Author Topic: Getting the most out of the solar panels  (Read 2783 times)

woodyunreal

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Getting the most out of the solar panels
« on: October 20, 2013, 05:58:10 PM »
I am trying the get the most current/watts out o my basic solar panels settup. It's a small system about 90 watts. If I do a short across the panels it will do a little above 4 amps Nonload Voltage about 23ish. Ok so here is my question. If i use my MPPT charge controller it will mostly only draw aroun 2 amps http://www.ebay.com/itm/like/200860337132?lpid=82 this the type I'm using. I also have a Grid Tie Inverter connected, this is a similar one http://www.ebay.com/itm/300W-micro-grid-tie-inverter-for-solar-system-MPPT-function-10-5-28VDC-/131024095062 if I run them both only seem to pull 3 amps. So i would think i should be able to draw at least 3.5 amps or better when the charger and the invert are under full load. Any thoughts or ideads. I just hate to be wasting all those amps :) guess it doesnt matter but also the system is running in a 12v configuration . 12v Load like some CF and LED lights.
« Last Edit: October 20, 2013, 06:08:50 PM by woodyunreal »

SeanB

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Re: Getting the most out of the solar panels
« Reply #1 on: October 21, 2013, 12:42:43 AM »
Grid tie inverter will draw maximum power from your panels at all times, remember the current drawn causes the voltage to drop, so using the inverter draws maximum power always from the panels. If you look and measure you will find the power drawn by the grid tie inverter is going to be close to the maximum power rating of the panel if you measure at noon on a sunny day.

woodyunreal

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Re: Getting the most out of the solar panels
« Reply #2 on: October 21, 2013, 06:25:10 PM »
yes that is what i would have thought also, But it doesnt seem to be that way , even with Just the grid tie inverter On it doesnt seem to be drawing the maximum amps, but the Charge controller also by its self doesnt seem to be eather,,,,,,,, and combined they still dont. It just seems like im missing something. i should be able to draw at least close to the rated spec with equipment ,, if im able to get there ratings with a short circuit of a amp meter.

woodyunreal

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Re: Getting the most out of the solar panels
« Reply #3 on: October 24, 2013, 05:16:04 PM »
any one have anyother thoughts :) ?

SeanB

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Re: Getting the most out of the solar panels
« Reply #4 on: October 25, 2013, 12:35:40 AM »
Panel specs are given as 2 points along a slope. One end is voltage with no load and the other is the max current with no voltage. If you look at the power delivered at these 2 points it will be close to zero. In the middle is the MPPT point where the power delivered will be closest to the panel rating of 90W. This will likely be at around 2A and about 15V so. Adding the extra device simply draws more current from the panel, dropping the voltage further.