Originally Posted by lawrence_craig
I have an MPPT controller. Measured peak voltage is about 15V, 10A.
That’s the thing, I’m getting nowhere close to 300W. I have never seen above 200W. But I have only had during winter in the Caribbean.
Just to clarify, efficiency, in this discussion, is meaningless. If the panels
are rated at 150 Watt each then that's their rating and the only impact of efficiency is in defining the physical dimensions of the panels themselves. So a 30% efficient 150 watt panel will have a smaller surface area than a 25% efficient panel. But both should "theoretically" produce 150 watts in the same "perfect" conditions.
As to total output in reality, like A64, I'd like to see over 200 watts on that combination. My system consists of two banks of 380 watts and I reguarly see 360 watts from each bank in the middle of the day for about 2/3rds of the year, as the boat
swings around in the wind
(the rear pair are shaded by the aft stay so things have to be perfect for them to put out full power, the forward pair are un-shaded if I pull the boom to the side)
To test the panel output you do need to do a few things.
1. You need to know that the battery
bank can ACCEPT the full 300 watts. There's no point testing with the battery
bank full, the regulators will simply reduce the output of the panels to maintain float. In the case of my boat
, when it is totally shut down with no load, that means the front panel combo put out 0 watts and the rear panels produce about 7 watts. If I want to test my system all I have to do is run the coffee machine which sucks around 1400 - 1800 watts. The panels can then put out their full potential
2. You need to angle the panels so that they are perpendicular to the sun in BOTH axes. That's not easy and will probably involve dismounting the panels.
3. The sun needs to be at least reasonably close to equinox in your location. In practice, here in South Australia
, I found in testing that I could get full output from good panels as much as three months either side of the local equinox, which surprised me, but I wasn't complaining. I don't know how low the sun is in the Caribbean in winter so I can't comment there, but it probably is not helping.
4. And, of course, as you probably know, there has to be absolutely NO shading on the panels at all. Regardless of the marketing
crap that came with the panels.