RENEWABLE ENERGY | Off-grid Checklist: ‘Tis the season

Ron Young

Ron Young

By Ron Young —

 

Blooming of the natural world in springtime and early summer brings us back to our outdoor pursuits, which in BC are often in remote locations. If we have the benefit of a seasonal home, a summer cabin, or an RV then chances are some kind of electrical power system is installed. A few years ago these systems were simply a portable generator with an extension cord, but the evolution of that idea has led to quieter, less expensive renewable energy solutions like solar panels and wind generators.

A power system that hasn’t been used for several months needs to be examined carefully to make sure all of the components have survived the elements intact. Following is a list of the basic power system components and suggestions of a few things that you should look at to check their function and integrity.

 

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Solar Panels

Solar panels can be mounted on a roof, on a ground mount, or on a standing pole mount. Over the winter heavy snow accumulation, ice formation, snowmelt, leaf accumulation, and rodents are a few things that can cause potential problems. Examine the wiring for stress damage caused by wind, snow, ice, or wildlife. I’ve seen horses pull connection boxes right off the back of a solar array and rodents and other critters munch on wire insulation. Look at the structure of the mount to make sure wind and temperature variations haven’t loosened bolts or fittings. The ground wire from the panel frame should also be checked. Finally, the surface of the panels should be cleaned with a mild soap cleaner. Accumulated dirt and film on the panel surface can rob you of power and deteriorate the clarity of the glass by etching it over time.

  Tip: If you have an adjustable solar mount, a good strategy on shutting down your seasonal residence is to adjust the panels to their most vertical setting to avoid snow accumulation.

 

Batteries

If the system was left operational over the winter then the batteries should be charged. If you have a battery monitor as part of your inverter or controller then you can see the voltage and a fully charged battery will be around 12.6 volts. Multiply that times two if you have a 24v system or times four for a 48v system. The difference between fully charged and fully discharged is only a few tenths of a volt. A battery at 12.2 volts is below fifty percent charged; in other words, it is discharged.

However, as I have noted in previous articles, battery voltage is a very inaccurate measure of battery health. A high voltage on a battery that drops dramatically when a load is applied indicates a sulphated battery that needs attention. The best way to determine this is by using a battery hydrometer to measure the specific gravity of the electrolyte in the battery. This quick check will tell you instantly what the batteries actual state of charge is.

Any battery that has not had charge/discharge cycles for several weeks or months will need to be equalized. This is accomplished by applying a controlled overcharge for a few hours. This is done through a generator, usually hooked up to your inverter to control the charge voltage or through the charge controller using the sun.

The decision to leave the charging system turned on depends on a few variables. If it’s a small system with just one or two batteries you may want to turn it off and take the batteries home. With more batteries it becomes impractical to do that and the best strategy is usually to leave the charge controller from the solar panels turned on. If the panels receive sun and aren’t covered by snow or disabled in some other manner your batteries will be kept charged, but that’s a big IF. For example, if the solar is disabled or the charge controller fails then you could end up replacing a set of batteries. However, if you have a healthy set of batteries and make sure they are fully charged before you leave for the season (not just topped up) and disconnect all loads then they would not freeze. Even if batteries have become seriously discharged over the winter due to an equipment failure you can usually recover much of their capacity.

  Tip: Put your batteries in an insulated enclosure to help avoid extreme temperatures during the winter.

 

Charge Controller and Inverter

These two electrical components that are the brains of the system are usually located indoors. However, at the very least a visual inspection should be performed to make sure all connections remain secure. A charge controller that is left on will generate a small amount of heat but it can be enough to attract rodents that love to build nests over an ‘electric blanket.’ Both inverter and controller often have fan or vent openings and you’ll want to make sure uninvited guests have not invaded these. If the components were shut down you will want to review the battery charging set points to make sure they are correct. The more sophisticated controllers and inverter monitors have a small battery backup to retain settings but double check to make sure your system is at its optimal settings, which you should have recorded previously.

  Tip: A battery state of charge monitor, which can be purchased separately or incorporated into a charge controller or inverter, can give you a detailed report on several months of charging history. This not only helps troubleshoot problems but also tells you how well the system is performing and if there are any stray loads that you are unaware of.

 

 

Ron Young is a renewable energy professional that designs and sells and installs solar, wind, and micro-hydro systems. He operates the earthRight store in Williams Lake, BC and can be reached at info@solareagle.com.

Copyright Ron Young 2014

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