Small PV Data Logging

Posted by Jonathan Hunt on April 03, 2008, 01:27:24 PM

Small PV Data Logging
I have a small 47W off-grid PV setup.  I'm using a Doc Wattson DC meter to manually log data about the power generated, peak Voltage & Current, and minimum Voltage.

I'd like to find an inexpensive system that could log this information automatically, ideally shipping it off to a computer so I could monitor it from the web.  I've seen systems designed for larger arrays from Fat Spaniel or others that cost over $1,000.  The cheapest I've found that might meet the needs is from Hobo start at $299 plus sensors.

Has anyone built such a system or know where I could buy one?  I've got a spare laptop around that I could use to host the data once logged.

The things I'm really interested in are:
Vpeak
Ipeak
Vmin
WattHours
AmpHours
V & I at various times throughout the day.


Thanks for any suggestions
 

Posted by James Cormican on April 03, 2008, 01:37:14 PM

Re: Small PV Data Logging (Reply #1)
i think this would work, but compared to the size of the system, it is still relatively expensive

http://store.altenergystore.com/WES-Power-Technologies-Inc/m102/Meters-Communications-Site-Analysis/Meters-Battery-Monitors/Ammeters-Voltmeters-Battery-Monitors/GreenMeter-Hybrid-Energy-Monitor/p3858/

you could also look into a penta metric

james
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Posted by Jonathan Hunt on April 03, 2008, 04:11:41 PM

Re: Small PV Data Logging (Reply #2)
The PentaMetric is definitely more the price I'm looking for and at first glance here:

http://store.altenergystore.com/Meters-Communications-Site-Analysis/Meters-Battery-Monitors/Ammeters-Voltmeters-Battery-Monitors/Bogart-Engineering-PM-5000-U-PentaMetric-Input-Unit/p253/

and

http://store.altenergystore.com/Meters-Communications-Site-Analysis/Meters-Battery-Monitors/Ammeters-Voltmeters-Battery-Monitors/Bogart-Engineering-PM-100-C-PentaMetric-Computer-Interface/p251/

appears to do everything I want.  What is the power source for the input unit?  Does it run off the batteries, have its own batteries or run off an external power supply?

Does the TriMetric

http://store.altenergystore.com/Meters-Communications-Site-Analysis/Meters-Battery-Monitors/Ammeters-Voltmeters-Battery-Monitors/Bogart-Engineering-Tm-2020-Trimetric-Meter-Battery-Monitor/p254/

enable me to offload the data to a computer, or is that why I'd need the PentaMetric?
 

Posted by John D on April 04, 2008, 09:59:07 AM

Re: Small PV Data Logging (Reply #3)
Jonathan;

I use a Lascar USB data logger.  I paid around $70 or $80 for it, and it has only one channel.  It can measure DC voltage up to 30 volts, making it ideal for measuring the output from my panels, or my battery bank.  When I want to measure current I add a shunt resistor (low ohms, high watts) in the circuit, and measure voltage across it.  I simply apply ohms law in order to determine current:  I = e/r.

Try Googling "Lascar Data Logger", or check my blog archives:  http://solarjohn.blogspot.com

I know there are other inexpensive options, including a data logger board for a pc, but I don't have that information handy right now.

Let me know what you decide to do, as I'm interested in an upgrade to the single channel Lascar I currently use.

John
 
 

Posted by Jonathan Hunt on April 04, 2008, 10:59:39 AM

Re: Small PV Data Logging (Reply #4)
Hi John,

I saw your post the other day on the automatic switching for your PV system and thought it was really cool.

How much did the voltage controlled switch, relay and Automatic AC Transfer Switch cost?  Also, did you need to special inverter that can be controlled by the relay or is the relay just in the line from the battery to the inverter?

Two of the Lascar USB data loggers, one for straigh voltage and one with a shunt for current should be able to get me almost everything I want.  Thanks for the suggestion.  Do you know of an easy way to synchronize two of these data loggers?  Is there a button on them to reset the logging that I could press simultaneously?

Thanks
 
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