Inverter or laptop power adapter?

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 use.
Thanks for any help
Ron
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no_one wrote:

Tell him to just go buy a honda generator or something similar that can power a bunch of things.
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too small a boat; not a good solution but thanks

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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.
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Bungalow Bill wrote:

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.
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Michael A. Terrell wrote: <snip>

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 relay contacts.
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Palindrome wrote:

All of the models I use monitor the AC line quality, and use a microprocessor to decide when to switch.
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Michael A. Terrell wrote:

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 anything <1kVA.
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Palindrome wrote:

I work with small UPS from 250 VA to 850 VA, and I haven't been able to trick any of them into starting without clean 120 VAC 60 HZ input.
The last large one I worked with was 15 KVA, and had a switch to start it with no 208 VAC 3 phase input. Of course, that beast would sink a small boat. They had ot move it with a fork lift, then install the batteries: 20, 12 VDC UPS wet cell batteries.
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On Mon, 17 Sep 2007 06:49:37 -0400, "Michael A. Terrell"

Idiot. When they have clean power they DO NOT start at all.
It is when the power sags or fails completely that they begin to perform their job. D'oh!
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We are using plenty of UPSs where the inverter runs all the time. What you say could be true for a Standby UPS, however I suspect that even then the inverter is actually active, it's just not supplying power to the load. An on-line UPS will have its inverter actively powering the load all the time the UPS is switch on.
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Stephen wrote:

These are all off line UPS.
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wrote:

So MGE are not telling the truth?
http://www.mgeops.com/index.php/products__1/230v_products/ups/pulsar_m
[quote] Modular on-line double conversion UPS. Ideal protection for Servers, data storage, network equipment, Telephony - VoIP & Medical equipment - Industrial processes.
* 2,200 / 3,000VA (2/3U) * True On Line * 0.9 PF * Modular UPS * Hot Swappable batteries * 2 Load segments * USB and RS232 ports [/quote]
Maybe I should confront them about it, do you think?
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Stephen wrote:

I suspect that they already know that UPS come in three flavours: line-interactive, online and oiffline and that various manufacturers make different types - some producing all three types.
Even within each type, there are very many different designs. Designs for medium sized (2kVA<>10kVA ) tending to be rather different than those <2kVA and >10kVA.
The poster you are replying to seems to be talking about his experience with <1kVA units. Units that I rarely see so am quite prepared to accept that they are difficult to get to start up without a good supply. I can see that end of the market being very price-sensitive, so extra bells and whistles, like a start button are not worth including. Also, I assume that they mostly have very limited run time and are only intended to smooth out power glitches and shut their systems down gracefully - not run the system for tens of minutes/hours during an outage. So not much use as a battery+inverter when no supply is present, even if they could be started.
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Palindrome wrote:

Who would put a 10 KVA online UPS on a small boat? It might weigh more than the boat, itself. :)
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Michael A. Terrell wrote:

One of the main manufacturers of floating gin palaces is just down the road from me, in Plymouth (UK):
http://www.princessyachts.com
OK, not exactly "small boats". But they have oodles of amps...
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Palindrome wrote:

I installed a dual battery systems on a pair of paddlewheel boats at Lesourdsville Lake, an amusement park in SW Ohio in the early '70s. They insisted on using a 12 VDC to 120 VAC motor generator to run a tube audio amplifier, and a broadcast cart deck for music. If the boat's engine was shut off for more than ten minutes it wouldn't start. I couldn't convince them to switch to 12 VDC 8-track or cassette decks, so they spent about $1000 to buy two deep cycle batteries and two dual chargers, plus the golden time labor to have them done for an after prom party. We worked all night to get the two boats ready, and we were just leaving the dock when the carloads of kids started to show up.
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snipped-for-privacy@earthlink.net says...

Well, ballast is often made out of lead. ;-)
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krw wrote:

So are balloons! ;-)
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snipped-for-privacy@earthlink.net says...

Been to one of Dimbulb's parties?
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