3 hours ago, Deanos said:

then look at a better inverter.

This is not only the best, this is the only option 😄

Yup. will do that... Just not right now. Will have to work as it is for now.

6 hours ago, Deanos said:

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.

Apologies to @Deanos for all the confusing posts - we do tend to dive in deeply, and forget that there are also "normal" people on the Forum...

You do have a challenge finding the Goldilocks system that is "just right" for your unique situation:

• You already have a 24V PWM type inverter, and that does not work well with your modern high-power solar panels

• Upgrading to a modern hybrid-type inverter than would work well with your solar panels will require a 48-52V lithium battery (very expensive...) AND perhaps two more solar panels of the same type, and facing the same direction - you have confirmed that this is not a viable option

• Adding another battery or two would work if you are prepared to charge them from the grid, especially in winter, but this will be rather expensive

• Buying a simple generator to charge your existing batteries would also work, but would again be costly. I had such a system with my old 24V 2.2kW original inverter that I ran for nearly 10 years without solar panels, and that worked perfectly for me. My inverter was powered from a normal mains plug socket, and whenever I wanted to charge the batteries (I still had a bank of 12V lead-acid batteries) I would just plug a lead into the generator, and plug the inverter into the other end, and everything worked fine.

Can I just bug you with one more question/suggestion: Looking at the two photos that you uploaded, there appear to be sufficient space for one solar panel in landscape orientation across the center section of your house above where your two panels are currently mounted. Judging by the size of the panels in the photo, you should easily be able to mount two panels either side of the center ridge. If this would be possible you would be able to upgrade to a 3kW, or even 5kW inverter with 4 solar panels if you buy just two additional units of what you currently have. This will be more costly than the additional battery, or the generator options, but will save you money in the long run by putting your study completely "off grid", and even supplementing the rest of your house - think about it...

On 2026/06/29 at 4:57 PM, 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.

From the screenshots and what the others have said, your biggest immediate win is probably setting 29 (Low DC Cut-off Voltage). Long-press Enter on the inverter, scroll to 29 and drop it to 21V or 20V (the lithium batteries can handle it). Right now it looks like it’s cutting out way too early (around 24V+), which is wasting a big chunk of your usable battery capacity.

1 hour ago, Dafne1Schippers said:

From the screenshots and what the others have said, your biggest immediate win is probably setting 29 (Low DC Cut-off Voltage). Long-press Enter on the inverter, scroll to 29 and drop it to 21V or 20V (the lithium batteries can handle it). Right now it looks like it’s cutting out way too early (around 24V+), which is wasting a big chunk of your usable battery capacity.

Thank you, yes, even 22V as I see it roughly gives about 4-5 hours per volt drop with our current load which is around 16 - 20 hours from full battery, so dropping it another 2 volts would be awesome!

I have changed the one setting to run 24/7 from the grid and only use solar first to charge!
This way I should still save electricity, especially after an outage!

To now have to go spend 10's of thousands again is just not happening.

Thanks again for the advice, I'll have a go at pushing the various buttons and see what happens. 🙏🙏

7 hours ago, HennieL said:

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

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...

3 minutes ago, Deanos said:

Thank you, yes, even 22V as I see it roughly gives about 4-5 hours per volt drop with our current load which is around 16 - 20 hours from full battery, so dropping it another 2 volts would be awesome!

I have changed the one setting to run 24/7 from the grid and only use solar first to charge!
This way I should still save electricity, especially after an outage!

To now have to go spend 10's of thousands again is just not happening.

Thanks again for the advice, I'll have a go at pushing the various buttons and see what happens. 🙏🙏

7 hours ago, Dafne1Schippers said:

From the screenshots and what the others have said, your biggest immediate win is probably setting 29 (Low DC Cut-off Voltage). Long-press Enter on the inverter, scroll to 29 and drop it to 21V or 20V (the lithium batteries can handle it). Right now it looks like it’s cutting out way too early (around 24V+), which is wasting a big chunk of your usable battery capacity.

On this point we seem to be on the same page. The only problem I see after I suggested the same is that by lowering the cut off from 24V to a low 20V does not provide the same power as it is in the area of the SOC falling off the cliff.

So far a varied view on possible solutions.

Adding more panels which might not be possible but @HennieL suggested a +1 going landscape above or/and below the current panels. If there is anywhere on the roof that one can fit more panels of say 167cmx90cm or smaller I will outline my suggestion.

Some other suggestions like a genny (costly and noisy) or more batteries while the current PV is already lowish to fully charge is costly.

May be space for a 167x90cm panel on another portion of the roof = R1300 for 330W (Vmp=36V) providing 1.6kWh/day average per year in full sun for Gauteng. Experienced installer to connect this panel to a MPPT controller that cost R900 for a smart Victron 75V/15A. This controller charges the battery directly. This controller has got a lithium profile. Thus the yield for loads and charging is greatly improved from the current system.

This controller can actually even control charging on a 585W panel but will only allow about 420W charging directly to the battery. Very low loss compared to the current PWM.

Yes the OP was advised correctly that panels in series where even I panel in the shade has a major affect on the whole series string.

While typing this I guess even using 2 of the above controllers at R1800 fed from each of the current panels via the MPPT tech might improve charging. This is not qualified advice without having access to the data of the current system. Charging can then be 29V x 2 x 15A. The Victron 75/15 is by far the mostly used controller for lower voltage PV systems in the 12/24Vrange.

@Deanos

Edited 6 hours ago6 hr by Scorp007