View Full Version : Remote Solar System Monitoring

Mt Shasta Forest
04-22-2007, 11:28 AM
Greetings Everyone,

I am new to this Basic Stamp system, so I will more than likely be asking odd questions.

I am installing a small solar system at our remote cabin on the slopes of Mt. Shasta in Northern California.· The cabin is located roughly 7 miles from the nearest power line.· So designing a solar system to work to get the most out of the suns energy is our goal.

We are using 4 each 53 watt Solarex Panels, with a Trace/Xantrex C35 controller charger.· Right now we have two Trojan 30H 12 volt batteries with a 20 Hr Rating of 130 Amp Hours.

The problem is with an off the grid solar system, when the battery bank is fully charged and the sun is out your system is basically at idle and all that extra sunlight hitting your solar panels isn't being used.

What I would like to do is to use the Basic Stamp 2 for monitoring the solar panel voltage and battery bank voltage and logging it so I can pull it up later for review.· Then add a couple shunts to measure the current draws and also log them.

The goal will be to take this data and figure out the average amount of power that can be generated for certain times of the year.

Then program the Basic Stamp 2 to monitor the solar panels output and when the batteries are fully charged·and the time of day to control a relay that will shunt the excessive solar energy to a load such as our well pump or run cooling fans in the summer.

I purchased the Full Board of Education Kit with the BS2.

My first hurdle for now seems to be cleared.· I am using an old laptop that I will keep at the cabin.· It is a IBM 600 with a Pentium II running at 266MHZ, with 160MB of Ram, using Windows 98.

I have the laptop talking to the Basic Stamp 2 now.

Last night I plugged in the DS1302 clock and now the great adventure to set it and read it ... then send that to some type of datalogger.

So if anyone has done anything like this i would enjoy hearing about your projects.


04-22-2007, 12:32 PM
Welcome, All of what you mentioned is doable with the stamp. Take a look in the documentation for the Trace and see if you might have a serial output for logging already in the system. Some do.

- Stephen

04-22-2007, 07:10 PM
For some reason I'm having a problem grasping the value of your project. If “extra” energy is available from the solar cells and there is a load to power, wouldn’t it be easier/ cheaper/ simpler to use it to recharge the batteries as energy is drawn from them? What is the value of bypassing the batteries to power the load directly when there is energy available to immediately recharge the batteries?

I can see that monitoring solar energy availability would help optimize the amount of storage available (i.e.; purchasing more battery storage to capture it), but if the available energy is greater than the power required, storage—not source—is the issue.

Perhaps it is your intent to use the extra power for “elective” tasks? Running a pump to fill a cistern for later hydro power generation comes to mind, or warming a thermal reservoir to augment wood heat. I imagine too the value of being able to switch power sources—between hydro, generator, and solar to maximize storage and keep the living space ready for habitation. It would probably be a good idea, as resources allow, to heat (or cool) the cabin when you are not there—to avoid pipes freezing or other unpleasantries. If cellular service is available it may be possible to use a “Pink” module to monitor and control essential systems via the internet. The value of simplification through technology cannot be overstated and I agree with your intent wholeheartedly; I just don’t see the point of your project as I read it.

04-22-2007, 08:45 PM
Did you see the mini solar tracking system in the Completed Projects forum http://forums.parallax.com/showthread.php?p=645192

Mt Shasta Forest
04-24-2007, 02:08 AM
I will look at the mini solar tracking system you mentioned ....
Sounds like that might be an alternative way for a tracker ..
Right now we have the 4 solar panesl mounted on a fixed mount and adjust the elevation ( tilt ) everytime
we go up to the property.
Highest in the sky on June 21st and the lowest on December 21st, a 30 degree swing or about 5 degrees per month.
With it set now at true south and 46 degrees


Mt Shasta Forest
04-24-2007, 02:26 AM
Battery Bank Sizing ....

With solar system the big question is how much power do I need.

With a large battery bank, you would be able to charge it during your peak summer months, but when winter comes, it will take many more days to get the battery bank up to full charged which in cold weather can hurt the batteries.

The cabin is remote, cell phones are hit and miss.· To get a good signal we have to walk about 300 yards to a higher spot to get a connection, and sometimes that isn't good enough.· Within 6 mile so town you get a very useable signal.

Our goal is to find a happy medium .. looking at a worse case scenerio of going up and draining the batteries down to their 50% state of charge in the dead of winter.· Then figuring at least 5 days to full charge them back up .. that of course is assuming clear sunny winter days at the end of December

During the summer, yes we will have the batteried charged in a day or so, then the system wouldn't be doing work.· So our thoughts are at when this happens close a relay and tap that extra solar power to run the well pump, pressurize water system, run a fan in the cabin etc ...

The Trace/Xantrex C35 Control has an RJ-15 jack for the connection of a DVM Panel.· I still haven;t gotten any information back from Xantrex about what type of information is on these pins, anaolog, digital· or ?· This would safe me connections into that part of the solar system.

This weekend I did get the DS1302 clock to work ..... one small step at a time.

Will work on a very basic connection for the Analog to Digital connection, since the LC1298 input range is 0 to 5 vdc I will just use a couple AA batteries to similute an input so I can work out the programing before building the voltage divider.

So any ideas would be greatly appreciated !!