Solar Updates


	The testing was going fine in the first few days. I was using both my Apple Powerbook and a portable DVD player, then one afternoon, the power inverter began to beep. I figured this was a low battery power alarm. My suspicions were correct.




		This was what the meter read on the first day of testing. After the power inverter started to beep, I shut off everything and checked the voltage of the battery. The meter then displayed 11.3 volts. As you can see from the chart on the left, the battery was considered to have less than 40% of it’s capacity available. I called the company that markets the battery and I spoke with a really nice and patient guy in their tech support department.

We figured out together that the battery and solar cell combo was not going to work if I had any plans to use a laptop or portable DVD player for any great length of time. Basically the laptop computer was pulling 1.875 Amps per hour from the battery and the solar panel was delivering less than .5 Amps per hour to the battery during the charging process. What it roughly translated into was if I were to use the laptop at night for one hour, it would take about 4-6 hours of charging from the solar panel the next day, to recharge the battery.

The system as it is seen on the Solar Power home page is fine if all one needs is a few hours of light each night. If we were to use LED lamps that use only 3 watts of power, that would convert to a power draw in Amps of .25 amps per hour. What this means to us simple folks, is one hour of use during the night would hardly put a dent in the battery and our little solar panel would quickly recharge the battery the next day. If I wanted to use a laptop computer or a portable DVD player to show instructional videos, I was going to need a bigger solar panel.


	I picked up this Sunsei Solar Charger model SE-1200. The smaller solar panel only delivered 350mA per hour to the battery, so as long as my power draw was less than 350mA per hour, we were going to be all right. To repeat the example above, a 3 watt LED lamp needed only .25mA per hour from the battery and the solar panel could deliver 350mA back to the battery the next day.

If I wanted to operate a laptop computer in the middle of nowhere and I wanted to use it every day for at least an hour, a bigger solar panel would be needed. The fine print on my Powerbook says 1.875mA is the hourly draw it pulls from the battery. This SE-1200 solar panel seen above only delivers 1.2mA per hour to the battery so the laptop is still pulling .675mA per hour more than the Solar Panel can deliver. So to keep things simple, that means for every hour of use, the solar panel will need to charge for 2-3 hours to bring the battery back to 100% charge.

Starting today, June 25, 2007 I will use the Powerbook to do my work for one hour each night and then monitor the time it takes to restore the battery to full charge of 12.6 volts or greater.

Here are the results of my testing so far.

Monday June 25, 2007
At the time I started testing the battery voltage measured 13.7 Volts. This means that it was more than charged up!

I booted up my Apple Powerbook and used it for one hour from 9 PM till 10 PM. At the end of my session I measured the voltage of the battery and it was 12.7. The next morning, the battery was fully charged by 9 AM.

Tuesday June 26, 2007
Staring voltage = 13.1
I turned on a 10 watt lamp and the Powerbook at 9:11 PM and ended the test at 10:10 PM.
The ending voltage was 12.6
The battery was fully charged by 9:30 Am the next morning.

Wed. June 27, 2007
Starting voltage 13.2
8:20 PM, I turned on the 10 watt lamp.
9:00 - 10:00 PM, I was using the Powerbook on the Internet
10:00 PM, turned on a room fan. The 10 watt lamp was still on.
11:03 PM end of test. Battery voltage = 12.2
Again the battery was fully charged by 10:00 AM

Thursday June 28, 2007
1:30 - 3:30, I turned on a 20 watt portable radio.
Starting voltage was 13.0
5:30 - 6:40 PM Turned on the radio again
Starting voltage was 13.0
8:01 PM. Turned on the 10 Watt lamp and a 5 Watt CF lamp. Starting voltage 12.6. The solar panel is still producing power, even though it’s getting dark outside. The solar panel has a feature that will not allow electricity to “reverse” back into itself. This means the solar panel can not kill the battery after the sun goes down.

9:00 PM - turned on the Powerbook and stayed on line till 10:00 PM
10:00 PM - turned off the 10 watt lamp and left the 5 watt lamp on.
11:00 - PM shut down the system for the night.

Friday June 29, 2007
09:30 AM - Voltage meter reads 12.8 volts. Reminder: any reading above 12.6 Volts is considered fully charged.

10:00 AM - Turned on the 20 watt radio. Starting voltage was 12.8.
3:00 PM - The radio has been playing for five hours and the voltage meter reads 12.9.

Here is a photo of the Volt meter and Amp meter that I added to the system. The Volt Meter tells me the condition of the battery and the Amp meter tells me how much power is being pulled from the battery. In this photo, the Amp meter is pointing to 2 Amps, that means the battery will last about 8 hours. This 2 Amp draw is powering an 18 watt desk lamp and my “Boom Box” radio. I bought the meters at my local electronics store and made the Oak wood cubes at home.

Thursday July 5, 2007
7:10 PM- Turned on the two LED lamps and a Desk Lamp drawing 13 watts and the radio. The draw is 2.3 Amps with a starting voltage of 12.8. The radio in the photo draws so little that I think it would take several days of 24/7 operation to kill the battery. The lamp in the photo draws about 1 Amp by itself and at that rate, it would take about 16 hours to kill the battery.

10:30 PM Test ended. 3 hours and 10 minutes. Ending voltage is 11.9. The next morning the battery was at 12.7 volts by 11:00 AM. Anything above 12.6 is considered fully charged.