Leisure battery to power laptop?

Colin24

Colin24

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I am planning to use my laptop as a chart plotter. The software, GPS and charts are all sorted. I intend to go the direct 12 volt from the battery way (rather than utilize an inverter) I vaguely recall reading previous posts about successfully powering a laptop in this way; the only disadvantage being, with only 12 volts available to the laptop –no (laptop) battery charging takes place. I’m not bothered about that.

My questions are these:
1. How long can I expect the laptop, running the chart plotting program to run for on a single 110 Ah leisure battery, roughly, 6 Hours? 12, more?
2. How do I find out how much power (Ah wise) my laptop will use, per hour. If it means anything to anyone the mains adaptor for the laptop has an output of 18.5v – 4.9A – 90W bearing in mind that that is to cope with the demands of charging the battery as well.
3. Is it just a case of cobbling together a lead directly from the battery into the power socket on the laptop? or is some sort of adapter/converter thingy rquired.

Once I find out how to power the laptop from the battery, I guess it’s just a case of endurance, I could always add another 110 Ah battery and would keep a fully charged laptop battery as a standby.
Fore the sake of this example assume there are no other power demands on the battery.

Colin
 
Just been searching through previous posts and have been able to find the answer to the how bit. I need a an appropriate DC to DC adapter to plug into the cigarette type outlet in the boat, also found all sorts of useful links about where to get one.

Main question remains about how long can I expect it to run for on a fully charges 110 Ah battery (with no other demands)
Am I being too simplistic to expect, whatever time it turns out to be, to double if a second similar battery is added?

Colin
 
Well, Im no expert but... very roughly, lets say your laptop averages 100w, with say 20% conversion loss in your dc-dc converter, then you would be consuming 120W from the battery at 12V, this is equal to 10 amps / hour. So if your battery is a deep cycle , you should not want to discharge it more than 50% therefor you have 55Ah available which should give you about 5 1/2 hours. These are only rough figures, but should give you some idea. And putting an identical battery in parralel would double the time.
 
Thanks Paul

Just needed a rough idea, I see from what you say, it’s a case of toting up the watts and dividing by the volts to get the amps. I wouldn’t have known where to start.

If I can up my battery bank to provided about 12 hours worth of power, it’ll be worth my while doing. It’s not life or death, just for my amusement pottering around the estuary.

Best of luck for the ARC
 
Think this might be a bit pessimistic. I had a quick Google at replacement laptop batteries and they are mainly about 3Ah or 4Ah each. If we assume the average laptop battery will give around 4 hours use, this suggests a current drain of the order of 1 amp. So draining a 110 Ah battery to half charge as previously advised, and allowing for inaccuracies and estimating errors, might be expected to give you at least 25 hours use.

I'm no expert, but this feels much more realistic to me. And a laptop never gets as hot as a 100 watt bulb, which suggests its consumption is a lot less.

That's my attempt at a ball park estimate - take it from there!
 
Yourquestion does not really contain enough data to be able to answer with any degree of accuracy. Are all the programmes for the navigation on the hard drive, or will it need to access a CD?
Is the information on position coming from a stand alone GPS that has its own power source, or are you powering via USB?
The 90w power source shows that the laptop is a relatively new machine probably around 2 gig processor. with an 18.5v power source, it is unlikely to run successfully at 12v, and you will also need to check that the DC/DC converter will cope with the power needs
If you are going to run the laptop from the converter, it is a good idea to isolate the battery anyway.

Assuming no usb and no cd drive, I would expect at least 20 hrs from the battery.
 
Sounds about right...

This sounds about right. Bear in mind also that DC-DC converters need at least around 11v, so they won't work once the battery starts to get low. Laptops do tend to use a lot of power.
 
All programs and charts are on the hard drive, no access to the disc required.
GPS has independent power supply (big pile of rechargeable)
Yes the laptop is only 1 year old, but it seems from the links I came up with during my search that there are DC/DC converters for this power range.
I have a separate 110 Ah battery just used for lights and radio. This takes a small charging circuit from the engine 5 Amp
Engine in a Honda outboard.
Depth is an old seafarer with internal battery.

Grateful for your input, does it seem like a runner?
 
Also, would add that intelligent power management on the laptop, eg powering down the two big battery eaters, the screen and hard drive pretty quickly on no use, which is easily done in power setup, makes a huge difference to power consumption.... and then can be re-started in seconds....

I use mine in this manner, through a DC-DC converter and have no power problems... mind you, I do have a wind generator and 2 solar panels.... on a warm day with 10kts of wind, I often end up with excess charge through the dump resistor when away from shore power.... so laptop can't be hitting the batteries that hard....
 
Definitely a runner. Lights will take far more if they are on.

And don't get tied up on whether charts are on CD or hard drive and all that detail stuff. With an appropriate DC-DC converter I'll be amazed if you don't get 25 hrs plus out of your 110Ah battery
 
From Experience, running my Sony 233 old laptop with maplin DC-DC converter C-map ECS and a Garmin 235 Plotter/Sounder, will take well over 2 days to run down
a bank of 2 X 110AH batts.
I know, Ive left them on while out of the water.

Steve.
 
Re: Sounds about right...

While we’re on the subject (sort off)
I’m pretty frugal with my electricity needs, before the lap top idea.
Nav lights on, really not very often at all, about 30 seconds each time I use the boat just to check function. About twice this season I’ve used them due to being late back to the mooring.
Radio, hardly ever, just for half an hour to an hour when passing thru Harwich VTS and for local forecast
Internal lights. Used once or twice but prefer oil lamp or candles, only use the horrible florescent if I’m looking for something.
No power for engine stating (outboard with pull cord)
Depth has own battery
GPS’ all have own battery.

Question, is the little 12v 5Amp charging thing coming from the Honda contributing much? 5 Amps doesn’t sound like a lot. Is it enough to keep my 110 Ah domestic battery topped up.
I don’t have a multi meter so have been unable so far the check anything out.
I’m intending to get one and find out how to use it.
 
Nas

Blummin good point about the power management thing, I had not considered that.

Make sure you keep that Blog of yours going. I love reading about the real world - everyday stuff.
I was down on the dock front late on in the summer (just had a very good meal in one of those refurbished warehouses) and said to SWIMBO "keep your eyes peeled for a boat called Magna Carta" no soon had I said it when I spotted it. Unfortunately there was no sign of anyone around.
 
Go to Maplins, they have just what you need, special 12v (cig socket) to laptop adapter.

You can also see their site on line

* Just seen Frontier's post above, that's what I have, excellent bit of kit /forums/images/graemlins/wink.gif
 
[ QUOTE ]

Make sure you keep that Blog of yours going. I love reading about the real world - everyday stuff.
I was down on the dock front late on in the summer (just had a very good meal in one of those refurbished warehouses) and said to SWIMBO "keep your eyes peeled for a boat called Magna Carta" no soon had I said it when I spotted it. Unfortunately there was no sign of anyone around.

[/ QUOTE ]
Will do!

Keep looking.... and if you see us, shout.... always a cold beer or two on board....
 
If as you say the laptop operates on a 12 volt supply (not 18volt as many do) then you could try simply connecting to your 12 volt battery.
The 13 volts or so when battery is fully charged should not hurt the laptop however it may stop working as the voltage falls to 11v .
Do not use the laptop straight on the battery if the battery is on charge the 14 volts may damage laptop. (you could check to see what voltage the supplied mains adapter provides obviously if it is around 14 volts you will not have a problem) A DC to DC converter is able to take ito account both low and high input voltage but does have an inefficiency such that it may draw 20% + more current that way.
If you need 18 volts you could try another 6 volt (or half a 12v if you can connect to the cell joiners) in series with the laptop supply and the ships 12 volts. This is a pretty clumsy set up for charging but may suit your experimenting.
Good luck olewill
 
I managed for some time with a similar input to my electrics. Even with a lot of engine running, I was always on the edge of running out of power. I also had 2x100 amp/hr batteries for the the domestics. I now have a large solar panel and have no problems.

Suggest you get a panel or accept that you will always have to be charging the battery.
 
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