MNWBJR feedback

[dgd]

Aw dgd, where would you be without a little excitement once in a while

on my sun lounger in a quiescent state of inebriation satisfied in the knowledge there is order in the universe, God is in heaven and my MN stuff makes  abundant electric power and hot water. 

[zoneblue]

What and never get the hydraulic crimpers out ever again? Youd miss the sweet jingle of lugs, you know you would.

[cybermaus]

So after a few days running with cloudy days battery/SOC% slowly dropped.

2 evenings ago, it finally reached 50% and switched to shore power. Overnight it dropped another 2%, but that is possible as I do still have about 1 amp usage even when the inverter is not active. Also, my Mastervolt manager was a little more pessimistic as it was at 43% in stead of 48%, but I may need to check all the Mastervolts' settings.

---

So far so good. But now the problem: Yesterday was a very sunny day. And yet, it barely charged. 10Amp peak, about 5% SOC back. A day like yesterday, even when winter with low sun, should have been able to put 20% (subjective estimate) back into the bank with 10 Amp average.(equally subjective estimate)

I noticed some people reporting some stuff in the beta thread, there is even already several newer builds. But I do not fully grasp all the items reported or the fixes applied.

So my question: is there already knowledge about something in the latest production release that could cause bad performance? Should I try some of the beta code?

Also I saw that even the 'production release' had a new build number, without there actually being any addition to the 'whats changed' description. Makes me a little extra unsure, updates without descriptions? Was the previous production release 1759 a dud?

PS; Today is another lousy winter-day, so today is not a good day to test or measure individual cables and PV's anyway.

[zoneblue]

Also, my Mastervolt manager was a little more pessimistic as it was at 43% in stead of 48%, but I may need to check all the Mastervolts' settings.

Firstly SOC *is* rocket science. Both Ah devices are dealing with a fickle chemistry, make a broad range of assumptions and use 'good enough' algorithims. Never rely completely on any SOC product. Always keep an eye on rest battery voltage, and get to know its nuances. That and charge state, absorb duration etc are the real acid test of whats happening.

Yesterday was a very sunny day. And yet, it barely charged. 10Amp peak, about 5% SOC back. A day like yesterday, even when winter with low sun, should have been able to put 20% (subjective estimate) back into the bank with 10 Amp average.(equally subjective estimate)

As a rule of thumb, if you cant fully charge your bank on a single sunny day the battey to panel ratio is out of whack. Is that usual or you are saying your system doesnt seem to be charging right? Which controller are you using, and whats the rest of your gear? Sig needed.

I noticed some people reporting some stuff in the beta thread, there is even already several newer builds. But I do not fully grasp all the items reported or the fixes applied.
So my question: is there already knowledge about something in the latest production release that could cause bad performance? Should I try some of the beta code?

Dont worry about firmware at this point, nothing in recent times (or ever, in the case fo the classic)  affects basic charging functionality.  Time to do some testing and diagnostics.

[cybermaus]

Oh yeah, PV to battery ratio is probably not ideal when seen from Solar point of view.

Historic reasons. Its a 100 year old river barge converted into a houseboat, still sailing but lived on permanently (by my sister and her partner)
Battery bank is sized for living off at least 48 hours (with reasonable comfort) without going lower then 30%, and charged by either the main engine (a WWII slow running Lister) or shore power (when available). This was all setup some 25 years ago though the bank is renewed every 8 years or so..

Solar was added only last year, and the amount of panels is limited to what was possible to place on the decks without harming the classic look and feel of the barge. There are rules to what you can do and still be designated 'original' by the various relevant organisations and (even more important) peers. I was arguing to fit 8 panels, but that was rejected on aesthetic grounds. And well, its not my boat.

Not only that, but the panels are angled wrong (13 degrees, should be 30) and there are always sailing boots passing (shadows from masts, its amazing what even a narrow mast shadow can do to a panels efficacy). And when sailing, who knows where South is going to be, though during winter they are on a fixed place.

In specifics:

Six 250W panels making 1500W in total on 24V-480Ah. So no, one sunny day will not fill them up. It will take two days in summer.
And the sun is still low, it is still winter, but I thought the 5% SOC gain really too low. I had expected 20%



Anyway, if this is not likely caused due to the firmware change, I then I will not start doing unneeded updates.  Maybe there was more shadow then I had thought. I best keep an eye on the matter though, and start checking the panels and wiring the next sunny day.

Thanks

[cybermaus]

PS:

... are the real acid test of whats happening.

Was that pun/reference accidental or intended.

[Halfcrazy]

Oh yeah, PV to battery ratio is probably not ideal when seen from Solar point of view.

Historic reasons. Its a 100 year old river barge converted into a houseboat, still sailing but lived on permanently (by my sister and her partner)
Battery bank is sized for living off at least 48 hours (with reasonable comfort) without going lower then 30%, and charged by either the main engine (a WWII slow running Lister) or shore power (when available). This was all setup some 25 years ago though the bank is renewed every 8 years or so..

Solar was added only last year, and the amount of panels is limited to what was possible to place on the decks without harming the classic look and feel of the barge. There are rules to what you can do and still be designated 'original' by the various relevant organisations and (even more important) peers. I was arguing to fit 8 panels, but that was rejected on aesthetic grounds. And well, its not my boat.

Not only that, but the panels are angled wrong (13 degrees, should be 30) and there are always sailing boots passing (shadows from masts, its amazing what even a narrow mast shadow can do to a panels efficacy). And when sailing, who knows where South is going to be, though during winter they are on a fixed place.

In specifics:

Six 250W panels making 1500W in total on 24V-480Ah. So no, one sunny day will not fill them up. It will take two days in summer.
And the sun is still low, it is still winter, but I thought the 5% SOC gain really too low. I had expected 20%



Anyway, if this is not likely caused due to the firmware change, I then I will not start doing unneeded updates.  Maybe there was more shadow then I had thought. I best keep an eye on the matter though, and start checking the panels and wiring the next sunny day.

Thanks

Not likely a firmware issue. My money is on shading. Try this. Go into the Mode and switch it to Legacy P&O it will deal with shading much better than solar mode.

Ryan

[Halfcrazy]

Did you update this Classic previously?
I would check the Input and output current limits in the Limit menu. In should be 99 and Out should be the Max.

Also whats the VOC of the array?

[cybermaus]

The array is in 6 strings of single panels. Though I can relatively easily switch them in 2 threads of 3 configuration, Wiring is in place for both.

I have specifically configured them in 6 parallel panels to reduce shadow impact. Each string is terminated with a diode. If one panel shades, it does not pull the entire string low (or at least, the entire string is just the one panel). There is a bit of extra diode and cable loss of course, but it seems to work well. Or at least, worked well last year.

I specifically got panels of VOC of 42 Volt and MPP of 36 Volt for this reason, so even a single panel is still some distance above the 28.8 volt battery bank.

I did try last year with both the 2x3 and 6x1 config, and the 6x1 seemed to work best.

---

Yes, I did update last week, for the SOC%/WBJr. I did do a factory reset, as advised. I can check those settings next week, I am out of the country at this moment.

[Halfcrazy]

I agree the 1 panel per series makes the most sense. Like I say try Legacy P&O mode instead of solar I bet you see a big improvement

Ryan

[cybermaus]

Well, as stated I am out of the country, so did not do anything yet. But I did read the relevant manual section. And if you have some time, I would not mind some further confirmations/explanations.

Also you may want to review the manual, there is some duplicate/difference between pages 34 and 62

Solar
This is the default mode for PV systems and has a very fast sweep (typically1/2 second or less) that will
re-sweep at user adjustable sweep intervals, unless the Classic finds that it needs to do a sweep on its own
because of changing conditions. The timed sweep interval is user adjustable and is in units of
minutes. SOLAR mode is typically best for PV systems, especially if there is partial shading at times
during the day. The Classic will show a message of "PV SHADE" if it thinks the PV array is partially
shaded (if this feature is enabled).
SOLAR mode is best suited for shaded or un-shaded PV arrays that are at least one nominal voltage above
the battery voltage. For severe partial shading or PV arrays with nominal voltage equal to battery voltage,
you may also want to try Legacy P&O (Perturb and Observe) MPPT mode. 

Legacy P&O (Perturb and Observe) mode is a slow tracking mode similar to the Micro Hydro mode but
with the difference that it is slightly faster and will shut off if the power source goes off.
It has 2 settings that are user adjustable. Sweep Interval is the time between mini-sweeps, in minutes, and
sweeps around the present (i.e. the last found), MPP Voltage. The range of this sweep is determined by
the Sweep Depth user adjustment and is expressed as a percentage of Watts that the sweep started
from. For example, if in Legacy P&O mode, the Classic was outputting 500 Watts and the Sweep Depth
percentage was set for 10%, (50 Watts), the sweep will bring the input voltage DOWN until the output
power drops down to 450 Watts, then will sweep UP in voltage until the power drops again down to 450
Watts and then go back to the newly found MPP Voltage, waiting for the next sweep.

Solar
[word for word the same]

Legacy P&O
Legacy P&O (Perturb and Observe) mode is a slow tracking mode similar to the Micro Hydro mode but
with the difference that it is slightly faster and optimized for Solar. Legacy mode can be very usefull for
arrays that experience heavy shading issues as well as PV arrays that have a low voltage. If the array has a
VOC (Open Circuit Voltage) of less than 125% of the battery voltage Solar mode will not work as well so
Legacy will be a better choice.

I am interpreting "one nominal voltage above the battery voltage" as "just over twice the nominal battery voltage" ? So I guess between 200% and 125% of battery voltage is a gray area, but below 125% definitely go legacy. And with all the shading and just over 125% that I have, also go legacy. Still, solar mode seemed to work well last year.

The manuals descriptions seems to make sense. Actually, one of the reasons I was pushing for 8 panels is so I could organize them as 4x2 and have a 72Vmp, with 4 strings / 'shading blocks'. It's also why I selected the 200 model, so I could potentially also try 2x4 in that case. But as stated, we have 6 panels, and unless I have a really good reason to get 2 more, aesthetics means it will stay at 6 panels.

I do want to remark that though random shading is an issue, because of the diode wiring, the array does not actually reacts in a typically shaded manner. If one panel gets some shade, it drops voltage, but due to the diodes, the overall array voltage stays pretty high. The shaded panel of course also tries to match that, so it completely falls of at the steep end of the curve and drops current. It may be better if the Vmp would be slightly lowered, so all panels keep up current at a slightly lower Vmp

Is that what the P&O would achieve better? Text seems to indicate the Solar MPPT is more aggressive, maybe too aggressive, and the P&O less aggressive in how far it sweeps the Vmp. I will follow advise and try the P&O, I am just fishing for a better understanding of what it is I will be trying.

---

I found another document with "Watt-Voltage table"
In it there is not even a discussion of any Vmp below 70V and even 70Vmp is na for the 150 model. What is up with that, is the Classic really not ideal for single panels, and am I pushing the (low end of) the envelope?

---

PS : not critical, but I do have a self made shunt installed pre-diode with each of the 6 panels, so I can see per-panel potential and current.

[vtmaps]

I am interpreting "one nominal voltage above the battery voltage" as "just over twice the nominal battery voltage" ?

I have also wondered about this. 
Check out Midnite's string calculator.  I set up a 1 panel array on a 12 volt system, and then reduced the Vmp until the calculator alerted me that the Vmp was too low.  IIRC, I got down to 14 volts.

--vtMaps

[boB]

I am interpreting "one nominal voltage above the battery voltage" as "just over twice the nominal battery voltage" ?

I have also wondered about this. 
Check out Midnite's string calculator.  I set up a 1 panel array on a 12 volt system, and then reduced the Vmp until the calculator alerted me that the Vmp was too low.  IIRC, I got down to 14 volts.

--vtMaps

Yes, you basically have the right idea on 2wice the nominal voltage of the battery but PV modules used to be rated
with battery voltage numbers before all this grid tie terminology took over.   There was a 24V PV module or a 48V or
12V module designation.  That is kind of what I meant.   So for a 48V battery system, you would choose a 60V PV array.

Now it's a bit different.  Number of cells instead of battery voltage pretty much is what I have been seeing.

boB