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Power supply is quite infrequent in the area where I live so I want to create a power backup for my router(rated 9V, 1A). I'm planning to use solar, and possibly wind power. I searched for some solar panels and found some cheap ones rated at 9V, 70mA. How do I use these to create the required output?

Could you please help me with how I would set this up? I asked in the DIY Stackexchange and was sent here.

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    \$\begingroup\$ Look for different panels. You'd need at least 15 or so panels for the router to start plus few more for control electronics. \$\endgroup\$
    – AndrejaKo
    Feb 8 '11 at 19:00
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    \$\begingroup\$ Also, 70mA is the rating at 1kW/m2 incident sunlight. You will only get that at the tropic at the solstice at noon, and even then under the best conditions. You should expect quite a bit less in normal usage. I have no idea where the poster is geographically, but 10% of the rated current is not uncommon. Under realistic condition, the asker is looking at 150 panels. \$\endgroup\$
    – drxzcl
    Feb 21 '11 at 15:01
  • \$\begingroup\$ My previous answer is relevant: electronics.stackexchange.com/questions/83144/… (you will need to put different numbers into the same arithmetic) \$\endgroup\$
    – pjc50
    Nov 3 '13 at 10:57
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I know you've specified that you want to use solar panels, but have you considered using a UPS?

A quick search comes up with a $115 550VA/330W APC UPS which should be adequate to supply a router for a few hours at least, possibly more.

This will also be cheaper than providing the equivalent power in solar panels, be more reliable (doesn't rely on a sunny day), and far easier to set up.

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  • \$\begingroup\$ I concur, 9W worth of solar panels is quite a bit. \$\endgroup\$
    – drxzcl
    Feb 21 '11 at 15:00
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First, you should measure the actual current draw of the router at full load (try transferring a large file). Does it actually use 9v 1A, or is that the rated power supply it came with? You might find that it uses less than 1A. You could also open the router and check to see if it regulates the 9v down to something else. If it uses a common LDO regulator, you might be able to use a lower power supply, or you might be able to replace the regulator with a better one, or remove the regulator and use a supply that matches the regulated power.

In my experience, a Fonera pocket router uses a 5v 2A power supply, but is regulated down to 3.3v with an 1A LDO with a 1.2V drop out, very inefficient. The newer version of that same router uses a switching regulator instead, which solved much of the heat issues. I replaced the regulator in mine with a switching regulator, allowing for efficient battery power operation with little heat issues.

Once you have figured out the minimum voltage you need, and the minimum current you need, you can choose an appropriate sized solar panel (or panels). It will most likely be less than the (9v * 1A) 9 Watts that you originally needed. But keep in mind that solar panel ratings are for full unobstructed sunlight. So a bigger panel would still be "better", despite the size and cost.

The best option is using the solar panel of a decent size, to charge a battery setup, and then run the router off the battery. This way, the amount of sunlight needed would be independent of the actual sunlight available when you need to use the router. And it would allow you to use the router at night.

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Considering the un avoidable losses on the Way , and the variation in supply voltage and current a 12v system with a solar charger regulator and led acid battery would most likely be your easiest and cheapest setup. For the 9v required for your load a dc to dc converter would meet your needs. In addition it can also provide emergency power for other needs. Hope it helps.

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