From earlier conversations, I was under the impression I was going to get a big improvement.
From 2 140 watt panels the most I get is about 12 amps, maybe 15. With one panel partly shaded I'm at around 7 amps. Checked with a dc clamp on ammeter. No clouds, sun directly overhead. I checked all wires and connections and everything is solid and wired correctly.
You really need to track day to day averages then see how many Ah's per day you are harvesting, on average or per week on average. 12A seems a bit low but if the panels are hot output goes down. In the South the sun is stronger but the panels get hotter and lose output performance. I have a single 140A panel and routinely see it surpass 8A with MPPT. Daily averages vary with as much as 58Ah per day to as little as 16Ah... With my LFP bank my average MPPT boost is about 18-22%, you should see similar with a 900Ah bank & 280 watts..
The improvements with two controllers can make a
good difference but remember we are talking a 10-15% improvement on a 10-20% MPPT boost. So, when drilled down, money is often better spent adding yet one more panel, if it will fit. If it would not fit, and you have no more room for wattage the the gains can only come from better tracking accuracy or an ability to articulate the panels.... Would I go two controllers on our boat, absolutely, if we had two panels....
Here's what a typical week in spring looks like between PWM and MPPT:
The weather for this testing could not have been worse but it is
real world. I did not stop the testing for rain, fog or clouds because real weather happens and I wanted realistic data. The data is what it is, and simply represents Maine in the spring... Despite the lousy weather MPPT beat PWM every single day.
MPPT Ah's 7 Day Total = 220.44
PWM Ah's 7 Day Total = 182.48
Percentage Gain For MPPT = 20.8% Boost
These were identical 140W Kyocera panels..
