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Old 06-06-2012, 13:28   #1
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What is the most efficent way to charge a laptop

We have a 12v system on board, (230 through shore power or the inverter), an inverter and a portable 2.6 kw generator which produces 12v and 230v. We also have solar panels.
When we are anchoring for a long time i need to conserve as much power as possible.
We have three laptops (2 boys aboard).

What is the most efficient way to charge laptops.

I cannot believe using the generator through the inverter is very efficient.

Running the generator to a extension cable and strait to the laptop?

Is it better to get some kind of converter to charge the laptops from 12v sockets.

Any help would be gratefully accepted
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Old 06-06-2012, 13:37   #2
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Re: What is the most efficent way to charge a laptop

I found the 12v car adapter (laptop plugs into 12v outlet) for my netbook. Works like a charm!
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Old 06-06-2012, 14:02   #3
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Re: What is the most efficent way to charge a laptop

I charge my laptop off the AC system via the inverter. There's no doubt this probably uses more power due to efficiency losses of the inverter instead of using a car DC adapter. But it just seems so minor in the total boat power usage to be concerned with. I can run my laptop off its' battery for 1.5 hours and it only takes a couple of DC amps to recharge it.

I would say the most efficient way would be to plug your laptop into the boat power system with a DC adapter during the day when you are getting free power from your panels and run them on the laptop battery after that.
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Old 06-06-2012, 14:12   #4
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Re: What is the most efficent way to charge a laptop

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Originally Posted by Nostrodamus View Post
What is the most efficient way to charge laptops.

I cannot believe using the generator through the inverter is very efficient.

Running the generator to a extension cable and strait to the laptop?
I must not understand the question. Seems to me if you are running your genset which you say produces 230V then that is just passing through your inverter. Your inverter will have an internal transfer switch that trips when it sees genset power or shore power. At that point inverter inefficiency is no longer relevant. The real question to my mind is whether running a genset to power a laptop is efficient and the answer to that is a very loud NO.

Run the laptop directly off 12v if you can find the necessary cables or off a small brick inverter connected to 12v and just run your genset to recharge the batteries would be my advice. But like I said, maybe I don't understand the question very well.
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Old 06-06-2012, 14:44   #5
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Re: What is the most efficent way to charge a laptop

I don't use my central 2500 watt inverter to charge anything. Rather, we keep a couple of small 200 watt inverters that will plug into cigarette lighter outlets. They are far more efficient for that sort of thing.
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Old 06-06-2012, 15:43   #6
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Re: What is the most efficent way to charge a laptop

I fully admit this electricity thing is my weak spot so finding the best way of running various things to conserve as much as possible is a bit trial and error and finding what works and what does not.
The last thing I want to do is run the boat batteries down too much but on the other hand I don't want to restrict the usage of various electrical items if we are making the power.
Working out the best way to use everything to maximise efficiency probably sounds like an interview technique for designing German cars but it is interesting to see what works and what doesn't.
I do like the sound of a small inverter as no doubt it can be used on other small appliances as well.
Thank you for your help and replies.
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Old 06-06-2012, 15:46   #7
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Re: What is the most efficent way to charge a laptop

Using an inverter, even a small one, is the least efficient way to charge your laptop. The DC to DC converter is the most efficient and you can run the laptop off the converter and not run down the battery. There are many sources for these, but here is the source we use . Chuck
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Old 06-06-2012, 17:11   #8
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Re: What is the most efficent way to charge a laptop

Are there not some laptop batteries out there that you can run your laptop off of for 4, 5, or 6 hours? I thought I read that they exist.
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Old 06-06-2012, 17:19   #9
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Re: What is the most efficent way to charge a laptop

You can buy bigger capacity laptop batteries online.I keep a couple of charged spares on hand for emergencies.
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Old 06-06-2012, 19:40   #10
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Re: What is the most efficent way to charge a laptop

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Originally Posted by Nostrodamus View Post
(...) Is it better to get some kind of converter to charge the laptops from 12v sockets. (...)
You can get a car adapter for laptops. They happen to break down unexpectedly so get a quality one.

I am not sure it is more efficient though. One would need to run side by side tests.

We charge of a small inverter plugged into our 12V. We plug regular laptop chargers into it.

b.
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Old 06-06-2012, 20:32   #11
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Re: What is the most efficent way to charge a laptop

I have both a 12v and 120v chargers for my netbook. My 12V charger is 60% efficient using 50 watts to make 30 watts,converting the 12 to 19 volts. It runs rather hot and I can see it loading the house batteries more then using the 120V adaptor with the inverter. The heat produced by the 120V adaptor is much less, runs oh 85 degrees ish while the 12V adapter get hot, about 110 degrees sometimes.

I think the 12V adapter would work better with a car with a constant 13-13.5 volts to it. It stops working about when the battery voltage drops to 12.4 volts or so. I've stopped using the 12V adapter, as it runs hot and pulls more load on the batteries then the 120V with the inverter.
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Old 06-06-2012, 21:22   #12
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Re: What is the most efficent way to charge a laptop

It seems to me that I read on eight other news group that you could put 12 V DC directly into your laptop charger plug and the laptop will run just fine. It will not charge its internal battery but will function. I have not found a plug for my laptop yet to try it. It does seem reasonable as a laptop battery in my Dell, is 11 .something volts (I don’t remember exactly what). I did ask at one repair shop and their response was that they didn’t see any reason it wouldn’t work or would hurt the laptop. Just my two cents, Mike.
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Old 07-06-2012, 01:09   #13
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Re: What is the most efficent way to charge a laptop

Don't run the generator just for the small laptop demand.
Use a small inverter from the boat batteries, or better still a 12v dc to dc converter. The dc converters are usually about 30 % more efficient than an inverter.
Keep the laptop fully charged ( or remove the batteries) for maximum efficiency. Don't forget the laptops settings to reduce power and if shopping for a new one consider if you can do some of the work with a low powered computer. A netbook will only use about 1.2A. Tablets are even better.
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Old 07-06-2012, 01:18   #14
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Re: What is the most efficent way to charge a laptop

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or better still a 12v dc to dc converter. The dc converters are usually about 30 % more efficient than an inverter.
Absolutely, it was a bit difficult to measure because the readings kept flutuating, but using 12v > 240v > 19v to run the Dell laptop took about 4 amps per hour. Switching to 12v > 19v (DC to DC) resulted in a drop to 2 amps per hour.

On its own this isn't very much, but multiply it up for an evenings surfing Cruisers Forum and if the wifey is also using her laptop then this does mount up.

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Old 07-06-2012, 01:18   #15
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Re: What is the most efficent way to charge a laptop

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Originally Posted by sailorchic34 View Post
I have both a 12v and 120v chargers for my netbook. My 12V charger is 60% efficient using 50 watts to make 30 watts,converting the 12 to 19 volts. It runs rather hot and I can see it loading the house batteries more then using the 120V adaptor with the inverter. The heat produced by the 120V adaptor is much less, runs oh 85 degrees ish while the 12V adapter get hot, about 110 degrees sometimes.

I think the 12V adapter would work better with a car with a constant 13-13.5 volts to it. It stops working about when the battery voltage drops to 12.4 volts or so. I've stopped using the 12V adapter, as it runs hot and pulls more load on the batteries then the 120V with the inverter.
Check the voltage at the cig plug socket with the laptop running. A lot of these are wired with thin gauge wire and the voltage may be dropping very low. Not running the laptop and charging the computer t the same time will help reduce he power draw and will keep the voltage higher.
Normally dc to dc converters are more effecient
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