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Topic: Evaluating your solar capacity... (Read 173 times) previous topic - next topic
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Evaluating your solar capacity...
After sizing and installing a solar array to keep in step with usage, it is useful to know how successful your system is, particularly in those months with fewer sunny hours available. Here is a technique for determining available solar performance, using a battery monitor.

Start by bringing the batteries up to full charge, e.g. using the converter, then disconnect shorepower.

At the particular time of day and season of interest, with full solar exposure on the panels (no shadowing), begin.Turn off all easily accessible 12V draws, including the fridge, then check and note the battery charge current - call this 'X'. Next, successively turn on electrical draws, such as lights and fans (but NOT the fridge), until the monitor first shows a charge on the batteries less than 'X', or even negative. Then turn off low-draw fixtures just until the current is about 'X'. Record exactly which 12V draws are on, then turn them all off. You can then reconnect shorepower, turn the fridge back on, or whatever you need.

After dark, disconnect shorepower and fridge, and note there is a negative current on the battery monitor. This is the phantom load on the batteries due to converter circuitry, propane monitor, etc, which is always present. Next turn on exactly those fixtures you recorded, and note the current draw from the batteries shown on the monitor. Add in 'X', and you have approximately the solar current available at that time of day and season of interest.

This will NOT work if your solar capacity exceeds your total demand at the time you are doing the first part, i.e. if with EVERYTHING on,'X' does not change. However, for most of us, the season of interest would be in late or early season when the sun is low in the sky, and this will likely work then.

Steve
2004 FL
2013 Honda Fit
Re: Evaluating your solar capacity...
Reply #1 –
In southern Arizona this time of year, when I tilt my panels, I get about a 30% gain.
That is significant and worth the hassle to do.
Jota
96 23.5 FL
 
Re: Evaluating your solar capacity...
Reply #2 –
Quote from: Jota  - 
In southern Arizona this time of year, when I tilt my panels, I get about a 30% gain.
That is significant and worth the hassle to do.

For those who have no desire to go on top of the roof, adding another panel or two will eliminate the hassle and and possible danger of tilting the panels.
Falling off is no joke.
BTW, tilted panels are only efficient if the rig is parked directly in an east-west direction, get it off by 10-15 degrees and the advantages are lost.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze