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post #17 of Old 09-29-2017 Thread Starter
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Re: Custom Built On-board PC / Boatputer Advice

So... just a general FYI reply in case not everyone has thought about this:

Your average PC runs at 80% efficiency - laptops often worse. Your PC uses DC power. So, for example a 200watt usage on your computer will be 240watts of draw. The numbers often get worse at higher power draws. I knew all this before, but was unaware of the next part.

Inverters have similar issues, but beyond that, there is a certain amount of power used to keep the inverter running typically in the 10-25 watt range. And another loss of efficiency in the conversion which very much depends on the size, draw, quality and other factors of your inverter. As an easy rule, I'm told asume 80% efficiency. And my understanding is it's compounding.

Let's say you have a laptop (and you're using an AC brick) pulling 40 watts. It's actually pulling 48. Then an inverter has to take that power from DC and switch to AC so now you're at about 58 watts. That sucks... but here's the really bad part: Your inverter needs a certain amount of power just to run. So, let's say you have a laptop that you swear is only pulling 10 watts at idle. You're now at something like 30% efficiency because your inverter is using say 20 watts + 12watts at best for the laptop. That's 32watts for a 10 watt device due to bad setup! 70% is completely unnecessary if we just bought a DC power adapter for the laptop and left the inverter turned off.
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