Hi, not sure best approach, so looking for suggestions!
I currently have a single 80 watt panel hooked up to a Specialty Concepts Mark 22 solar controller (max array voltage 26V, max charging current 22A), 4x T125 6v batteries, total of 480 AH cap.
This is sufficient to help extend our dry camping stays, but we still need to run the genny to fully charge every few days.
In most situations I'd like to avoid bringing the genny, and since panels are much cheaper now than the one I first bought, I'm looking to add another panel.
We're not super heavy consumers on the battery (rarely use the furnace, LED lights, couple of hrs of TV at night), but I like being topped up and not having to worry.
I'm looking to add maybe another 130 - 180w panel (depending on price). I assume I need to wire this in parallel to the existing panel. I already wired from the first panel to the controller assuming max amperage and the run is not long (4 ft), so that's not an issue.
Anything I need to consider otherwise?
Thanks
Jayco 2008 26L behind a 2005 'Burb out of the Great White North, eh!
1 DW, 1 DD, 1 DS, 1 SD (shedding dog)
4 x T125's, 300W solar, Yamaha 2000IS
If you want to eliminate generator use I'd lean towards 150 watts per 100 amp-hours of storage. The minimum number of watts to be able to equalize that size bank is 60 watts per 100 amp-hours or in your case 288 watts.
Your looking at new panels
Try to match working voltage "vmp" and open circuit voltsge "voc"
The output wattage does not have to match
Voltage should be as close as possible
Options, always have options, and the journey goes much smoother ....
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I paid $429 for a 120 watt panel back in 1999. Anyone remember what you where making back in 1999? So compared to todays dollars per hour, think that you might have had to work 25% more hours to make $429 for each of those panels, and now they are more powerful and lower cost as well!
End of edit.
You basically want to match the replacement solar panel with the old one in output voltage, and have these be within 1 volt of each other. Or you can count the cells, and match them up that way if you do not know the rated output voltage of your existing solar panel. 39 cells is pretty standard, and has a specific wattage output. Some older panels might have used 36 cells.
I would run a new #10 wire from your 130 - 225 watt solar panel to the controller. I would make the mounts by cutting 6" long 2" angle aluminum from Home Depot, drill 3 holes in the roof side 3/16" and one hole 5/16" in the side going into the panel via a 1/4" bolt and nut.
I would recommend looking for a 12 volt (nominal) panel from this place, you might have to call them and ask what 12 volt panels they have right now.
SunElec.com The actual output voltage is something between 18.6 and 21.6 volts, and it is considered 12 volt nominal. 24 volts are double that output, while anything about 50 volts would be used with a string type controller or house grid tied inverter, sometimes they use up to 600 volts input to the inverter!
I would not go over 200 watts per panel, because the size becomes a issue, and with only 4 mounts, I would not want it becoming a sail up on the roof. My 120 watt panels are about 40" square, and it was difficult to find a good location for them on the 30' RV, with all the roof vents, and TV antenna up front, and the existing panels in the back. I ended up placing them near the TV antenna, that usually will cast a small shadow on the panels.
Fred.
* This post was
edited 05/30/12 02:59am by Golden_HVAC *
The Sun panel is a good price but it is also large at 65" x 38" without adding in the space needed for the mounting brackets. OK for a large MH or TT but too large for many campers.
If you stay in one location for multiple days at a time then a kit to tilt the panels will increase their output watts by at least 50% which is like getting a third panel almost for free (depending upon the tilt setup installed). As little as a 15 degree tilt is all that is needed to see a 50% gain.
wintersun wrote: If you stay in one location for multiple days at a time then a kit to tilt the panels will increase their output watts by at least 50%
This depends on where and when. For most of the US in summer tilted panel will show less than 30% increase, and on some months tilted panel will be LESS productive than flat. You may check this calculator - just use solar radiation numbers in the 1st column, they are not panel-specific. For example, in San Diego for tilted South-oriented panel, 15 degrees tilt in December will result in 33% increase compared to flat panel, in July - no difference from flat. In the same location 34 degrees tilt in December will result in 63% increase, in July - 9% DECREASE.
Not that I have anything against the tilt. For a seasonal site or long stay it makes a lot of sense. For a short stay in spring - depends on how much you are willing to climb the roof. In midsummer - it doesn't change anything.
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