Small PV Data Logging

9 Posts
Apr 3, 2008 01:27 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
 
578 Posts
Apr 3, 2008 01:37 pm
Re: Small PV Data Logging

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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9 Posts
Apr 3, 2008 04:11 pm
Re: Small PV Data Logging

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?
 
184 Posts
Apr 4, 2008 09:59 am
Re: Small PV Data Logging

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
 
 
9 Posts
Apr 4, 2008 10:59 am
Re: Small PV Data Logging

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
 
184 Posts
Apr 4, 2008 03:08 pm
Re: Small PV Data Logging

Hi Jonathan;

I use a Morningstar Relay Driver, which is actually 4-voltage controlled switches.  I could have gotten by cheaper, but I wanted to be able to expand later.  The relay driver costs about $150.00.

The relay is nothing special.  For ease of hookup, choose one that has a coil rating that is the same as your battery bank, 12 volts dc for example.  You could even use a solid state relay if you so choose.  I use the relay contacts to turn on/off my inverter, so the relay doesn't need to pass a large amount of current.  In other words, the off/on relay does not pass the potentially high dc input current of the inverter.  (I hope you understand what I'm trying to say).

The automatic transfer switch is made by Iota.  It's rated at 30 amps, and it set me back about $55.00.  Actually, it's nothing more than a relay. 

My inverter has remote on/off capabilities, or in other words, a terminal block.  This terminal block allows me to wire in a remote on/off switch, or in my case, the relay contacts.

The lascar data loggers are programmed via a PC, and use the time/date information from the PC.  If you're setting up two of the lascar data loggers from the same PC, the time/date information for both of them should be farly close.  You'll set the sample intervals, (1 minute, 5 minutes, 30 minutes, etc.), and they should be fairly closely synchronized.  There is no way that I know of to actually connect the two data loggers together for exact synchronization, and there are no buttons or switches on the data loggers. 

John
 
May 8, 2008 12:20 am
Re: Small PV Data Logging

Not sure what type of charge controller you have, but you could upgrade to a charge controller that supports data logging to a PC. 

The best cheapest option I have found so far is the Morningstar SUNSAVER MPPT controller for $244.  It requires an optional PC interface that can't be expensive since it's just a RJ-11 to Serial adapter (Which I can't find anywhere for sale..  Alt-E staff... are you going to carry this??)

I have read the documentation, but I'm still not clear of every parameter it logs though...

Morningstar has a free download of their software that interfaces with the controller (MSView):
http://support.morningstarcorp.com/item.cfm?ItemId=8

Controller link:
http://store.altenergystore.com/Charge-Controllers/Solar-Charge-Controllers/MPPT-Solar-Charge-Controllers/Morningstar-MPPT-Charge-Controllers/Morningstar-Sunsaver-MPPT-Charge-Controller/p6185/


If your looking for something less expensive, The Morningstar TRISTAR-45 is $147.  It is non-MPPT, but offers data logging to a PC.

http://store.altenergystore.com/Charge-Controllers/Solar-Charge-Controllers/Pwm-Type-Solar-Charge-Contollers/Morningstar-Charge-Controllers-Pwm/Morningstar-Tristar-45-45A-Chg-Ctlr-Without-Display/p806/
 

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