Suboptimal tracking in SOLAR mode

[JerryB]

As a new user, I'm gradually getting to know the Classic 150 that I have on my boat (Purchased about January of 2012). The configuration is 9, 240 watt panels (ET solar) wired in a 90 volt string, feeding a 12 volt, 1200 AH bank. Based on only about 10 days of observation under various sunlight conditions, I have observed that the SOLAR mode often assumes an operating point that is obviously suboptimal. For example, the array is putting out about 3-400 watts under overcast conditions and the controller suddenly drops the input PV voltage to slightly above battery level with output dropping to 30 watts and it sits there despite no change in sunlight (as measured by a pyrometer). After quite a while it starts to correct and a few sweeps later finds the original operating point. Using the %VOC function will restore the full output, but I would assume the SOLAR mode should do a better job, no?

Another, possibly related behavior, occurs in early morning. Starting at the resting condition, the controller wakes up and adjusts to an output of 100 watts or so for a few seconds and then reverts to resting. This behavior repeats until (my impression at least) the available power climbs past a few hundred watts. Again, using the %VOC mode results in expected behavior. I have tried setting the "forced sweep" parameter between 15 and 1 minute, with the shorter time working better.

When the Classic works, it works beautifully, but I'm wondering if I'm doing something wrong to trigger what seems like abberant behavior. Any suggestions?

Jerry

[boB]

Hi Jerry.  We will have a look here at MidNite with a 12V battery and similar array to see if we find the
same thing.  Unless you have significant partial shading, this should not be happening.  At least it
shouldn't happen this much.

I think we can make this better.  How old is that Classic ?  Can you look at the firmware revision or
date in the information screen ??  Just press the STATUS button a few times until that info comes up.
If it is a real old classic, you may have to press the RIGHT ARROW key a few times instead of the
status key itself to get to that screen.  That method was fairly short lived in software though.

Thanks,
boB

[dapdan]

Jerry B,

I don't think you are doing anything wrong because I get the same issue and I have been using my classics for about a year. I had informed midnite about this in another thread and it still happens and operation in that "Solar mode" has not been resolved. What I have done is change the operating mode to " Dynamic mode" until midnite figures it out. I have upgrade to latest firmware on one of my classic (April 1) and it still happens. I don't think if the hardware(assumption) because I have three classics and I don't think is goegraphical location as you are having the same issuew I have/had. As I said I have resolved it temporarily by operating the classic in dynamic mode.

Cheers...
Damani

[dapdan]

Jerry B,

Here is a link to my post w.r.t to our similar issue:

http://midnitesolar.com/smf_forum/index.php?topic=364.0

Maybe others are having this same issue but don' t know it because for me it only happened in certain times of the day and not all of the time and you have to be watching the output all of the time to see it happen or you will miss it. So because I have the local application and it is always in front of me when I am on the computer (which is at least 50% of the day) I see when it happens. However most persons might not enjoy watching the calssic harvest as much as I do so they would not notice it and there is not logs or history showing that it has occured you have to be watching it for a couple of hours to see it happen.

Cheers...
Damani

[Halfcrazy]

Damani and Jerry

Do you guys have the serial #'s of the Classics in question? We just have not seen or been able to re create this? Is there something that is happening IE clouds or a full battery that is causing the Classic to drop in power and then the Sun comes back and it is not tracking correctly?

In Solar mode did you alter the Sweep Interval? In theory if the Classic is in Bulk MPPT it should never get stuck but if it did for whatever reason it should correct itself upon the next seep.

I will let boB chime in here as well but My observations and understanding is that the Classic will basically stay on once it can maintain ~15 watts output to the battery. When you here it Clicking on and off at or around 100 watts (Has to be after it has gotten going for the day and is obviously making enough power to stay on) Hold the Left arrow button and push Enter. This should pop up a hidden screen saying In and Out what is the number in the middle of these 2 (Top Middle)? This is the reason for resting at the last switch to Resting. You can even watch it for a bit and see if it changes as it clicks on and off.

I will work on this with boB and we will mock up anything we can comparable to the problem systems and experiment. As I said this just has not seemed to come up other than a few isolated cases and usually it is on arrays that are the same nominal voltage as the battery bank. And this is expected as "Solar" mode is so fast it has a harder time with Arrays that are close to battery voltage and in these cases "Legacy P&O" will be the best choice.

So in closing give me as many details on each problem system as you can (You may already have but I am trying to get tot he airport and then I will look deeper) and we will get our engineers thinking.

Ryan

[JerryB]

Many thanx to Ryan and Damani for the quick response. Here are some specifics:

The controller was bought in January of this year; I don't know the S/N off hand, but I'll look this morning and report back. I *think* the firmware date is sept of 2011. The observations I have made were via the MN local application (great ap BTW), and like Damani, I spent a lot of time monitoring it while I was driving the boat and at the dock. Also like Damani, I used the "dynamic" mode which seemed to be better at times. The PV string voltage is 90 and the battery is 12, so nowhere near equal. I also set the "force sweep" parameter to one minute which tends to limit the time it stays in the weird space, but does not seem to prevent it. The controller displays the "partial shaded" icon when it gets in the weird space if that's important. Some other details: the PV array is about 2100 watts (STC), but they are mounted horizontally (it's a boat...) so full output is rare/unlikely. Perhaps the software thinks it is shaded since the wizard asked for details on the string configuration. With full sun, the controller can easily max out at 95 amps and does so for hours (WITH and only with external cooling BTW; another issue). Let me know if you need anything. If you want gory technical details, just ask since I am an electrical  engineer and worked in power systems for Intel.... Again many thanx.

Jerry

[dapdan]

Jerry,

If you go into the local application and check tab config and then select bottom tab classic you will see all the details of the classic including serial number and the firmware revision.

1/2,

My two classic (I have sold one and need to replace it with a lite when they are available...in fact I a looking at get 2 or 3 of them once the price is right...I digress).

Classic serial # 818
Firmware: classic 910
network 783


Classic serial # 899
Firmware: classic 807
network 783

For both classic I have never altered the sweep times. As for the set up I charge a nominal 24V bank and I use the 200w evergreen low voltage panels which give me a string Vmp of 108V. All arrays face the oreintation no shading facing south.

Cheers...
Damani

[JerryB]

Damani,

I just went to the boat and looked for the S/N using the MNGP and couldn't find it right away. I didn't have my laptop, so the local ap was not available; I'll do what you suggest when I get the chance. The firmware dates were june of 2011 for both the classic and the MNGP. I understand you're in the carribean...where at, if I might ask? My wife and I were in the Bahamas about 2 months ago.

Jerry

[dapdan]

Jerry,

you may ask indeed. I am in Barbados in the parish of St. Philip.

Cheers...
Damani

[dapdan]

Jerry,

If you press the status button it should take you to a screen where it would show you the firmware on the mngp and the classic. As for the serial number I would look for the sicker on the right handside of the classic it should be there.

Cheers...
Damani