One more thing. So called 12 volt panels are not 12 volts. The one 12 volt project I have the VOC of the panel is 31 volts and change. Still called a 12 volt panel. The MPP is 28 volts. Series the MPP would be 56volts for two panels. This is shy of 48 volt system requirements three panels would work leaving an extra panel. So the system will produce well in cloudy skys panel MPP would be better at 70 volts or above. Your controller must handle VOC of panel array. Spec sheets for many panels can be found at sun electronics online. Choose before you buy anything.
Kevin
Consider a controller for each batch of panels you purchase. The reason you should do this is one shaded panel will bring down the production of the complete string connected to the controller. This is much the same way a bad battery draws down the bank.
Depending on your view you might consider looking at controllers offered on aliexpress. I have a 60 amp mppt controller that was much less costly. It is over 3 years old now with no problems.
I would recommend panels first then controller. The California gov's solar installation guide sets a spec. For variance between panels that can be a problem should the manufacturer change panel spec between purchases. I let a year pass between panel purchases and found it hard to find matching specs. I wound up selling off my old panels at a loss because it was the best choice financial. To keep the old I would have needed a separate controller that is fine, but shade is not a problem and all new panels was cheaper. For a reference I am running 1150W array. 24V system. The controller is running half capacity. I could double the array but the new array would have a different pitch(angle) and would run better with their own controller.Kevin
On Aug 28, 2016 2:29 PM, "king_of_neworleans" <no_reply@yahoogroups.com> wrote:I have been advised to get my MPPT controller first, and then get solar panels to match it. My goal is to end up with 2kw of solar charging capability, or as near to it as practical. I don't mind starting out with an array of maybe 4 100w 12v panels in series and adding to it as money appears. 400w of solar power is 400w more than I have now.
So I am thinking go initially with a controller that will easily handle all the PVs that I could possibly ever install, rather than start with a small one and upgrade. Just a quick browse on Amazon found this as an example:
Outback Flexmax 80 Amp MPPT Solar Charge Controller $533.00
Outback Flexmax 80 Amp MPPT Solar Charge Controller
I saw some with 40a and 45a ratings at 48v (battery) but they were not much cheaper than this one, and I figure bigger is better in terms of heat dissapation etc. I read the manual and apparently this unit is not very picky about PV array voltage. Output is adjustable, 12v to 60v. Not saying that this unit is the one I am going to get, just using this as an example.
BUT
I have heard of guys using several small controllers instead of one big one, even a mini controller for each panel. Is that a better way to do it, or is a single controller better? Note that I will also have a separate 12v emergency battery, controller, and panel for backup power to bilge pump, VHF, etc. so redundancy is not such a big issue.
Are there any issues I need to be aware of, regarding series/parallel connection of solar panels? If I avoid parallel connections then I would have to resort to multiple charge controllers, right?
I have no mast and boom, nothing to shade the panels, FWIW. They will be mounted on a flat hard canopy covering (and shading) pretty much the entire boat, even hanging aft over the stern if needed. I do not plan on tilting or otherwise directing the panels. I don't think the tradeoff is a good one, for me. I need to keep mounting simple and sturdy.
Keep in mind that for me, money IS an object and I am not interested in absolute best equipment and methods if they cost significantly more. So any comments or recommendations from those with actual solar charging experience are welcome and appreciated.
Posted by: Kevin Pemberton <pembertonkevin@gmail.com>
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