Solar Panel wiring/charging options

[IslandHops]

I'll be installing 2 panels (130-180w each) on our catamaran (4x 6V house bank). Because it is likely for some portion of one panel will be shaded during different parts of the day, my leaning is to wire these in parallel rather than series. I was planning connecting both panels to a 25amp blue sky MPPT charger and installing thier battery monitor option (as I don't have a Link or any other battery monitoring system).

Over the weekend I was talking with some solar instal companines and one chap suggested that I use 2 smaller charge controlers - one for each pannel - to maximize the benefit from the MPPT "voodoo'
", given that each pannel would have diffferent outputs at diffferent times of the day. My gut feel is that this guy was full of crap and that a single charger would just be reading the combined output of both panels and do fine, but I'm interested in others opinions of a dual charger setup. I could score 2 cheap chargers for less than the blue sky setup, but would still need a monitoring system.

Thanks!

[gbanker]

Go with your gut feeling. IMHO there is no need to make the installation more complicated than necessary. Also, Blue Sky makes quality products, dont know about "cheap chargers". Go with the larget panels you can afford/fit. Can't have too much power.

[scotte]

Originally Posted by IslandHops

My gut feel is that this guy was full of crap

+1 on that. I'll be interested to see how you end up mounting the panels on your Privilege 39, we'll be doing the same next year on ours...

[peterroach]

If you go with two controllers you lose a lot of the magic. Most notable in your configuration:
The MPPT controller takes in a higher voltage from the panels run in series.
You can use smaller wire and lose less in resistance.
If one panel is shaded and the voltage goes less than your battery voltage it will still contribute any AMPS it creates using MPPT and panels in series.

I have an outback power controller and 2 200W panels. Works great. I get @ 45 V when it is running full out. The unit does not stop charging until it is almost dark out. I don't know blue sky but I have heard good things.

[bill good]

I can't see any problems with one regulator & 2 panels in parallel. That will only result in the loss of power from the shaded panel. But I also would like to know what happens when two panels are in series & the same amount of shading occurs. I am about to install 2X 400watt 40v panels & the outback regulator. I am thinking 40v@10A is the safe bet but I am open minded. It is what will give the best result on the overcast day that I am still trying to work out.

Regards Bill

[ess105]

If you have panels with bypass diodes fitted you can run them in series quite happily as long as you're using an mppt to handle the voltage change. As soon as panels are shaded and become resistors, the bypass diodes allow the current from the active cells to flow past resulting only in the overall voltage dropping. I have 4 135W panels wired in series flowing into an outback mppt and it works a dream.