Quote:
Originally Posted by rotor_wash
Don't forget the value of letting the sun keep your batteries topped off. I mounted mine on the front and use a MPPT controller for a three step temperature monitoring charge. Don't go cheap on the controller even if it is another high priced item on the solar list. It's what makes it work well. I also used Rocky Mtn Ray's mounting idea that used both the Loctite adhesive and 3M VHB tape on alternating mounts. The tape is designed to replace rivets and other fasteners and have some vibration reducing effects.
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I'm not exactly new to solar power. I used solar panels on my yacht for 10 years while living aboard (24/7/365) and sailing around the world. Trust me, I have more real-world experience with solar than most. I didn't use a controller then and I have no intention of using a controller now.
Remember controllers only have the ability to do one thing. That thing is to turn
off the solar panel output when the battery voltage (in some cases, battery temp) reaches a certain point. Controllers do
NOT have the capability of increasing the amount of output from the solar panels. This is a fallacy. In fact, the controller itself uses power to operate, thus being a net loss.
Unfortunately, these panels have a built in diode to keep the batteries from draining back into the solar panels at night. The diode requires nearly .5A of charging current to overcome the "Gate" and allow the panels to charge. This .5A is lost throughout the charging cycle. I personally would rather simply disconnect the panels at night and have that extra .5A of charging throughout the day.
Don't get me wrong, controllers are great if you have a small battery bank or a large solar array or if you just want to leave the panels un-monitored over long periods of non-use of your 12V system. I have none of that. I have a fairly large battery bank (2, Trojan T105 6V golf cart batteries) for 160W of solar panels (160W is a relatively small array) and I doubt very much if my batteries will see 14+V during any one day of camping. I have no intention of leaving the panels hooked up if we leave for days at a time or when in storage.
Controllers are also capable of giving you the optimum "full" charge. However, when I am camping, this is not likely to be an issue because we use our electric a lot.
I have a digital volt meter that I place right at the batteries and it is in plain view. In the unlikely event that I see the battery voltage over 14V, I will simply disconnect the solar array (flick of a switch). If the voltage goes beyond 14.6V for a few hours of un-attention (which is extremely unlikely), that's certainly not going to hurt anything.
Remember, as your batteries increase in voltage they also increase in resistance to the amperage that is put out by the solar panels. The higher the battery voltage, the less amps that the panels can actually deliver to the batteries. For the most part, this is a pretty self-regulating system.......to a point. If the panels are in direct sun (which is seldom on permanently mounted panels) they ~may have the ability to over-charge, fully charged batteries at the peak of the solar panel performance (maybe 1-2 hours a day, if the Sun is passing directly over-head). I will be very happy if these panels simply keep up. I am not at all concerned about over-charging or getting the best capacity charge possible. These are the things that sell controllers. They are simply
not reality. I have nearly 100,000 hours of first hand experience using unregulated solar power. For
ME.......it's a non-issue.