easun MPPT

[drjaymz]

I don't know if anyone has any experiance with this but my understanding of MPPT is that it will adjust the charging to try to keep the panels producing the most power for a given condition. I have 6 panels with VOC of 220V or something. Given the plate on the panels for optimum output the charge controller should be loading up the panels to somewhere around 180V, and obviously that changes with conditions. I think the algorithm basically adjusts higher or lower and then calculates the power delivered continuosly and so it should always try to maximize P=IV by adjusting V until P is maximal, which sounds complicated but dead easy in the days of microcontrollers.

What I have found recently is that as the day starts it sticks at 120 - 150V all day. I flick the isolator to disconnect the panels at noon and then flick it back on again it settles at 180V and starts pushing andother 10% power. Thats annoying me.

Part of the issue might be down to the fact that my battery is often nearly full so it doesn't end up getting to the optimum / highest current because its already producing more than required. And when you turn the isolator off then when back on briefly there's much more current that can be absorbed by the battery. But its anoying me that I can flick it and cloudy or sun it produces more power.

Maybe someone will know more. I don't there is anything you can really fiddle with for MPPT settings.

There's also one other thing I noticed that coincides. On the panel it shows PV current, when its at 150V it shows 0 but reports correctly over the comms link. After I kicked it and its at 180V then that starts reading correctly like 31A for charging. Thats also annoying me.

There's one thing; accepting when you have cheap hardware that its not going to perform like something thats much more expensive. But its much much more annoying when it shows you what it is capable of doing, but doesn't until you kick it every day. Its like its doing it on purpose.

Sounds like a firmware bug - or not really a bug because it works but not as optimal as it could be. I haven't ever faffed with the firmware version but its not that old so I am assuming its already up to date.

 

[Mattb4]

Which EAsun SCC do you have? If the load is there it should attempt to produce power from the solar panels. The PV voltage dropping to zero during operation sounds like a weak connection somewhere. Yes if your battery is nearly full than the production from the panels drops. Once you enter CV of charging the amperage to maintain CV is less until the SCC decides to either stop charging or run at float voltage.

Some SCC do not have the best MPPT Algo's and will cycle panel input at intervals from max production to near nothing as they seek the latest Impp.

 

[drjaymz]

Its the 3.2KW Hybrid. The voltage doesn't drop to zero except when its night, there isn't a connection issue, if there were at 10A DC then trust me, we'd know about it. It also doesn't cycle it picks a tracking point of around 150V which varies with the lighting conditions as you'd expect. But when I cycle the panels i.e. disconnect and then reconnect it picks a much better tracking point of 180V and produces more power.

That is what is annoying.

If you look at the voltage and current it is tracking. You'd think what it should do is once its over about 120V it should continually increase by a few volts and then measure the product of current and voltage and if its higher increase again until it starts becoming lower. It sort of does but seems to get in to trouble between 150 - 180V. It could be a characteristic of the panels that causes this, they are not as linear as the graphs show. Its a bit tricky because it doesn't know when increaseing the voltage if a drop is because of the load on the panel or if the light output fell, so it has to do it continually.

 

[Mattb4]

Yeah it all sounds like a poorly functioning MPPT part of the SCC. One thing that might help, if you can do it, is to try a different PV Voc level by changing your array's configuration. Of the various SCC I have used through the years there seems to be sweet spots for voltage input that produce better than others.

 

[drjaymz]

Yeah it all sounds like a poorly functioning MPPT part of the SCC. One thing that might help, if you can do it, is to try a different PV Voc level by changing your array's configuration. Of the various SCC I have used through the years there seems to be sweet spots for voltage input that produce better than others.

Yeah, I think that when it sees 200V and works its way down to 180 it works better then on the way up when its bogging it down. A V/I graph for a solar panel looks like a straight line and then flattens off and then winds back to 0. But, in reality is a wiggly line, multiplied by 6 panels it could just be that the jump that the MPPT algorithm makes in voltage may indicate to the algorithm that its already past its peak or the improvement isn't large enough for it to keep going. As you say its a sweet spot. Curiously, when the sun is lower in the sky the shadow of my house passes by this doesn't happen, it goes to 180V as soon as the shadow passees. So I'm sure its something to do with the panel characteristics and the sunrise we're currently getting. They are Trinsolar 265 Panels.
Today I was getting about 980W until I turned the panels off and then I saw 1.34 KW afterwards peaking at 1.45 which is the highest I have seen this year.

 

[drjaymz]

What I will do tomorrow is let it stagnate at 150V and then turn a heavy load on so that I'm consuming at least everything it produces and see if it panics and wakes up without a boot up the backside.