Laptop power on board

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Dave_Rolfe

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I have a Toshiba Equium M50-164 that I want to use onboard without using an inverter. Maplins do a suitable converter from 12v to the 15v that I need but in the blurb advertising it it states that I must be sure the central pin of the laptop power input is positive. How can I test to check this as I have been unable to find out from any other source.

If I take the existing mains transformer and plug it into the mains then put the red probe from a multimeter in the centre of the plug with the black lead against the metal outside of the plug I get a reading of +15.29 v. If I reverse the probes I get a -15.29v. Does this tell me the centre pin would be positive please.

As you can tell my understanding of electrical matters is somewhat limited, I just want to be sure.
 
Might be stating the obvious but a lot of transformers have a diagram of the plug printed on them.

Most have the + on the internal part of the plug to protect from shorts.

W.
 
Most have the + on the internal part of the plug to protect from shorts

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Unfortunately there are exceptions so do not always assume the tip is positive.
 
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I have a Toshiba Equium M50-164 that I want to use onboard without using an inverter.

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Why should you want that? An inverter is an invaluable protection from voltage spikes you will get on your supply.
 
i have seen a few of these melt when plugged in the the 12v system you would be surprised at the amps that some laptops use. but to answer your original question make sure the red and black leads from the meter are plugged in to thier respective posative and negative posts. then what you have said is correct
 
Why not wire in a cigar lighter socket into your boat? The wiring is really simple, +ve to the center and neutral to the outer cylinder terminal and then you can plug in a dedicated in car charger. You could put an inline fuse of 10amp capacity and then use any in-car accessory.

An inverter would allow you to use different mains voltage appliances depending on the power output of the inverter. Unless using for just a few minutes, always have your engine running whilst using aan inverter as they draw a lot of power from your batteries.
 
On a similar vein I have a portable dab radio which runs of rechargable batteries with a built in charger in the radio.The output of the mains adaptor is 12v 5.6a 6va. Can I just wire this up to the 12v supply on the boat or do I need some sort of regulator to stabilise the voltage when the engine is running?
 
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An inverter would allow you to use different mains voltage appliances depending on the power output of the inverter. Unless using for just a few minutes, always have your engine running whilst using aan inverter as they draw a lot of power from your batteries.

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An inverter itself uses only an infinitesimal amount of power - it's current draw is dependent on the secondary consumption, which will be the same whatever power input you use to it. Most have (or should have) a cooling fan and this may continue to draw current when the secondary device is turned off so it is always good practice to switch off the inverter when not needed.

The rated power of an inverter must exceed the total surge power of all appliances that may be connected simultaneously. For a computer that typically runs at 100W it would be be sensible to consider an inverter of at least 120W. Any normal, properly charged boat battery can easily supply the consumption, of usually less than 5 Amps, for a considerable time without running the engine.
 
So what type of inverter are you advocationg? I have both old and new types on the boat and after 12 years experience of them would tend to disagree with the 20watt allowance you advise as this barely covers losses let alone the start up pulse power required.
 
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I have both old and new types on the boat and after 12 years experience of them would tend to disagree with the 20watt allowance you advise as this barely covers losses let alone the start up pulse power required.

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No inverter should have "loses" of 20% and I would not expect the typical laptop to exceed that value on startup. This is splitting hairs, the principle of allowing some leeway is obvious. I personally would certainly use an inverter with a rating well in excess of whatever appliance I would connect to it. In fact, here is my 300W inverter (blue device) driving my Dell Inspiron with plenty of reserve for typical requirements.

Charttable.jpg


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So what type of inverter are you advocationg?

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Not knowing what you wish to run from an inverter I cannot advocate one for your application, nor would I know what is available in the UK - only you can assess that. A genuine sine wave converter would be best but unnecessary for most applications. It is always a good principle to plan for at least double what you think you need.
 
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after 12 years experience of them would tend to disagree with the 20watt allowance you advise as this barely covers losses let alone the start up pulse power required.

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I really had to refute this and did a quick google for modified sine wave inverters, the most suitable on a cost/benefit basis for running a lap top PC on board, just to check for specifications. I found typical values here and extract details of the smallest unit as follows:

Output Power Continuous: 150W
Output Power Surge: 450W
Standby Current: < 300mA
Input Voltage: 10 - 15VDC
Output Wave Form: Modified Sine Wave
Efficiency: > 90%

Note the standard ability to handle output surge power by being 3 times the continuous power component and the efficiency being greater than 90%, resulting in a typical 100W requirement on the secondary needing only a worst case input of ca. 110W to the inverter.

Note also the standby current when no secondary drain is present, it is 0.3A, which is negligible.

Hope this helps you to get your facts straight.
 
I only state what is in the handbook of one of my inverters, hence asking you which type you are using. Not a question of getting my facts right!!
Sounds to me as though you would be lost without Google, but your last statement was just for laptop use where as in previous posts you mentioned using other equipment.
 
I think if you look back over the years you'll find that Willow36 had articles printed and endorsed in all the popular mags re computers on board. If I remember correctly he had a desktop type PC first of all as laptops were not as reliable as now, and this was built in under the chart table with a Philips flat screen monitor hinged down from the wheelhouse roof. Pehaps it's time for you both to back off a bit.
 
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Sounds to me as though you would be lost without Google

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/forums/images/graemlins/confused.gif As my boat with inverter and its data sheet are 700km from where I am writing I needed to obtain some representative figures to substantiate what I knew from my student days, which were a couple of lifetimes ago. So naturally I resorted to the web to find them - don't we all?

It would be interesting if you too had quoted some figures from your inverter handbook to understand why you are advising others that inverters "draw a lot of power from your batteries" when, in fact, they typically have very little overhead above that drawn by the device plugged into them, which really dictates what is drawn from a battery.

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your last statement was just for laptop use where as in previous posts you mentioned using other equipment.

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Laptop use was the thread subject and I therefore chose such as an example. I was concerned that the OP was not put off using an inverter as I personally believe that they are a good way to drive a PC on board, despite the apparent inelegance of converting 12V DC to 220V AC then back to a low voltage DC again. Some computers can be sensitive to voltage spikes, such as can occur to a yacht's DC circuit when the engine is started and an inverter plus the computer's power brick are good isolators in such cases.
 
hi
having used inverters for years on boats, dont belive the jargon crap,you will need an inverter rated at least twice the power you need to last 3-5 years service,as heat build up an a hot summers day kills them in no time at all,
ps: i use inverters from 3.8 kw to 300 w on board for the laptop i use the 300 watt wirered in to a socket as i find cigar sockets over heat on the center pin in time,
 
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