HI everyone.

Please bear with me on this, fairly new to the whole solar and backup thing.

I have included images of all the inverter specs, the battery specs and also the WatchPower settings for reference.

Just after lockdown, we purchased this Mecer 3KVa inverter. It has 200AH of back (So they say...) from the 2 included 24V 100AH Lithium batteries.

So due to all the constant outages we have in our area lately, we decided to put up 2 LARGE solar panels. This was done 1st of April this year.

The panels we put in are 2 x TigerNeo 72HL4-BDV 585W solar panels on the roof facing east... It was summer! Yes, I know...

This is all working perfectly, but now a few little issues I have with this whole setup.

Unfortunately, this WatchPower software is all that you can apparently use with this inverter, unless you spend copious amounts on money for that Solar Assistant software. Not happening from my wallet unfortunately...

I have this software installed and running on a little Pi that I had spare here with Windows 10 on so I can remote into it and see what's going on.

I have just taken a screen shot of it which is below and this winter sun is just not the greatest right now.

The settings are the big thing.

Are we just extremely limited to what this inverter can do or how can I set it to keep the batteries as close to full as possible, especially in winter?

Reason is that 90% of the time when the power cuts, it will be late afternoon or at night and the batteries are just never full and then the system cuts off because of that!

It's so annoying and yes, this has been the case for the past 4 outages we had over the past 3 weeks. Then the sun just isn't enough to keep things running the next day and charge the battery...

So (sorry for the long story...) my questions...

1) is there anything I maybe need to tweak in the settings there to get better performance from the batteries?

2) How do I know what voltage the inverter cuts off at and what should it be and how do I set it?

3) Any other free alternatives to this WatchPower software?

Thanks in advance for the help.🙏

Layman's 2c, use at own risk, or get advice. Some points to consider all the same.

You've got an inverter with a 1200W PWM charge controller. In Winter that's just not quite enough to keep the battery charged. On average, touch and go, under the best of conditions in Winter, it's just-just sort of okay, but most of the time not, and if you're intending to run daytime loads from it as well, then you just don't have enough power generation capability. On top of that your setup is likely not optimal to begin with.

I'm assuming that your 2 x panels are connected in parallel, or it would have exceeded the inverter's max VOC and caused a failure. If this is not already in parallel, you really should change it over to parallel. But your panel's Vmp isn't ideally matched to the inverter. Better would have been to use a panel like the Canadian Solar HiKU6 CS6W405MS panel (x3), because the Vmp spec is better aligned with the battery charging Voltage. Unfortunately you've got a 25% loss of efficiency with the current panel right out the gate.

You could lower the discharge cut-off Voltage to 20V (spec as per the battery), ie. discharge it deeper than the inverter is doing now. And then I think you should change from SBU mode to utility mode, ie. just keep the battery and panels on-hand as a loadshedding solution, without trying to power the whole house from it permanently.

You'd have to do a more drastic upgrade, like changing to a 24V MPPT-controlled inverter, and adding maybe another two panels, before you can start thinking of running daytime base load and then still charging the battery by day for draining at night.

Thanks for this. Yes, panels were all installed to spec by the solar specialists. They also recommended we go with those 2 panels due to the space on the roof. Limited there unfortunately.

But I see the battery spec or sticker says it can go down to cut-off at 20V, but how do I know if the inverter is cutting of at 21 or 22V?
I have a feeling the inverter is shutting off around 24V.
Maybe a safety net or something that the GeeWiz guys reconfigure in the inverter?

Can this be checked and changed somehow?

43 minutes ago, GreenFields said:

Layman's 2c, use at own risk, or get advice. Some points to consider all the same.

You've got an inverter with a 1200W PWM charge controller. In Winter that's just not quite enough to keep the battery charged. On average, touch and go, under the best of conditions in Winter, it's just-just sort of okay, but most of the time not, and if you're intending to run daytime loads from it as well, then you just don't have enough power generation capability. On top of that your setup is likely not optimal to begin with.

I'm assuming that your 2 x panels are connected in parallel, or it would have exceeded the inverter's max VOC and caused a failure. If this is not already in parallel, you really should change it over to parallel. But your panel's Vmp isn't ideally matched to the inverter. Better would have been to use a panel like the Canadian Solar HiKU6 CS6W405MS panel (x3), because the Vmp spec is better aligned with the battery charging Voltage. Unfortunately you've got a 25% loss of efficiency with the current panel right out the gate.

You could lower the discharge cut-off Voltage to 20V (spec as per the battery), ie. discharge it deeper than the inverter is doing now. And then I think you should change from SBU mode to utility mode, ie. just keep the battery and panels on-hand as a loadshedding solution, without trying to power the whole house from it permanently.

You'd have to do a more drastic upgrade, like changing to a 24V MPPT-controlled inverter, and adding maybe another two panels, before you can start thinking of running daytime base load and then still charging the battery by day for draining at night.

He is limited by space it seems. He could have added a 3rd panel to that inverter but he is now limited by the space.

Sounds like his inverter is set to cut off too low. And he also needs to manage expectations. If running a large TV and a few other things those batteries just wont last at night.

23 minutes ago, Deanos said:

Thanks for this. Yes, panels were all installed to spec by the solar specialists. They also recommended we go with those 2 panels due to the space on the roof. Limited there unfortunately.

But I see the battery spec or sticker says it can go down to cut-off at 20V, but how do I know if the inverter is cutting of at 21 or 22V?
I have a feeling the inverter is shutting off around 24V.
Maybe a safety net or something that the GeeWiz guys reconfigure in the inverter?

Can this be checked and changed somehow?

You can check any setting by a long press of the enter button on the unit. Use the up and down buttons to get to the desired setting. Setting 29 is to get the DC cut out voltage level. Use up and down buttons to change the setting and the enter will save the setting displayed.

@GreenFields the APP settings show 26.6V from panels so luckily the 2 panels are connected in parallel but that makes the system not very efficient as you alerted to.

Edited June 29Jun 29 by Scorp007

1 hour ago, Deanos said:

Thanks for this. Yes, panels were all installed to spec by the solar specialists. They also recommended we go with those 2 panels due to the space on the roof. Limited there unfortunately.

Can you please elaborate on your roof size and layout - it is quite strange to hear of any roof that can only accommodate two solar panels... Don't you also have a roof facing west (or a carport of something facing north...) where you can install another two panels?

Also, you mention that you have two 100Ah lithium batteries installed. Lithium batteries don't like to be drained deeply, and if your system was installed just after covid lockdown then they are already about 6 years old. This would not be a problem if they were only lightly discharged, but if they were regularly discharged deeply then their capacity could already have reduced enough to become troublesome.

Edited Monday at 07:045 days by HennieL
Typo corrected

1 hour ago, Scorp007 said:

the 2 panels are connected in parallel but that makes the system not very efficient as you alerted to.

Thanks for the help. But should the panel be connected a different way to be more efficient then?

17 minutes ago, HennieL said:

Can you please elaborate on your roof size and layout

Sorry, not the best image, but a shot from Google earth.
I circled the 2 panels and North.

Problem is that this section of our roof gets the most sun during the day in summer as the rest of the roof is mostly in shade mornings and afternoon.

I did want to cut down every tree, but the bigger ones are neighbours trees mornings and afternoon, so that wouldn't happen.

We looked at every option, this was the best and most efficient.

3 hours ago, Deanos said:

Sorry, not the best image, but a shot from Google earth.
I circled the 2 panels and North.

Thanks, this helps us to understand your situation.

It's difficult to make out much detail on the photo, but it looks like the panels are on the eastern roof that is actually sloping down to the west, with an east facing roof to the left of the panels... Can you please confirm if this is the case?

Something else to check is the slope of the panels (degrees from vertical) - those panels appear to be quite flat (horisontal), and with the winter sun being much lower in the sky that would explain why your summer yield was OK but the winter yield is much less. Would it be possible to raise the angle of the panels? If you care to tell us where your house is located (town) we can easily calculate the optimum slope for summer, winter, or all-year yield for you.

3 hours ago, Deanos said:

looked at every option

Add two more panels on the eastern side of the smaller roofs, try vertical panels, drill holes in the trees and pour in diesel... Lots of options.

4 hours ago, Deanos said:

Thanks for the help. But should the panel be connected a different way to be more efficient then?

This issue cannot be resolved with a connection or a setting. It is a characteristic of the panel that is not optimal for the inverter's charger type.

Also, considering that the house is already facing around 20 degrees East, those panels are actually facing a bit towards South-East, further reducing the generation capacity. Would there be too many shadows if you fit them to the main roof facing North-East?

Unfortunately you've got a complex situation with possibly no easy solutions.

2 hours ago, GreenFields said:

This issue cannot be resolved with a connection or a setting. It is a characteristic of the panel that is not optimal for the inverter's charger type.

Also, considering that the house is already facing around 20 degrees East, those panels are actually facing a bit towards South-East, further reducing the generation capacity. Would there be too many shadows if you fit them to the main roof facing North-East?

Unfortunately you've got a complex situation with possibly no easy solutions.

It seems like some missed your post indicating a maximum charge of 1200W by the PWM controller.. Even 2 more panels if there was space would not help much.

Current panels already 1170W.

9 hours ago, Scorp007 said:

It seems like some missed your post indicating a maximum charge of 1200W by the PWM controller.. Even 2 more panels if there was space would not help much.

Current panels already 1170W.

My experience with PWM controllers kind of shows otherwise to be honest.

His panels seem to have a Vmp of 42V. The PwM will only make use of 30V from that panel so it really will only pull a maximum of 400W from that panel.

The installer didn’t match the panels to the type of charge controller he has so at best he will get 2/3 from that panel. Had he gotten panels that had a Vmp of around 32/33 then most of that panel would have been used.

So he can comfortably add another 1 or 2 panels and then he will start seeing numbers close to that PWM limit. Later on he can change the arrangement of the panels when he switches to MPPT.

I had a PWM once and made the same mistake of buying large panels without matching the voltage to them. I had 4 on mine and did eventually hit the 1600W my controller could do which made things much better for generation. I was still wasting a lot of solar potential as the panels had a Vmp of 42.

PWM isn’t necessary bad, it’s just that installers don’t match the panels to the inverter. I sold my PWM to a friend and specced the panels for it. He gets to about 90% of the panel rating all because the Panels have a Vmp of 32 if I recall. So decently efficient.

8 hours ago, Scorp007 said:

It seems like some missed your post indicating a maximum charge of 1200W by the PWM controller.. Even 2 more panels if there was space would not help much.

Current panels already 1170W.

I respectfully disagree. Inverters can accommodate some over-supply, as they just limit the input. Even if this inverter cannot do so, the maximum output power of the panels is at standard testing conditions, which might be achieved in some places in South Africa at the peak summer time between 12:00 and 13:00. It is highly unlikely that the panels would produce this power at the rather flat slope (vertical angle) that they are installed at - and the azimuth angle is also working against this. I would be very surprised if the panels can even reach 50% of this rated power...

What I do note when comparing the specifications and output information provided by @Deanos in the first post is the following:

• Solar charge module rated current = 50A @ 24V

• Charge module VOC = 80V

• Solar charge module operating voltage range = 30V - 32V

• PV input voltage (measured) = 26.6V

• PV input current = 11.0A

It is clear that the PV input voltage is below the PWM operating window. At the time the measurements were taken, the batteries were being charged at approximately 26.6 V × 10 A = 266 W (about 0.05C for a 200 Ah battery bank). A 24 V, 200 Ah battery bank stores approximately 4.8 kWh of energy, and charging from 50% to 100% SOC would require about 2.4 kWh of power. At a constant charging power of 266 W, this would theoretically take about 2400 Wh ÷ 266 W ≈ 9 hours. In practice, however, charging will take even longer because the charging current tapers during the absorption stage, and the available solar power varies throughout the day.

@Deanos can you please confirm if the PV input voltage reported by the inverter is the true input voltage (as stated in the last screenshot of your first post), or is this the voltage of the batteries being charged? According to that last image, the battery voltage is reported as being 27.03V, and if that is the case then the batteries were not being charged at all at the time of measurement...

From all the above, it would appear that your system would have worked better with older solar panels that have lower VOC ratings, where you could connect two panels in series, and not in parallel (you cannot do that with these panels as this will exceed the critical VOC limit), and with perhaps a second "string" of 2 series connected panels then paralleled with the first "string". If you cannot do this, then the only option left would be to face the panels correctly (facing close to north, and at the correct slope (between ~30 and ~40 degrees from horisontal, depending on where you live)).

PS. This is assuming that the panels are in fact connected in parallel - if connected in series the I agree with what @Denns said above (I was busy typing when he posted...) BUT then there is a real risk of exceeding the VOC limit in winter...

Edited Tuesday at 06:565 days by HennieL
Added a PS

OK WOW. Thanks for all the comments and to be brutally honest, I have ZERO clue of what you are all on about. 🤣🤣🤣🤣

Let me try explain the whole idea behind this setup.
We started off with the little 3KVa Mecer invert. This works like a bomb and keeps things going on it's own for at least a day and bit from full battery.
At the most, we pull maybe 300W to 400W from it.
It is NOT wired to the mains because I didn't want to worry about COC and the whole Eskom saga and also would like to be able to take it with me when I move one day!
So I have my entire study running off it, an extension through to the lounge so the wife can still watch TV, and a 2nd extension to our bedroom upstairs so we can at least have power there if it's off.
And before you all go off about the cables, they are all proper 7mm or 8mm power cable. Not a Temu extension... 🤣🤣🤣

Anyways. The power cuts here in Weltevreden Park are now becoming a weekly thing as the whole infrastructure here is collapsing. Much like the rest of the country...

I knew the inverter would take a max input of 1200W from the solar, so I then explained to the installer that I wanted 2 of the biggest wattage panels they have so I can get as close to the limit as possible. Hence the 2 x 585W panels... 1170W total. Yes, I know about total efficiency and all that so was hoping to at least be able to pull 900 - 1000W from them.
Install was done, everything plugged in and working on 2nd April and back then with the summer sun, I was hitting just on 750W max on a good day so I was almost happy.

So yes, I have attached 2 picture below to give a better idea of were the panels are and why I can only get 2 on there.
It's a stupid roof and I wanted to put 2 more panel;s on the other side of the roof facing west (Camera is currently facing to the west and panels facing to NE), but I was told that you can't slip panels because if 2 are in the shade, the others stop working also?!?!?!
It was a bit of a debate whether we wanted to get the early morning / midday sun or midday / late afternoon sun. We chose the early morning rather... Rain usually happens afternoons here.

I have ZERO clue how solar works, how the Watt and VAC and VOC and what what means, so like any normal pleb, I have full trust and faith in that when installer tells me.

So yes, unfortunately this is now all installed and done and was a cheap to be done this way also. And unfortunately finances won't let me simple remove and reinstall panels at will.

So was just thinking if there was a setting of sorts on the inverter to allow it to drain or ruin on battery for a little longer than it does now where it cuts off at 24V.

16 minutes ago, Deanos said:

So yes, I have attached 2 picture below to give a better idea of were the panels are and why I can only get 2 on there.
It's a stupid roof and I wanted to put 2 more panel;s on the other side of the roof facing west (Camera is currently facing to the west and panels facing to NE), but I was told that you can't slip panels because if 2 are in the shade, the others stop working also?!?!?!

Thanks @Deanos A picture paints a thousand words...

Your slope angle is not too flat, so that's out of the picture 🙂

It is true that one cannot have one "string" of panels working as expected if there is even just a portion of one panel being shaded, so your installer gave you good advice on that...

He did NOT give you good advice on matching the panels to your inverter. His crucial mistake was not matching the maximum voltage output of your modern, high-power panels (being 52.7V per panel) with the maximum VOC of the PWM of the solar charge module of the inverter (which is 80V). When one exceeds the rated VOC of the inverter module the inverter will become permanently damaged... so, you are limited to only one solar panel in series (one panel feeding through a second panel, the same as (say) two torch batteries feeding one through the second to give the required voltage. One can double the current (Amps) being provided by the solar panels by connecting two or more of them in parallel without increasing the VOC, but panels are more efficient when supplying power at higher voltage. What he did not allow for, was the fact that your panels are not optimally facing the sun (both in terms of slope, and especially in terms of directions relative to the sun's path (called azimuth). Because of this, your two parallel connected panels are not even producing sufficient voltage to reach the ideal "operating zone" of 30V - 32V as stated on the inverter label (your first image posted in the first post). If he had recommended lower rated older technology panels (as @Denns stated he did in his last post above) then ironically you would have been better off, as you could then have connected two panels in series and used most of what they would have produced...

OK, understood, and yes, this was mentioned to maybe have 3 or 4 smaller panels, but when he saw my roof, we then went with the 2 bigger panels.

They are in parallel as mentioned in the earlier messages.

But alas, I guess I am stuck with what I have for now. I am also thinking that maybe a newer more efficient inverter might also be the better option...

46 minutes ago, HennieL said:

Thanks @Deanos A picture paints a thousand words...

Your slope angle is not too flat, so that's out of the picture 🙂

It is true that one cannot have one "string" of panels working as expected if there is even just a portion of one panel being shaded, so your installer gave you good advice on that...

He did NOT give you good advice on matching the panels to your inverter. His crucial mistake was not matching the maximum voltage output of your modern, high-power panels (being 52.7V per panel) with the maximum VOC of the PWM of the solar charge module of the inverter (which is 80V). When one exceeds the rated VOC of the inverter module the inverter will become permanently damaged... so, you are limited to only one solar panel in series (one panel feeding through a second panel, the same as (say) two torch batteries feeding one through the second to give the required voltage. One can double the current (Amps) being provided by the solar panels by connecting two or more of them in parallel without increasing the VOC, but panels are more efficient when supplying power at higher voltage. What he did not allow for, was the fact that your panels are not optimally facing the sun (both in terms of slope, and especially in terms of directions relative to the sun's path (called azimuth). Because of this, your two parallel connected panels are not even producing sufficient voltage to reach the ideal "operating zone" of 30V - 32V as stated on the inverter label (your first image posted in the first post). If he had recommended lower rated older technology panels (as @Denns stated he did in his last post above) then ironically you would have been better off, as you could then have connected two panels in series and used most of what they would have produced...

Sorry I think you misunderstood me. PWM likes current vs an MPPT that likes Voltage. So for PWM, Parallel panels are best actually, not series. He actually has "too much" voltage from those panels even though he is in parallel. The best configuration for him would be panels with a voltage no more than 32V or so but a lot of current. So perfect scenario for him assuming such panels existed would be 2x800W panels, each with a Vmp of 32V and Imp of 25A each. Both in parallel to keep the voltage at 32 and the current would be 50A.

But alas such panels dont exist. So the next best thing would be to get 400/450W panels with the Vp of 32V and current of about 13 to 15A. Wire all 3 in parallel. 2 400W panels with such specs would get you the same results as 2x585W panels like he has.

In his case though small or big panels would make no difference as he can only do 2 panels unfortunately.

PWM brings the panel voltage down to the battery voltage.Whatever excess voltage it sees from the panels goes to waste basically.

Thanks again.

Now assuming "he" even understands what you are talking about here, does that mean the he, or I, must now go and buy other panels in order to let my batteries drain a little bit more (as per my original questions!) or what is it that you are actually on about?

We, he, me, us, I just don't understand where this is all going.

Do I now chuck out these 2 big panels and buy a different panel which you now say doesn't exist, or would it be more efficient to just get a newer inverter of sorts that will work with my 2 panels?

2 minutes ago, Deanos said:

Thanks again.

Now assuming "he" even understands what you are talking about here, does that mean the he, or I, must now go and buy other panels in order to let my batteries drain a little bit more (as per my original questions!) or what is it that you are actually on about?

We, he, me, us, I just don't understand where this is all going.

Do I now chuck out these 2 big panels and buy a different panel which you now say doesn't exist, or would it be more efficient to just get a newer inverter of sorts that will work with my 2 panels?

No, you dont have to do anything on the panels side. You said you cant put panels anywhere else so you are limited there.

24V is already low enough by the way. You wont get anymore out of the batteries so leave it there please. It will just damage them running them further down to 20V.

You basically have 2 choices, limit usage when power cuts occur to make the batteries last longer. Or buy another 1 or 2 batteries which becomes expensive.

Personally, I would just buy a generator. The cheapest 4 stroke you can buy. Run it for 2/3 hours to charge up the batteries to full. You can do that around 3pm to top up the batteries with whatever the solar couldnt finish charging up.

No noise at night. And because you have solar, the generator just acts as a top up and not the sole source of charging. You can get a cheap 4 stroke for about 4k. Try and get at least a 2.5kVA and only run it around 60% of its load.

You would need to set the input of the inverter to APL to accept the generator also. They can be a bit finicky with Generator sources but can be made to work. Also connect a load to the generator before connecting to the inverter. Thats another trick to get it the inverter to accept the charge.

Edited Tuesday at 09:315 days by Denns

8 minutes ago, Denns said:

No, you dont have to do anything on the panels side. You said you cant put panels anywhere else so you are limited there.

24V is already low enough by the way. You wont get anymore out of the batteries so leave it there please. It will just damage them running them further down to 20V.

You basically have 2 choices, limit usage when power cuts occur to make the batteries last longer. Or buy another 1 or 2 batteries which becomes expensive.

Personally, I would just buy a generator. The cheapest 4 stroke you can buy. Run it for 2/3 hours to charge up the batteries to full. You can do that around 3pm to top up the batteries with whatever the solar couldnt finish charging up.

No noise at night. And because you have solar, the generator just acts as a top up and not the sole source of charging. You can get a cheap 4 stroke for about 4k. Try and get at least a 2.5kVA and only run it around 60% of its load.

You would need to set the input of the inverter to APL to accept the generator also. They can be a bit finicky with Generator sources but can be made to work. Also connect a load to the generator before connecting to the inverter. Thats another trick to get it the inverter to accept the charge.

Best value for money generator which wont give issues with the inverter accepting the charge is this one below. Thats what I could find.

22 minutes ago, Denns said:

You would need to set the input of the inverter to APL to accept the generator also. They can be a bit finicky with Generator sources but can be made to work. Also connect a load to the generator before connecting to the inverter. Thats another trick to get it the inverter to accept the charge.

OK, this just sounds extremely confusing. 🤣🤣🤣 I don't have the expertise or money right now to firstly get a genny, and then also have to mess around with the inverter settings. This is basically an explosion in my house waiting to happen if I do that!

Looking around at other inverters, they are much the same pricing as a smaller genny and don't use as much petrol either! 🤣

So i think the best answer right now is to just leave the system as it is, maybe get another 2 x 100AH batteries and hook them up so we then have a 400Ah capacity. then look at a better inverter.

7 minutes ago, Deanos said:

OK, this just sounds extremely confusing. 🤣🤣🤣 I don't have the expertise or money right now to firstly get a genny, and then also have to mess around with the inverter settings. This is basically an explosion in my house waiting to happen if I do that!

Looking around at other inverters, they are much the same pricing as a smaller genny and don't use as much petrol either! 🤣

So i think the best answer right now is to just leave the system as it is, maybe get another 2 x 100AH batteries and hook them up so we then have a 400Ah capacity. then look at a better inverter.

Lol, sorry about that🤣.

The problem with adding more batteries is that you are using more than the panels can provide. So you will still just drain them if the powercuts are a bit longer. 300/400W from your bank means about 10 hours of run time. Your solar you said peaks at 700W on a good day. That doesnt leave much for the batteries. Thats why i recommended a generator.

An MPPT inverter would be better. And you may get closer to 1000W but you still need to keep an eye on your loads.

They still charge from utility, not 100% from solar when the power is on, so should be all good.

It's a matter of it all just hanging in there when the power is off.

This is current usage as of right now:

Edited Tuesday at 10:135 days by Deanos

Thanks to @Denns and @HennieL that explained why @GreenFields and myself mentioned the combination of the PWM controller and high voltage panels make for a very inefficient charge system.

I merely meant the panels are 1170W but due to the controller it will use only about 400W for charging.

As per specs for the controller is given as 50A at up to say 24V is where we find the maximum that the controller can charge.

This is how I see it and always open for inputs. @Denns explained very well how the PWM controller would pull the panels down to about 29V for charging the battery. The excess volts is thus lost while a MPPT would use the full volts.