Well I just did it manually myself with my calculations in this post above: What conditions make it ok to have uneven strings of paralleled panels? - #7 by letslearntogether
Do you see any problems with the above proposal? I don’t know what the climate skeptic who replied above is referring to about the fuse problems really if you have any idea if that is a genuine concern?
Hey guys the setup had been running great since the time I have set it up a few months ago though recently I noticed something strange. Suddenly the MPPT has decided to drop to NO output and the MT-50 status will be showing it is still night time at 0/1V!!! I thought this was just due to clouds or being too early but today it went all the way to 2pm and still showing night time so I thought something is up here.
I then checked with the multimeter on the solar wires and there was current running between the two strings (I was told by someone this is because of the voltage differential between the two strings and just a harmless effect of that) but then nothing after the Y connector junction so the MPPT was deciding to keep them off. It is not because the battery is full as it was about 70% at a guess. Also what I then tried was to disconnect one string and try again and lo and behold the MPPT works and gives current again. Try the other string, and same again. So they both work but decided to not play nice for some reason.
I am wondering, could it be that one or more of the panels on the 300W string has died and so the overall voltage on that one is causing the whole combination to be so low to shut down the MPPT?
After my above tests they both started working again when I connected them together and tried again. Don’t know if it was just fluke. It does still work every day at some point that I know of but it seems that it is shutting down for hours sometimes. Maybe it has always done this and I wasn’t paying attention before. I think on sunny/fairly good weather days it doesn’t do this, at least not for any long period of time. I seem to recall that the couple of times it has happened, that I noticed, has been early in the morning before the panels get direct sun, or when it is cloudy.
Any ideas what might be happening? I had noticed it happened the other day too and just thought it was because it was too early and then when the sun hit they worked but from today, seeing that it took until 2pm to suddenly get output, maybe only after my fiddling with it, not sure, it seems there is more to it.
Is it just that sometimes the MPPT might be confused and not find an output that can make them both work and so shuts down until it does? I thought from earlier advise that in these cases it would just choose the higher panel’s voltage which just cause the smaller array to shutdown, not both. Or is that not necessarily the case?
Check with a thermal camera.
I would be keen to see your panel output figures compared to your installed and where the vmp and current has been tracking compared to the panel specs etc.
With mismatch one lot will produce the other not so much sometimes not at all. Depends on if the mppt wants to try use the higher vmp or the lower.
Or maybe you didn’t note a drop in output because the mppt is over panelled and not likely to be able to spot losees?
Sure, everyone has at least one of those lying around. 
What I see today is that it is ‘awake’ again despite being very overcast and raining now. So I am not sure what is triggering it to happen in the other cases where it switches off. I am not getting any significant output but the pv light is on and showing voltage on the panels, albeit only about 14v and no energy to speak of (below 0.6A) but in the cases where they are not working the PV light will be switched off and the reader will show near 0V and nighttime status.
I have not found rhyme or reason for this happening. I didn’t notice it for several days and cropped up again today. I was not able to get them to both work again this time so I just disconnected the smaller array to leave the main array running. Reconnected now, just at sunset and they both work again, although the solar is finished for the day, they show voltage again with both connected rather than showing nighttime 0V. 
Hmm I just noticed some weird behaviour which could be related to the issue…
I went to go turn off the electrics and back on again using the main battery isolator switch and … the power did not shut off. The mppt reader stayed powered. I then switched the PV disconnect to off and that did switch things off - so it seems the pv power is still sending power to circuits in some measure independent of the battery.
Is this normal or abnormal?
Normal.
Victron mppts can power on from pv to wake up or black start batteries and run dc circuits directly. (Depending on load of course surge start ones are not reliable)
Also the reaosn why many people dont notice a blown fuse until their battery is depleted.
Thanks. Lol the victron MPPT feature is what I presumed all MPPTs did, until I found out the hard way it isn’t one time. I was on low battery and thought - no problem I will just let the PV power wake it up if it depletes this evening only to find out this is not a standard thing. I even had a DC charger too but was unaware that also required some form of power from the leisure battery to wake up and charge. I know now this was probably not the case, as there is a setting to force it to send charge even if the leisure battery was too low to be woken up normally, but didn’t at the time.
It was a clear day and the MPPT was not waking up so it was frustrating to see it there and yet not being able to get it into the battery to power the system again, or use the DC charger.
Ended up driving 2 hours back to where I could recharge it from mains.
It was a hard lesson learned. 