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Old 16-11-2013, 11:05   #301
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Re: 12vdc Marine Computers

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Originally Posted by bfloyd4445 View Post
I think you are spending $10 for a device that does nothing but allow you to plug the computer into the 12vdc socket.
DC to DC converters are nearly always more efficient than using an inverter in the real world.
It depends on a lot of factors, but typically a 30% improvement is seen.

I realise that for the DC to DC converter to step up voltage it goes through an intermediate AC phase, but unlike an inverter the voltage and frequency of this stage instead of being tied to a strict standard like 110 or 240v at 50hz can be selected for the most efficient conversion. in addition the output power is is limited resulting in further efficiency gains.

In general it is worth powering as much as possible on a boat directly from 12v if this is not possible DC to DC converters are much better than inverters at least until the power draw becomes very high.
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Old 16-11-2013, 12:15   #302
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Re: 12vdc Marine Computers

Well I cut class the day they taught electrical engineering so how about some of you smart guys recommend the best DC to DC converter for a boat. I have been using a plug in $US40 inverter I bought at AutoZone to power/charge my HP laptop. Is the $US10.40 on ebay a good one. I don't mind spending more for better quality.
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Old 16-11-2013, 14:09   #303
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Re: 12vdc Marine Computers

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Well I cut class the day they taught electrical engineering so how about some of you smart guys recommend the best DC to DC converter for a boat. I have been using a plug in $US40 inverter I bought at AutoZone to power/charge my HP laptop. Is the $US10.40 on ebay a good one. I don't mind spending more for better quality.
I have two marine rated small inverters each was around $40 dollars one of which I have used for over ten years with no problems. Both of mine are 400 watts The 400's I have both will support 800 peak and run my coffee pot and espresso machine with no problems.
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Old 16-11-2013, 14:27   #304
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Re: 12vdc Marine Computers

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Originally Posted by tomfl View Post
Well I cut class the day they taught electrical engineering so how about some of you smart guys recommend the best DC to DC converter for a boat. I have been using a plug in $US40 inverter I bought at AutoZone to power/charge my HP laptop. Is the $US10.40 on ebay a good one. I don't mind spending more for better quality.
I have one of these OpenUPS powering a Macbook Pro plus two more basic 12v/12v ( constant 12.8v out) ones powering an LCD screen and a Via PC...
Good kit... the one for the mac is a bit noisy on VHF... so I just turn it orf when sucking down a sat.... when I remember... you can see the diff here... when I remembered to unplug it........
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Old 16-11-2013, 15:33   #305
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Quote:
Originally Posted by tomfl View Post
Well I cut class the day they taught electrical engineering so how about some of you smart guys recommend the best DC to DC converter for a boat. I have been using a plug in $US40 inverter I bought at AutoZone to power/charge my HP laptop. Is the $US10.40 on ebay a good one. I don't mind spending more for better quality.
To answer your question directly. The $10 PWR+ one on eBay is a good one.

Save your Autozone invertor for your coffee maker. I've been down the same road, struggling wih energy demand and production on my boat. Tried both. After many months of experimentation I came to the conclusion the $10 eBay brick and laptop with battery removed is the most efficient method.

If you have big solar array, wind turbine, big battery bank and/or genset it probably does not matter but you will still find the $10 brick more convenient.
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Old 16-11-2013, 15:42   #306
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Re: 12vdc Marine Computers

I've always found the BEP marine DC/DC converters to be excellent. I see they are replacing their range with mastervolt now DC-DC Converters No experience with the Mastervolt product but if you can still find the BEP units grab them.
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Old 16-11-2013, 18:36   #307
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Re: 12vdc Marine Computers

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Originally Posted by noelex 77 View Post
DC to DC converters are nearly always more efficient than using an inverter in the real world.
It depends on a lot of factors, but typically a 30% improvement is seen.

I realise that for the DC to DC converter to step up voltage it goes through an intermediate AC phase, but unlike an inverter the voltage and frequency of this stage instead of being tied to a strict standard like 110 or 240v at 50hz can be selected for the most efficient conversion. in addition the output power is is limited resulting in further efficiency gains.

In general it is worth powering as much as possible on a boat directly from 12v if this is not possible DC to DC converters are much better than inverters at least until the power draw becomes very high.
just a point the vast majority of both step UP and step DOWN dc convertors , from everything from professional DC DC units to cheap wall warts use DC/AC/DC technology , its called switch mode power supply and is available in the smallest integrated ICs.

The primary difference with inverters is that an AC waveform must be constructed at the output. DC DC convertors use simple PWN inductor based conversion on the other hand, resulting in significant efficiencies and good control and regulation.


It is really at tho stage somewhat nonsense to suggest that the best way to power devices is through direct 12v. DC DC convertors are very inefficient and anyway even 12v dc devices will have convertors inside them. It is inefficient to use AC inverters to step up the 12v to 110 and then down to say 18v via a brick, in these cases, a DC DC convertor is way more efficient.

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Old 16-11-2013, 23:05   #308
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Re: 12vdc Marine Computers

The question I put on the table was, if it is possible to connect your laptop directly to the 12v instead going the converter way. I also have a converter aboard and true it is more or less the most inefficient way of getting to 18v or 19v. No matter how good, cheap or expensive the converter might be.
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Old 17-11-2013, 00:05   #309
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Re: 12vdc Marine Computers

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Originally Posted by shanedennis View Post
Save your Autozone invertor for your coffee maker. I've been down the same road, struggling wih energy demand and production on my boat. Tried both. After many months of experimentation I came to the conclusion the $10 eBay brick and laptop with battery removed is the most efficient method.
We came to the same conclusion and halved the power required with a Dell laptop. Phones also charged via a cheap DC > DC charger. The only things left on 240v mains are the dremel and the slow cooker.

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Old 17-11-2013, 00:30   #310
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Re: 12vdc Marine Computers

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I've always found the BEP marine DC/DC converters to be excellent. I see they are replacing their range with mastervolt now DC-DC Converters No experience with the Mastervolt product but if you can still find the BEP units grab them.
It would be handy imo if by using a small programm one could disable/enable the battery
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Old 17-11-2013, 10:52   #311
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Re: 12vdc Marine Computers

Perhaps Nolex or others would like to make some suggestions for good DC-DC converters that are available. Is it really necessary to use Marine standard converters, as they will cost more?

LIND Power Adapter Specialists For Mobile Laptop & Notebook Computing | Lind Electronics makes high quality converters for Laptops and other devices, (milatary ones are way more expensive than the Laptop ones) are there others that should be considered?


For example, with a typical SSB Ham radio that runs on 120v is it possible to reconfigure it by bypassing the 120v plug, to run on DC directly? Some are sensitive to Voltage and if supply drops to 12.2v will not work well. Perhaps some modification for energy savings and DC-DC converter is best way to ensure good power and energy savings? What is entailed?
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Old 17-11-2013, 11:15   #312
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Re: 12vdc Marine Computers

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Originally Posted by rgleason View Post

For example, with a typical SSB Ham radio that runs on 120v is it possible to reconfigure it by bypassing the 120v plug, to run on DC directly? Some are sensitive to Voltage and if supply drops to 12.2v will not work well. Perhaps some modification for energy savings and DC-DC converter is best way to ensure good power and energy savings? What is entailed?
I've never come across a ham radio that doesn't run directly off 12vdc.

I think finding a DC-DC converter that can handle 30 amps would be a bit of a challenge.
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Old 17-11-2013, 11:42   #313
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Re: 12vdc Marine Computers

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I think finding a DC-DC converter that can handle 30 amps would be a bit of a challenge.
Victron has some in that range
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Old 17-11-2013, 18:04   #314
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Re: 12vdc Marine Computers

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Perhaps Nolex or others would like to make some suggestions for good DC-DC converters that are available. Is it really necessary to use Marine standard converters, as they will cost more?
It is not necessary to use a marine standard unit but generally they are better built, and have better RFI suppression built in etc.. If it's needed for Ham radio then RFI is an issue.

Is 30Amps really necessary? I successfully ran my Yeasu 857D off a BEP 20Amp unit for years using it for Sailmail every day. That's a 100W radio so if you want more power than about 200W, say 150W to leave a safe margin, then you'll need more Amps. Remember the antenna is more important than the power that you attempt to transmit.
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Old 18-11-2013, 08:13   #315
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Re: 12vdc Marine Computers

There are 2 open questions here.

1. Is it a good practice to run a laptop directly from a 12 volt outlet? A secondary question - Are all laptops designed to regulate a 12 to 14V input to their desired voltage?

I for one, would't want to risk it without having a backup.

2. Is it a good practice to remove the battery while the power supply is plugged in?

I just tried it with my $150 ST5111. No problems, But I don't want to experiment with my more expensive Dell. One benefit I noticed was there was heat escaping from the battery compartment, meaning the fan will come on less often, saving energy. On the other hand I think it's a little less water resistant.

It should be noted that, with a good battery in place, the higher current draw will lessen as the battery becomes charged. A bad battery might require higher current continuously. I'm guessing that it takes 100-200ma to trickle charge a laptop battery. Anybody know for sure?
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