Florence I.T. Computer help business support and consulting for Northampton, MA

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Solar Charging PDF Print E-mail

This page has been setup to support an article published in Green Living Journal on setting up a small, off grid solar electric system for charging gadgets like an iPhone. The article PDF can be downloaded here.   Florence I.T. is not a renewable energy consultant but we've gained some experience setting up our own system that runs this web server. We hope the links (and article notes, below) are useful!

  • The Deep Cycle Battery FAQ from Northern AZ Wind and Sun can be found here. This covers EVERY question you may have about buying, maintaining or testing your solar charged battery bank.

  • Northern AZ Wind & Sun's website is here.  They have a great online store with fair prices, and an excellent user forum with very knowledgeable and helpful members, most aren't even employees.

  • New England Solar Electric's website is here.  They sell everything related to off grid living, from components to complete kits for offgrid cabin or home. They also sell lot's of good offgrid/battery maintenance books. Expert consulting available if you're buying a system, or is available at an hourly charge otherwise.

  • Another local resource is  the Alt-E store. They usually have good prices.

  • If you're looking for super efficient LED lights (either small 12V night lights, or very bright AC household fixtures) I highly recommend the products at superbrightleds.com.  We have posted some test results of the various products we've bought there over the years.

  • Wondering how many hours of sun you can expect in your area? Checkout here.
  • Florence I.T. provides the subscription to Home Power Magazine for Forbes Library.

Tech Notes on the article:

NOTE ** Let’s clarify a few sad facts about solar panel ratings. A 10 watt solar panel will give you on average 7 to 8 watts of power in full sun. It only generates 70-80% of its rated output because PV solar panel power ratings are based on Standard Test Conditions (STC) of 77 degrees, perfect tilt to the sun, and other ideal conditions. Also, a solar panel will output a lot more power in the cold, and much less in very hot weather. If we want to build something that will charge your iPhone properly, our calculations must assume for these losses and be built based on the worst case scenarios, such as short winter days. Why? So you will have the power when you need it, even if it's raining outside for a few days.

** Note if you might want to expand your system in the future ** For my small solar night lighting system, I use the “Xantrex C12” controller. It’s a solar charge controller and a lighting and load controller. Our small night light system uses this controller with a 10W panel to run some LED lights that come on automatically when the sun goes down each night. It works great and can handle more and larger solar panels (up to 12 Amps). It’s about $100 with a 2 year warranty. This controller will also work as the charge controller in you cell phone charging system above, and could function dual duty as a lighting controller and give you more upgrade room for more solar panels.

** Note ** A system of this size system would also be a good small battery charging station. Any of the AA/AAA battery car chargers would also run on a small system like this. An Amazon search of “12v AAA battery charger” brings up a list of items that will work. I charge all of our AA/AAA batteries on a similar system. Just be aware that the extra power usage to charge your AA’s (or another cell phone) may shorten the days of charging you’ll have available for your phone. It also may discharge your solar battery more than should be done, shortening the solar battery's life. In order to avoid this, try charging other small devices on a sunny day while the sun is shining. This is a great way to take advantage of excess power. For example if you charge your equipment while the sun is shining, after your charge controller says the battery is charged, you will use power directly from the solar panel, so battery capacity is not an issue.

I recommend getting a volt meter to measure the battery's voltage. Low cost models can be had for under $10.00. As you may recall we mentioned not letting the battery discharge below 50%. To get the most from your battery investment, you should occasionally measure your battery voltage after you have used your system to charge your devices, at night. Basically your 12V battery should never have a voltage below 12.1V (60% charged, or 40% discharged). With 5-6 days of clouds in the new England winters, it’s possible your system may dip this low. If it does, do not charge anything on the system until it gets a full charge again. Many people report their batteries last FAR longer if you never let them get below 12.45 (25% discharged). Realistically, this means you might have to forgo using the system occasionally from December to February in New England.