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Counting Amps & Watts In My Off Grid Solar Powered Home

Living off the grid – with no outside source of electricity – means that you may need to count amps and watts. When solar or wind energy is your only source of electricity then you must watch your energy consumption every day to ensure that you do not drain the battery bank.

Right now I only have two 65 watt solar panels and two 200 AH golf cart batteries. The solar panels are running my LED lights, a laptop, cell phone and some occasional fans. That is all. And the batteries never seem to get fully topped off. It has rained for the better part of three weeks now. That is a good test of a solar energy system’s limits. When the sun does not shine for days on end, you need to have enough reserve energy to get through.

Fortunately the batteries are not getting drained either. I am sort of hanging in there, replacing daily usage without topping off the batteries any higher. Another solar panel will help a lot. I have a Coleman thermoelectric cooler just waiting to be hooked up in the trailer when I have enough solar power to run it. But it takes a full 70 watts full time on its own. I will rig up a homemade thermostat inside it later when I start to use it.

For now, this means no cold food. No cool drinks, no fresh foods, no dairy products. I use powdered milk in my coffee instead of fresh.

I charge my laptop when the battery bank voltage is higher. Normally that means after a long day of sun shining. Actually, contrary to what many people say, solar panels do generate electricity on cloudy days as well. Just not as much.

Living off the grid with just a few small solar panels means watching energy usage closely. I count watts and amps in everything that gets used. For morning shaving a small inverter gets turned on, which powers all of the 120 volt outlets in the trailer. Then after shaving, the inverter gets turned off and unplugged from the power supply. The LED lights use about 1.7 watts each. I use no more than two at any time and shut them off when not needed. The laptop gets closed when I take a short break. The cell phone display gets blacked out. Every single watt counts at the end of the day.

Living fully off the grid is an experience that shows the real numbers in solar energy output. Solar panels are rated at a certain wattage, in full direct sunlight. But normally we only get a few short hours of full direct sunlight each day. That means that a solar panel is only putting out a small fraction of its full capacity most of the time. Tests have shown that, averaged out throughout the day, a solar panel puts out about 65 to 70 percent of its rated capacity.

So a 100 watt solar panel can safely be estimated as providing you with about 70 watts of total energy output during peak daylight hours. You still get some little bit of energy in the mornings and evenings, but not much.

Solar tracking modules and special solar charge controllers can help improve these numbers a little. But these devices are very expensive and not easy to make for the DIY-er.

So until I get that third solar panel up and running, its back to counting my watts and amps.


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Troy Reid

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