inverter. You can always do the buy-and-try method,
where you buy something, try it out on the inverter, and if it doesn't work,
take it back.
If you want the pretty-sine-wavy inverter that'll run anything, it'll cost
you roughly double or more, and in my opinion, just isn't worth the expense
What you and your friend need to do is sit down, make a list of everything
you want to run, then do some research into what's available and what power
it requires. You can get quite a few things to run off 12v, like a fridge,
fan, coffee maker, and buying a huge, beefy inverter to run that kind of
stuff is a waste of money and power.
Oh, and when you see a 500 watt inverter for sale cheap, chances are almost
100% that it'll barely handle 200 watts or so for any length of time.
Sometimes they beef up their advertising by claiming Peak Watts or Surge
Power, and sometimes they just lie their tails off. Even if it can handle
500 watts, and you have something like 450 watts you need to run, better
move up to a higher rated model. It's best to have plenty of wriggle room
for start-up loads, unexpected demand, and the fact that few inverters take
kindly to being pushed closer to 80% of their max rating for any length of
Sure it will. I have a pile of UPS that will not work that way.
They have to detect the loss of the line voltage before the inverter
will tun on. Another type of power supply you know nothing about. If
your half assed idea was any good, I would have had lights for the two
weeks of waiting after the last hurricane damage to the local grid.
Thanks for the input; I was concerned that the square wave outputs could
cause stress on the load device but you have convinced me that that should
not be a concern with this application.
I agree with you that if it appears to be too good a price then it probably
Many do. Many do not and have a run switch that will start up the UPS
without any mains supply. Those that don't are usually fairly easy to
modify so that they will start up without a supply present. A typical
mod is as simple as a momentary-action switch wired across a set of
I saw somebody suggest a generator. These can be very small and handy, but
they can be hard on your gear. Typically, the cheaper or junkie the
generator, the nastier the output, usually in the form of messy sine waves
and voltage spikes. I had one do this, and it wasn't even cheap or junky.
Evidently it wasn't designed for 110v AC, but to run A/C units and recharge
the batteries on a 24v bus (the generator had it's own battery and used
12v). It tended to blow fuses on 12v adapters, such as cell phone chargers,
and killed a wall wart powering my DVD player. The conversion was done by
good mechanics, but the generator just wasn't built for this stuff.
Another problem with gas generators, especially if kept strictly for
emergencies, is fuel. If you leave it in there for months or years at a
time, it can do damage to the carbs, and you may be out of luck when you
really need it. The fuel can also go bad if you don't use stabilizer, and
eventually even that will go if not used. If you use a generator on a
regular basis, however, it should be pretty reliable.
Anyway, a small generator might not be a bad idea. You said elsewhere the
boat was too small, but if your thinking of a small refrigerator, it's
probably big enough for a smallish generator to power it. Higher power
gear, such as a fridge and fans, won't be bothered by a generator's output
as much as electronics, and you can still use an inverter for the more
delicate stuff. This would be handy if you go camping or have an emergency.
I still prefer an inverter, and eventually I'll get a more powerful one for
emergencies unless I get a great deal on a diesel genny. An inverter can
sit ignored for years and still fire right up. All you need is a fully
charged battery (or two, or several) which can be had with any car or truck.
This makes more sense for my lifestyle.
I tried using one of those small, cheap UPS's to power my cordless phone
during a power outage. When the power finally went out (stupid me didn't do
a proper test beforehand) I found the UPS died after just a few minutes.
With the biggish battery (12v 7.5mah) compared to the load (110v 500ma), it
should have lasted several hours, if not days. Evidently it automatically
turns itself off after a very short while, since it was really meant for
computers with heavier loads. This makes sense, since it was designed to be
cheap, not efficient, so instead of monitoring the load and battery, it just
had a simple timer.
The batteries in most UPS's, especially those designed for home or office
use, have sealed lead acid batteries. Not quite deep cycle, but they're
usually good for three to five years. (No doubt somebody's ready to fire
back that they have SLA's or AGM's that have lasted 15 years...good for you,
but their rated life is roughly 5 years or less in terms of reliability) In
most UPS's, you can change out the batteries after a few years at a small
fraction of the cost of a new UPS.
Some UPS's are designed to be directly connected to larger, automotive type
batteries, so if you need very long running time and/or high power, these
are the way to go. Typically, you would use deep cycle marine type
batteries, and some can run on anything from 12v to 48v.
Even the swish ones that do a lot of line quality monitoring will start
the inverter up when plugged into an out-of-tolerance supply. The
/supply present/ signal to the uproc is often either an opto-isolated
logic level or a relay contact. Faking one of those with a momentary
contact switch will get the uproc acting as if it has a supply present
and it will start monitoring the input supply - which, with no supply
present will cause the inverter to start up.
Another thing to look out for is a (test) jumper on (one of) the pec(s).
I haven't come across a modern one without one - although I seldom see
Bullshit. I have UPSs that will turn on in backup/recover mode when
there is no AC power detected, and if it ain't plugged in, guess what,
asswipe... no AC gets detected, dipshit.
Another power supply that YOU made a retarded ASSumption about.
Par for the course with a weenie fucktard like you.
IME, for modern UPS, *some* will do something similar but certainly not
most - as due to what I can only assume is a cost-saving measure, they
often don't have a "test" or "start" button. So they just sit there
doing absolutely nothing until connected to a supply, no matter what
position the main switch is in.
I haven't actually come across one that runs immediately on operating
the main switch, with no power connected. A make and model of one that
does so would be appreciated. The nearest to that I have seen is one
with a "start" button, right next to the main switch.
Another thing for the OP to consider is that UPS tend to use several 12v
batteries in series, to create an internal dc supply of 48v or higher.
Whereas an inverter is usually designed to run off 12 or 24v. So an
inverter can be a whole lot easier to hook up to the odd big deep
discharge battery, or even a car battery or two, at a push.
Also many small UPS have been designed only to run for the length of
time determined by their internal batteries. On high load they get very
hot internally, but the battery energy runs out before the internal
temperatures rise to unsafe levels. Mod those to run off an external
battery supply and they trip thermal (often non-resettable) fuses - if
you are lucky..
Me, I like to use a genny and an inverter and batteries- especially
these tiny ones that use electronics to produce the output sine wave and
allow the motor speed to change with load. Even a small one will work
well with a battery/ inverter combination. Whereas you need a much
larger regular genny to do that, because of the voltage peak truncation
effect of load on small gennys.