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Power Supply Since we are sailors, power is always a concern. We run our Compaq laptop off a 300-watt Heart inverter. The Heart draws directly from our two 8D batteries. The Heart inverter with computer hooked up seems to draw between 1.5 and 2.5 DC amps. I haven’t been able to figure the variance in amperage draw, but figure it must be correlated with what components within the laptop are running or whether or not the laptop is charging its battery. Our Heart is a modified sine wave inverter. There are three categories of inverters: true sine wave inverters, modified sine wave inverters and square wave inverters. True sine wave inverters are very efficient and produce AC power that is almost indistinguishable from house power. They are also the most expensive type of inverter. Modified sine wave inverters result in greater inefficiency and can cause interference with some devices, although we have had no problem with ours. Square wave inverters are not really recommended for use with computers. Since the processor and other components inside most laptops seem to ultimately run-off DC power, I suspect that converting from DC (ships batteries) to AC (via the inverter) then back to DC (via the adapter on the laptops power supply) is probably not the most efficient route. I have read that converting from AC to DC via a modified sine wave inverter results in at least a 10% power loss. One could guess that re-converting back to DC again probably results in about the same power loss, or about a 20+% total power loss with this setup. To possibly minimize this power loss (and potentially simplify your set up), I would consider omitting the inverter and running straight from your DC power source. Several companies like Targus sell cigarette lighter style power adapters for laptops. Please note I am not an electrical engineer, so do this at your own risk. Power boaters are usually significantly less concerned with power usage. Given the power generating ability on most larger power boats, you usually have the option of running either a desktop or a laptop off an inverter or off an AC generator.
TGW.NET is property of Tim Whelan. All pictures, diagrams and text ©Tim Whelan 1980–2002, all rights reserved. Only permitted images and material may be downloaded from this web site. For usage, please see my copyright notice. | |
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Power supply options.
We use the first option.
DC-->AC-->DC. |
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