Renewable Energy Questions/Discussion > Automation, Controls, Inverters, MPPT, etc
Battery voltage sensor placement TrisStar 45 MPPT
ChrisOlson:
--- Quote from: rossw on January 26, 2012, 07:06:40 pm ---Tip for you, chris - when you install your weather station sensor, install it close to your solar panels, and most critically - install it facing exactly the same way. That will NOT be the way they tell you to install it, which will be perfectly level. If you want to use it for this purpose, you want to know the sun relative to the panels, not relative to the ground.
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LOL! I was reading the instructions for it as we speak. It says to mount it on a pole in an unshaded area. It shows a picture of it and it's supposed to be at the top of the pole so it doesn't get any shading from the pole during the day.
I'm going to make a bracket and bolt it to one of my solar panel frames at the same angle as the panels.
Yes Rover, I have other sources of power that may affect what the MPPT controllers do. But to me this makes sense to measure the solar power available vs what I'm actually getting. My APRS logger logs to the SD card every 2 seconds. And I have to dump the data into a spreadsheet or MySQL database to graph it or analyze it.
My weather station does the same thing - it logs the raw data to csv, except every second instead of two seconds.
I'm not seeing why I shouldn't be able to compare the two, irregardless of what the bank voltage is or what the rest of the system is doing at the time. If I'm only getting half (or whatever) of the raw kWh over time of what the available solar power and efficiency of the panels says I should get, I got a problem someplace. And that's all I want to determine, really. Is the solar power actually there and I should be getting more power from those panels? Or is the real problem just that the sunlight isn't getting thru because of conditions?
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Chris
rossw:
--- Quote from: ChrisOlson on January 26, 2012, 08:00:10 pm ---LOL! I was reading the instructions for it as we speak.
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Shhh! Don't admit to that, or everyone will think you're a wierdo!
--- Quote ---I'm not seeing why I shouldn't be able to compare the two, irregardless of what the bank voltage is or what the rest of the system is doing at the time. If I'm only getting half (or whatever) of the raw kWh over time of what the available solar power and efficiency of the panels says I should get, I got a problem someplace.
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Rover has a valid point that you're perhaps missing.
Unlike a wind turbine, were you have to keep it tamed - if you're not *USING* the power, you have to *WASTE* it, solar panels are different. If you can't *USE* the power, you simply don't *TAKE* it.
So if your batteries are at a point that the charge controller has moved into "absorb" or "float", it won't be taking all the power your panels *COULD* make, so whatever you're measuring won't be indicative of what you could achieve. It's a fair point, but if you can compare "potential" to "realised" outputs, you will at least get a decent idea of what's what when the panels ARE able to deliver as much as they can to the batteries.
ChrisOlson:
--- Quote from: rossw on January 26, 2012, 08:23:14 pm ---So if your batteries are at a point that the charge controller has moved into "absorb" or "float", it won't be taking all the power your panels *COULD* make, so whatever you're measuring won't be indicative of what you could achieve
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Yes, correct. I know the wind systems can walk all over the solar panels on a good day. If the turbines are putting out 200-250 amps the controllers will have the panels "throttled" back before they even get a chance to do anything. I plan on looking at this data on a day when the turbines can't keep up so the controllers are running the panels at "full throttle". Those are the days when I'm disappointed in their performance.
When the wind is blowing I could care less if I even got those solar panels. But when the wind doesn't blow hard enough to get the bank all the way up, that's why I got them. Several guys have told me that I should be seeing 25-30% from those panels on cloudy days when the bank is trying to get to absorb, and I don't even get close to that.
The only way I'll really know is if I put that sensor in for my weather station so I can measure it. I've pissed and moaned about it since last fall. It's time to do something to see if my pissing and moaning is justified, or if my solar setup has a problem :)
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Chris
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