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# match potential emergency energy sources w/ critical equipment Answered

Trying to match potential emergency energy sources (solar, inverters, auto/marine batteries, wind turbines) with particular devices necessary for emergency response planning (laptops, flashlights, refrigerators, handheld radio units, other RF gear, wireless/wired networks)

1. Trying to calculate how much energy and in what form we'd need to, for instance, reliably keep a laptop running during power failure.

2. With respect to devices that need DC power - such as walkie-talkies - which are usually recharged (at least in North America) from AC power, through a DC converter, and then charged:: is it possible with devices which generate DC power - such as solar PV generators - to charge them directly without converting to AC and back to DC?

We're looking not so much for particular matches between power source X and device Y - more methods for making the calculations.

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If this is really critical equipment, then you need professional advice. Consider this along the lines of medical questions.

I think that's an excellent approach. But - with a medical question, you start with a general practitioner, who might refer you to a specialist. One of my collaborators is, in fact, an electrical engineer - his take was that there were so many variables, the best place to look would be in a community - like Instructables - where people have already solved the same or similar problems.

We thought about approaching solar manufactuters - but wanted to start here, because - I hope this makes sense - it's more a practical, "engineering" problem, rather than a more precise "scientific" question.

Do you have a professional in mind? Or a type of professional? Any suggestion much appreciated.

Jon

1. You will need to know how many watts your laptop uses. Watts = Volts * Amps. A laptop will draw approximately 125-250 Watts. You will need an inverter that can handle more watts than your device uses. Look at the inverter's continuous watts and not the peak watts. Watts or volts and amps will be found on the power supply of the laptop.

If you plan on running the inverter from a battery, but not charging the battery faster than it is draining, you will need to calculate battery life here:
http://www.alternate-energy.net/batteryamphours03.html

2. You can charge many devices directly using DC, however inverters are around 90% efficient and are the safest option. For DC, you can buy a universal adapter that converts 12 Volt DC to lower Volt DC. This will not power your laptop as most laptops use 19 Volts. Here is a sample product:
http://www.alternate-energy.net/batteryamphours03.html

You should have the solar panels charge a car battery and run the devices from the battery. A solar panel will not be able to charge the devices directly.
Best of luck.

1. You will need to know how many watts your laptop uses. Watts = Volts * Amps. A laptop will draw approximately 125-250 Watts. You will need an inverter that can handle more watts than your device uses. Look at the inverter's continuous watts and not the peak watts. Watts or volts and amps will be found on the power supply of the laptop.

If you plan on running the inverter from a battery, but not charging the battery faster than it is draining, you will need to calculate battery life here:
http://www.alternate-energy.net/batteryamphours03.html

2. You can charge many devices directly using DC, however inverters are around 90% efficient and are the safest option. For DC, you can buy a universal adapter that converts 12 Volt DC to lower Volt DC. This will not power your laptop as most laptops use 19 Volts. Here is a sample product: