Solar system data

The care and feeding of batteries:

Thanks to my friend Steve Heller, I was alerted to an article about charging batteries in parallel. In the traditional thinking the battery bank is hooked up as a long string of parallel batteries. The article makes the case for a diagonal connection. As the material is copyrighted I shall refer you to the site and you may draw your own conclusions. However, both Steve and I have changed our solar battery load and charging connections to the recommended configuration in the article.

System Data

I have manually taken data for three days as it is the weekend and I am home. The collection timing was not perfect but I tried to take data least every 90 minutes or 60 minutes if I could. I saw the expected bell shaped curve for current that started in the morning with about an amp of charge current at 0800 and then down to about 700 mils by 4:00 pm with a peak of about 6 amps during the period from 10:30 to 2:00pm. The trouble I face is the shade from my neighbors tree in the afternoon.

With the failed panel installed, and facing due west through a break in the neighbors trees, the first day has increased the late afternoon output to about 1.5 amps from 700 Ma and this was on a hazy day. (I do find that once you have a solar system installed, you pay close attention to clouds). Once the PLC is installed and the code finished, I will have real-time data on this page. For the moment I can say that by having the panels oriented the way they are, I am able to get more charge current over a longer period from the system then having them all face the same direction and angle. I have not experimented with putting them all in one direction for a day and taking the data verses the present orientation, but I will do that to satisfy my curiosity that what I have done is the best utilization of the available resources.

Update  5/6/08

I have found that as I continue to use the system, despite doing all I can to optimize it, that I get a little behind each day in replenishing the energy I consume. This makes the strong argument for a wind generator to be added to the system. We have had some storms pass through the area with the consequence that we have had a series of cloudy days. The output from just the solar panels has not been adequate to bring the system back. While I have quite a bit of reserve battery capacity, I can see the trend is down so it is time to push the wind turbine project up the schedule. My immediate solution is to use the AC powered PWM charger to bring the batteries back. While this works, it consumes about 60 watts from the grid to do it.

Update June 19,2008

The days are longer now and because of that, I am able to replenish the batteries with just the solar panels. The wind turbine is ineffective at this moment as we have virtually no wind and what wind there is, does not turn it fast enough to make a difference. I have added the PWM charger to the configuration so that when I get several days of clouds I can replenish the energy I have consumed. While this is far from ideal, until I am able to get additional solar panels and the Vertical axis wind turbine on line, it will have to do.

As a point of interest, the PWM charger consumes about 60 watts per hour of AC but powering the TV and satellite system from the grid consumes about 275 watts per hour. Therefore, using the PWM charger for a couple of hours to augment the solar system is still an energy savings.


Update July15, 2008

Although the solar days are longer at this time of the year, I do not get the full benefit because of shade from my trees and my neighbors trees. However, I find that I am able to keep the batteries charged as long as I have a full day of sun. I do keep a grid tied charger available should I drop below 12.4 VDC. However, I have had to use it only when I got three days of clouds in a row.

Update August 4, 2008

Battery information


Data on solar output:  October 27, 2008



The graph shown above was made using data from late August to late October. As I have yet to finish the software for the monitoring system, I simply took notes as I went past the solar regulator. Some days I took only one reading and others I took several. The typical sunny day showed that I had a solar day from about 10:00 in the morning until about 3:00pm in the afternoon. The solar panels would produce between 2.1 amps to a high of 6.6 amps. Late afternoon was when the sun went behind my neighbors tree and the output would drop off.


The chart was made using an Excel spread sheet so the dates are run together because of the format I choose.


The chart below shows one day in August that I took quite a bit of data on the solar output. It was a cloudy day with a good bit of wind so the shadows created by the clouds are very apparent. I think it is interesting as it shows how dramatically a small shadow can reduce the output of an array. It also shows the need to plan the size of an array to accommodate cloudy days.

Herb & Barbara our interests and family