by admin | Jan 25, 2014 | Tech Updates
Finally, after a few weeks without sunshine, the weather cleared up and the sun was shining brightly and the batteries on my solar energy system finally got some serious charge, reaching close to full charge by Friday afternoon. It was also the ideal time to take current measurements and figure out what should be expected of a solar energy system in different weather conditions. For optimal energy production, a solar panel should be inclined about 30 degrees facing south. The panel I used is installed on a roof deck tent structure which is currently not an ideal position for a solar panel. It is facing east more than it is facing south, thus, solar energy production is highest between 10AM to 12NN and would start to decrease by 1PM. That means I should soon modify the roof deck structure so that the panels are in the ideal position. I took various measurements of the current going into the batteries when the clouds cover is very thick, when there is just a thin layer of clouds and when the sun is fully out. This week, I was taking measurements between 10AM to 12NN so I can compare the results for various cloud coverage. When tropical depression Agaton was still in full swing, cloud cover was very thick and the sun was never out. In a previous issue, I measured about 0.4 to 0.7A at about 4PM. I measured between 0.6A to 1.1A between 10AM to 12NN. Last Thursday and Friday, the cloud cover was such that the sun would be fully out for a few minutes then get covered again....
by admin | Jan 18, 2014 | Tech Updates
The sun hasn’t been out for almost two weeks now and my batteries are still not fully charged even if it has been charging for a week after I drained it last week. I now must find out why it is taking so long to recharge in cloudy conditions. In theory, my 100W, 24V solar panel should produce 4.1A of charging current during sunny conditions. 4.1A should fully charge my 100AH, 24V battery setup in 24 hours of sunshine which should be just 2 to 3 days. But because of the the low pressure area (and now a tropical depression), the weather has been cloudy for almost two weeks now. So how much charging is being done in cloudy conditions? Because I don’t have a battery monitor yet, I just created a make-shift shunt resistor. It is basically a resistor with very low resistance and high current capacity. The smallest resistor I could find was a 0.22ohm, 5W resistor. To measure current, I simply need to get the voltage through a known resistor value and use the equation: I = V/R. I also don’t want to introduce a large voltage drop between the batteries and the charge controller and inverter because it would affect charging. I expect to measure about 5A of current and the voltage drop would be V = IR or 5 * 0.22 = 1.1V. This is actually too large. The solution is to connect several resistors in parallel which reduces the resistance. I soldered together eight 0.22 resistors in parallel to get a combined resistance of 27.5mOhm. The voltage drop of 5A across it would...
by admin | Jan 11, 2014 | Tech Updates
By: Jerome Auza Last week was a very good opportunity to test my small solar energy system and how it would fare in cloudy weather providing power for two computers. I started with fully charged batteries on Monday connected to a 600 watt pure sine wave inverter and two laptops with 65 watts and 85 watts power supplies. I guessed that the two laptops will only consume half of their rated power consumption during use between 9AM to 6PM and would be on standby during the night and therefore consume little power. The 100W solar panel should be enough to power them during the day and keep the batteries charged assuming the panel gets enough sunlight. But it was cloudy and rainy most of the week. The setup worked fine until Friday morning when the inverter shut down due to low battery voltage. At 9AM, I can see that the batteries have charged up a bit so I turned on the inverter and plugged the 85W laptop only. By noon, the inverter shut down again which means the power generated by the panels is not enough to power the laptop and the inverter, thus draining the batteries. The weather was still very cloudy. I let the batteries charge until Saturday without any load but by 5PM Saturday, the battery is still considered less than 40% charged based on the indicators of the solar charge controller. The weather, was still cloudy most of Saturday. This got me into thinking that I should be able to see if my setup is charging or discharging the batteries when a load is applied....
