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Old 08-07-2009, 18:19   #1
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What Inverter for Computer?

I have a desktop computer on the boat (with lots of video editing, music, etc.) and would like to power the 120v ac computer from the batteries using an inverter (hopefully eleminating inteferance from pumps, inverters, chargers, refrigerton, alternaters, etc., etc.) My question is ....... Since the 120v ac power goes to a power supply in the computer which converts the power back to a lower voltage dc power, how imporant is it for the inverter to be trusign or the cheaper moified sign wave?

Any input would be apprciated .............. Bill A.
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Old 08-07-2009, 18:27   #2
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The topic has been around loads.. the consensus seems to be to get a regulated DC-DC inverter to supply the laptop with the voltage it requires.
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Old 08-07-2009, 19:08   #3
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I don't believe this subject has been talked about at all. Probably because not many boaties carry them because of space limitations for a desktop. My guess would be that a modified Sine wave inverter would work fine. Now for a laptop you definitely need a pure sine wave inverter. One of the advantages of a desktop is that parts are available everywhere as opposed to a laptop where any single part going bad signals a deathblow. The bigger issue would be how robust the desktop is compared to the laptop. How much pounding can one take?
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Old 08-07-2009, 19:21   #4
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Internal computer power supplies actually provide three different voltages to the computer motherboard and other internal components, 12 volts, 5 volts and 3.3 volts, all DC. The computers internal power supply input might be 120VAC, 12VDC or be a power supply which can accept a range of voltages of AC or DC. Most lappies now accept some sort of DC as their input. Your laptop where you plug in the external power supply will probably tell you this. Your owners manual will tell you this. The output of your external power supply (power brick) will also say so. If you are fortunate, your computers internal power supply will accept a range of DC voltages. If so, you can hardwire your boats 12VDC system directly to the input of your computers internal power supply. Internal power supplies have voltage regulators which control the three different internal voltages, so don't worry too much about 12 volt system voltage fluctuations unless your DC system is prone to large voltage spikes. If that is the case then I would purchase a regulated power supply which is powered by your 12 volt DC system that puts out whatever voltage your computers internal power supply requires as its input. Make sure it can provide the necessary current (amps) as well. The downside of a DC-DC regulated voltage power supply is that it costs additional money money and adds an inefficiency to your DC system.

I now have five desktops on the research boat that I run. In almost 20 years that I have had computers onboard a number of different boats, none have failed because they are in a salt air environment nor have any failed from vibration. Boats seem to be easier on computers than are people who carry computers around. If you need to move your computer off and on the boat frequently, then definitely get a laptop. Otherwise, I like Shuttle type computers because of their small size.

Another alternative would be to build your own desktop with a power supply unit (PSU) whose input is 12 volts DC. Unfortunately, most computer manufacturers have their own proprietary PSU's and it would be difficult to find a 12 volt version that would work although I have seen a few aftermarket PSU's that are made for Dell's. I have built a number of computers in case you were wondering.

http://www.powerstream.com/DC_PC.htm
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Old 08-07-2009, 20:41   #5
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Internal computer power supplies actually provide three different voltages to the computer motherboard and other internal components, 12 volts, 5 volts and 3.3 volts, all DC. The computers internal power supply input might be 120VAC, 12VDC or be a power supply which can accept a range of voltages of AC or DC.
And if it is an HP computer it may have a different voltage - grrr...

Had a PS fail and could not just go and buy a drop in PS. Had to buy the HP one at 3X the price. Got a new PC instead.

I like things to be multi purpose on a boat and would seriously consider a laptop/lcd replacement of the desktop. You may have occasion to want to drag the laptop ashore for doing mail etc.
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Old 08-07-2009, 20:53   #6
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I have had desktop 120 volt computers on my boat for 10 years. I have used them frequently and have never had a problem running it off a modified sine wave invertor.

You definitly do not need a pure sine wave invertor.

The reason is simple. The battery powered backup units that you plug your desktop into in case of a power failure are Modified Sine Wave Invertors.
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Old 08-07-2009, 20:57   #7
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And if it is an HP computer it may have a different voltage - grrr...

Had a PS fail and could not just go and buy a drop in PS. Had to buy the HP one at 3X the price. Got a new PC instead.

I like things to be multi purpose on a boat and would seriously consider a laptop/lcd replacement of the desktop. You may have occasion to want to drag the laptop ashore for doing mail etc.
I should have mentioned that all the major manufacturers use their own proprietary PSU's. Only when you build your own desktop from scratch can you buy a standardized ATX type PSU. Enough of those are made to be price competitive.
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Old 08-07-2009, 21:00   #8
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The reason is simple. The battery powered backup units that you plug your desktop into in case of a power failure are Modified Sine Wave Invertors.
Technically, its a modified square wave. It was never a sine wave. If it was ever a sine wave then there would not be any reason to modify it.

All inverter manufacturers are doing is making a square wave and lopping the square corners off a bit. They use a rather deceptive term (lie?) to describe it.
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Old 08-07-2009, 21:05   #9
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Thanks everyone,

I have a DESKTOP comuter which fits perfectly in the boat. I also have a laptop for when I want to drag a computer ashore. ..... Now back to the original question ....... If I use an inverter (drawing power directly from the house bank of batteries and only used for the computer) to power my 120v ac DESKTOP computer (rather than the the boats gen-set or house inverter (which is wired into the boats elctrical system and powers a watermaker, refrigerator, etc.) does it have to be a pure sign wave type or could I get by with a less expensive moified signwave inverter?

Again, thanks for your help and input, Bill A.
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Old 08-07-2009, 21:11   #10
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You can get by with a modified square wave inverter. I have done it before to run desktops when my true sine wave inverter crapped out. You may hear a little more noise out of the PSU because transformers don't run as efficiently on modified square waves, but there should not be any other troubles. Even with junk modified 120 AC, your PSU should be able to provide the exact voltages that your motherboard and other computer components need. I once cooked a "wall wort" on modified AC...don't know why it did not like it. Some electrical devices just don't work with it. All the computers I have ever plugged into it get along just fine with it though.

What brand is your desktop? You may be able to install a 12VDC PSU and not have to fuss with an inverter at all. That would save wasting battery power by running electricity thorough an inverter.
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Old 09-07-2009, 01:21   #11
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Laptop power bricks work fine with quasi sine wave (modified square wave) inverters.

Generally speaking the only time you need pure sine wave on a boat is for thyristor controlled devices such as bread makers, washing machines etc. Microwave ovens prefer pure sine wave as well, although will work with slightly reduced efficiency on quasi sine wave.

Having said that I have been running my laptop using a 120w DC to DC adapter from Walmart. Selection of voltages from 15-24v with a range of connector plug heads to suit virtually every laptop made. It has plenty of power in hand & rarely gets even warm.

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Old 09-07-2009, 04:48   #12
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A modified sine wave inverter will work fine for your desktop.
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Old 09-07-2009, 05:11   #13
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Quote:
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how imporant is it for the inverter to be trusign or the cheaper moified sign wave?

.

Hi Bill,

We have been told by people in the know that any inverter will be fine for the computer.

When we do use an inverter we use a VERY cheap 300 watt jobbie and its just FINE


However why dont you use a DC votltage changer called a "Notebook Power Supply"? t changes 12v DC to 19V DC or whatever your computer uses. Mine changes 12 v to 15, 16, 18, 19, 22, 24 volts.

Try that They are cheap and use less power than an inverter.




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Old 09-07-2009, 10:01   #14
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For a laptop I would say go with a DC-DC converter as mentioned above. The savings in lost electricity and lack of heat dissipation will quickly pay for it.

For a desktop, rather than invert to 110/220 then use the computer's heavy electricity-hungry power supply to convert to DC, just bring in a quality 12 volt lead ideally with its own dedicated back up battery. Then have three drop downs as listed above for 12v, 5v, and 3.3v. You could probably fit the whole contraption into the space normally occupied by the traditional powersupply.
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Old 11-07-2009, 08:25   #15
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mobeta,

Here's what I have for my desktop PC on the boat - an ATX-style 12-36Vdc input power supply from Mini-Box. Make sure you also order the SFX/ATX enclosure with fan, also. They have a wide selection of small-form-factor PCs intended for auto applications...

Like you, it is (was) a high-end desktop, with 4GB ram, an Intel Core2Duo at 2.3GHz which I use for video editing and MythTV. It's now considered a mid-low level desktop, I guess...
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