Hello everyone!

I live in a region where it is very hot in summer, and the infrastructure still leaves much to be desired. To solve the problems with the lack of electricity, I installed a solar power station. But I assembled it with a reserve (about 3 times more than my needs) for cloudy or short winter days. I also planned to export the surplus to the grid.

For about a month now I have been struggling with:

1. too hot air around the inverters (the outside air temperature is over 40'C)

Because of this, both inverters overheat (the temperature of its sensors reaches 70-75'C) and, as expected, begin to throttle. One inverter produces approximately 80% compared to the time when the air temperature was below 30'C. And the second, on average, produces only 50% of what the first inverter produces at the same time. And this behavior was from the factory / the moment the inverters were installed.

2. Another problem is that the voltage in the power grid is very low (about 180V with a standard of 220V)

Three phases come to my house, and such low voltage during the day on all three phases (not evenly, but with an imbalance between the phases 180V - 190V - 160V).

When the voltage drops to about 185V, other inverters stop exporting. But the mixing of solar energy into the house continues, as expected (this can be seen from the meters before and after the inverters).

At night, the voltage rises to 210V and, as expected, in the morning the inverters cheerfully begin exporting. Until the voltage on the corresponding phase again drops below 185V. And it does not resume until it rises above 200V (i.e. until night).

Problem #1 with incorrect throttling of the second inverter would be something that would be nice to solve, but problem #2 looks even sadder in comparison.

What I have done so far:

• solar panel power: 4 strings of 7 panels with a power of 550 W each (i.e. each string is 3850 W at peak)

• in 2 identical inverters with a power of 11 kW and two MPPT inputs of 5 kW (where each MPPT receives 3.8 kW maximum) clone of Voltronic MAX E 11K

• replaced the power grid cables with more powerful ones and checked them with a thermal imager - the cables do not heat up compared to the surrounding air

• I previously connected a voltage stabilizer before and after inverter, but it ended sadly and I had to repair the inverter (after repairing it works perfectly - throttles 80%)

In other words:

• inverters are loaded only at 77% of their maximum capacity

• they are balanced across solar panels and distributed across different phases of the power grid

• losses between inverters and the power grid are minimized

• the inverters and electricity meters themselves are logged into Home Assistant and are monitored (in parallel with billing of the energy supply organization)

Now the question itself:

I can't tell the inverter to export to the grid, even at low grid voltage (i.e. this behavior does not depend on the "03 AC input voltage range APL\UPS" parameter).

Adding a voltage stabilizer kills the inverter.

I have not seen any firmware for my inverter on the Internet that would fix the described problems.

But, I can open the inverter and "patch" its AC voltage sensors so that it thinks that the mains voltage is still normal - say, so that it sees 180V as 190V.

Does anyone have any thoughts on these unplanned inverter circuit changes? Pros, cons?

Or does anyone have any cheap but smart ideas?

Edited July 5Jul 5 by bobah1248

My thoughts about it is: Get off grid and forget about exporting. Install an extra air conditioner in the inverter room. That would comfort the inverters and potentially extend their life. It would consume part of the produced energy but according to your writing anyhow overflows.

If the inverter disconnects when the grid parameters are out of tolerance, that's surely by design, and probably not a good idea to try to override it. If it still makes financial sense, get more batteries to store power and export at night.

Thanks a lot for the recommendations.

@Beat I asked for cheap solutions 😉, while installing additional air con is not cheap, as well as stop exporting - export gives me an extra 100-150 USD per month (or about 2% of total cost of solar station). It's a pretty good return on investment 😀

@GreenFields Unfortunately, my inverters are not able to export energy from batteries. In addition, this will increase the wear of the batteries, which will not be covered by the cost of grid electricity in any way.

I have plans to install water liqiud cooling for inverters - this should not only be cheaper during modernization, but will also allow me to save on hot water for household needs. Yes, in my area there is no centralized supply of hot water, so heating water and accumulating it could make sense.

And this is one of the reasons why throttling worries me less than export stability.

Edited July 5Jul 5 by bobah1248

I think your main problem is that clone inverters?

@Demo I'm not sure that the problem is that the inverter is a clone.

I'm 99% sure that the main firmware is not the same as the original. And I'm interested in whether there is a problem with export in other inverters (including original ones).

The answer to this question could rather be given by someone who is familiar with the firmware from the inside, like @Coulomb

Question: do the inverters have anything to do with the grid when voltage is low?

My inverter is set for the South African grid code. In terms of voltage this is is nominally 230 with 10% allowed either side. So 253 to 207. My inverter does not stick to precisely that, but somewhere in the 180s it stops interacting with the grid. Won't draw nor will feed back. When the voltage goes up and stays up then the inverter interacts with the grid.

The inverters are built to match grid conditions

I can set the inverter into a default mode, in which it will keep on matching the grid voltage as it drops. But do I want this? Current will go up and any voltage sensitive equipment in my house will end up in territory it doesn't like.

Anyway, maybe the inverter is doing what it is supposed to. Maybe you can override that behaviour, but with risk.

@Bobster. The basic behavior of the inverters is 100% consistent with the paper user manual.

Export to the power grid is very similar to the USb mode (see 01 Output source priority) - in this mode, the inverter operates in bypass mode, but adds to this grid voltage as much current from the panels as is required in the load. Thus, the voltage in the house is equal to the voltage in the power grid.

There is another parameter "03 AC input voltage range", which forces to completely disconnect from the power grid and switch to the inverter with an exact voltage value of 220V (or 230V, as in your case). That is, if I set the UPS mode, then disconnection from the power grid will occur if there is less than 170V. But if set it to APL and then the inverter will continue to maintain the connection even down to 90V.

When the export mode is enabled, the inverter stops limiting the current consumption and it begins to flow into the grid through this open bypass.

From this point of view, it seems strange why the export stops at 170V, although parameter 03 still allows supplying down to 90V to the house and, moreover, the admixture from solar panels occurs normally.

I.e. the limitation on the admixture of solar energy is simply re-enabled (I can clearly see this in the status when requesting QFLAG and QPIGS from the inverter via com-port).

This point surprises me very much, and if my vision of the inverter operation in export mode is correct, then I am inclined to think that there must be firmware or an inverter for which the limitation is not restored to a fixed value of approximately 185V-170V.

In addition, I have the impression that this threshold is adjustable and is stored in the EEPROM chip. And, with due skills, this value can be adjusted directly in the EEPROM chip or by command via the serial interface (possibly the display serial interface, but not the one that comes out on the connector on the front of panel)

Edited July 5Jul 5 by bobah1248

I can't comment on your settings or the behaviour they provoke (or should). You clearly have a different brand of inverter than I do. I'm just talking generalities

9 hours ago, bobah1248 said:

Hello everyone!

I live in a region where it is very hot in summer, and the infrastructure still leaves much to be desired.

Sounds like South Africa 😁

For the curious, just where do you live?

4 minutes ago, HennieL said:

Sounds like South Africa 😁

For the curious, just where do you live?

Central Asia, Uzbekistan

Yesterday the air temperature was +46'C 😅

And today it was cool +40'C 😉

Greetings to Tashkent!

First of all, original Voltronic MAX E 11K is the off-grid inverter, with just a minimal grid-interaction capabilities: https://voltronicpower.com/en-US/product/detail/axpert-max-e-twin-11kw
It can export some energy to the grid, but it's just a side-effect. Well, it is possible that your clones were altered by the manufacturer in a way that allows them some degree of export control but it will never be the same like having a purpose-designed machine.

Using a proper hybrid inverter would give you more options to adjust export parameters. Speaking of Voltronic, their hybrid line is InfiniSolar PLUS, another brand worth looking is Deye. IMHO, Deye should be able to answer some of your questions about operational voltage range for the grid export, as they have working customer support.

Anyway, the 170V minimum, when the inverter stops feeding into the grid, is dictated by so called grid standards aka grid codes. Every country is using one of these standards to manage their grids. And when comissioning an inverter, installer has to pick a proper national grid code from the configuration menu in order to be compliant. Most of the hybrid inverters have manual overrides too, but you can't go too much low anyway as firmware is imposing limits.

Examples from a hybrid inverter:

So, the proper solution to the export problem would be to find and use a hybrid inverter with a suitable manual override range

On 2025/07/05 at 6:43 AM, bobah1248 said:

But, I can open the inverter and "patch" its AC voltage sensors so that it thinks that the mains voltage is still normal - say, so that it sees 180V as 190V.

Does anyone have any thoughts on these unplanned inverter circuit changes? Pros, cons?

This will work, normally there is an AD converter with a voltage divider sensing the line voltage. Altering this divider you simply "decalibrate" voltage measurements. One of the side-effects will be incorrect power reporting, as the power is being calculated on the fly, via reading voltage and current. But that's not a big issue.

On 2025/07/05 at 6:43 AM, bobah1248 said:

Or does anyone have any cheap but smart ideas?

There is no silver bullet.

A) Cheap but complicated: Technically, all the grid-codes and limits are being stored in the inverters firmware. Just find someone who is able to decompile, analyze and patch a firmware for you and you are done :D

B) Propper but expensive: Get a better hybrid inverter(s).

C) Smart but not cheap: Emulate a small hydro power. Use a spinning generator coupled with a motor, simple gearbox and electronic rpm regulator. For the generator part, the easiest is to pick 380V 3-phase asynchronnous motor, designed for 1350 rpm. If you connect this motor to the grid, it starts to spin normally. But when you couple it with a second motor, that will increase rotation to roughly 1700 rpm then the asynchronnous motor becomes the generator and starts to feed the grid. More rpm, more power. No need for complicated "phase-locking" to the grid, asynchronnous generators are just super-simple. Since I see that you are using Hass.IO, you can implement precise power control using it.

Edited July 6Jul 6 by Youda

About the cooling issue and 80% vs 50% power-throttle:

Thermal derating is normal, of course. Difference between the inverters might be caused by:

• location of the internal temperature sensors

• heatsink and thermal paste

• if both inverters are paralleled, the firmware may decide to load master inverter more than slave one. Aalthough 80 vs 50 percent is too much I'd say.

Adding a water cooling sounds like a nice DYI project, but keep in mind that there's high DC voltage inside the box. One drop of water and box is done...and the operator might be done too.

In reality, water cooling just transfers heat to some other place, where the heat must be extracted from water before it is cycled back. The only cooling medium with virtually unlimited capacity is the ambient air. Therefore, if you don't have a river or swimming pool in your backyard, you will need a secondary heat exchanger and air-blower that will cool the water. Even if you plan to heat 1000L of water for showering, you will need an extra cooling loop that will take over once that 1000L becomes too hot to be used as coolant.

If you think about all the water cooling details and gotchas, it's actually much easier to fix the air ventilation. Just blow ton of ambient air directly to the inverter from bellow, collect hot air in the top and blow it out.

BTW: some of the Axperts were designed in a way that air was sucked from the top and blowed down below. That's a stupid design, because normally the air at the ceiling is way hotter than air at the floor level.

@Youda Thank you very much for your detailed answer!

Offtop:

To be honest, I chose inverters from what was on our market. In the process of choosing, it turned out that our local sellers simply resell what is illegally imported from China.

Unfortunately, we still do not have dealerships or service centers that could give an answer at least somewhat similar to yours. For example, I had to assemble a cable for connecting the BMS to the inverter myself, as well as make settings for the BMS and inverters. In general.

I think you now have an idea of the level of local sellers.

As a result, I chose between Voltronic and Deya, without the opportunity to see and compare their work in any showroom.

In the end, I managed to find a way to buy 2 inverters and a battery directly from China. However, I was only able to find copies of Voltronic at a reasonable price (but I found out later that they were copies).

Let's get back to your recommendations:

• my inverters are budget ones and they seem to have everything (including export), but this is mostly added "just in case", and not for the intended use (in principle, I discovered this myself after purchasing them)

• it turns out that judging by your picture, the best hybrid inverter looks like the inverters from Deya due to the possibility of flexible settings and responsive service

• I need to cool the inverters forcibly with a large volume of air - this is exactly how I have it now: in the room there are only protective grilles that do not allow it to heat up from sun, an industrial fan of more than 200 W is installed. To make the cooling even better - this is only removing the front protective panel of the inverters, allowing the industrial fan to blow directly on the radiators, transformers and inductors. But this creates the danger of large amounts of dust and conductive particles getting into it

• regarding liquid cooling - everything is exactly as you said: I live in a private house, I have storage tanks for hot water. In addition, water is relatively cheap here, and I can heat the pool or simply turn it into fog (using a microclimate system) - it is very hot here in the summer, low humidity and a lot of dust

  therefore, liquid cooling would allow to reduce the temperature on the radiators by approximately 2 times, compared to air (+40'C air temperature will be worse than +15'C water temperature)

  as an option, for cooling, you can assemble a heat pump that would not use liquid, it would allow you to safely heat the water in the storage to 70'C, while cooling the radiators to 35-50'C, but this is a completely different story and research

• I completely agree - properly designed and assembled equipment is a guarantee of safety for both the equipment and the home, including its residents.

  Therefore, thoughtless conversion of radiators to liquid is not acceptable (for example, to computer, which successfully works with equipment worth several thousand USD). And first of all, because the solar power plant works not only with high voltage, but also completely autonomously (without direct supervision of people, as is done with a PC)

I had to repair inverters and in the process, I discovered that the cooling in the my inverters is assembled a little strangely:

• one fan (MPPT) blows from the bottom into the inverter

• and the other two (220VAC and Battery) blow the opposite way - from the inside to down

• i.e. in fact, the air inside my inverters is looped!!!

• I added several fans, which slightly improved the overall situation, but it worked well while the air temperature was no more than +35'C

If you are interested, here is the story of my inverters and the overly high voltage of 6 kV

Edited July 6Jul 6 by bobah1248

35 minutes ago, bobah1248 said:

• I need to cool the inverters forcibly with a large volume of air - this is exactly how I have it now...

• one fan (MPPT) blows from the bottom into the inverter and the other two (220VAC and Battery) blow the opposite way - from the inside to down i.e. in fact, the air inside my inverters is looped!!!...

You could turn the two inside fans around so that they suck the cooler air from the bottom as well. If possible, you could also install another set of small computer fans in the top of the inverter housing (if there's space) or just make some vent holes in the housing and install these fans on top of the housing, and point them to suck air out of the housing and blow it up towards the ceiling. If you then install a large extractor fan in the ceiling (or in a chimney of sorts...) you could vent the hot air away from the inverters.

45 minutes ago, bobah1248 said:

• regarding liquid cooling - everything is exactly as you said: I live in a private house, I have storage tanks for hot water. In addition, water is relatively cheap here, and I can heat the pool or simply turn it into fog (using a microclimate system) - it is very hot here in the summer, low humidity and a lot of dust therefore, liquid cooling would allow to reduce the temperature on the radiators by approximately 2 times, compared to air (+40'C air temperature will be worse than +15'C water temperature) as an option, for cooling, you can assemble a heat pump that would not use liquid, it would allow you to safely heat the water in the storage to 70'C, while cooling the radiators to 35-50'C, but this is a completely different story and research...

Have you considered installing a largish Peltier pump on to the heatsink as an active cooling element. Given that you've already imported the inverters from Chine it should not be too difficult to source some Peltiers either. Here's a link to a data sheet from RS Electronics to give you some idea: https://docs.rs-online.com/b696/0900766b8001b623.pdf

Edited July 6Jul 6 by HennieL
Typo corrected

@HennieL Thank you for suggestions.

Regarding the direction of the blowing of the built-in fans - I have installed separators inside the case for now and broken the closed loop, additionally installed a computer fan to blow air out of the inverter from the top.

But, as it turned out, computer fans are too weak - their power is less than 200 mA (at 12 V). I found more powerful fans of a suitable size on Aliexpress, with a power of 1-2 A (at 12 V).

And bought one to try, but it turned out that they have a power of only 0.8 A (at 12 V), although according to the anemometer, the air flow is about 1.5 times more powerful than the computer one.

In general, I see 3 options at once - either liquid cooling, or make holes in the inverter and add dust protection and additional fans, or buy the right inverters ;)

Regarding the Peltier elements - I have them and I even tried to play with them (air and liquid cooling). But their value is, to put it mildly, exaggerated.

Let's do some calculations:

• I measured the efficiency of the inverters, and it is about 75-80%, which is not bad in general

• Each inverter in hot weather can receive about 6 kW from solar panels, and give out 4.8 kW to the grid (at 80% efficiency)

• Thus, each inverter converts 6 kW minus 4.8 kW is 1.2 kW of energy into heat. Moreover, these 1.2 kW have 100% efficiency

• I have 2 inverters, which means I have a powerful electric grill with a total power of 2.4 kW 😂😂😂

• Each Peltier element consumes about 1.5 A, which means its power is only about 18 W

• Thus, to remove 2.4 kW of heat, we need to spend about the same power

• Then 2.4 kW divided by 18 W, we get that we need at least 133 Peltier elements, provided that they are 100% efficient, which is not the case (or at least 66 for each inverter)

• It is simply impossible to install so many elements directly into each inverter 🥲

But, of course, the idea was good - it is similar to idea @Beat installing an air conditioner, which will try to spend about 3 kW of electricity to get rid of 2.4 kW of heat.

It is for this reason that I had an idea about heating water for household needs - i.e. I would spend these free 2.4 kWh of heat on what I am already forced to spend every day 😀

Edited July 6Jul 6 by bobah1248

@bobah1248 I hear you... but look at it from another angle - you just want to keep the inverters from throttling down, thus keep their power elements below about 60-65 degrees C. If they are currently heating up to 70-75 degrees C during the day, then you just need to cool them down by 10-15 degrees, and the current cooling down systems (heat sinks, built-in fans, additional fans, etc. etc. should take care of the rest.

Have a look at this thread: https://powerforum.co.za/topic/29611-cooling-sunsynk-5kw/

6 hours ago, bobah1248 said:

1. Each inverter in hot weather can receive about 6 kW from solar panels, and give out 4.8 kW to the grid (at 80% efficiency)

2. Thus, each inverter converts 6 kW minus 4.8 kW is 1.2 kW of energy into heat. Moreover, these 1.2 kW have 100% efficiency

3. I have 2 inverters, which means I have a powerful electric grill with a total power of 2.4 kW

I think your calculation is wrong. Even if your inverters were as bad as only 80% efficient, 20% of 4.8kW would be 960W. Did you measure the 6kW from the panels or do you take the panels spec? If they really deliver 6kW the sold goes into the batteries. But I reserve measuring errors. There is no way an inverter of your size produces 1.2kW heat loss. It would very rapidly go up in flames. It's the power of our infrared room heaters.

From your writing I conclude that your inverters are Voltronic rebrand or Voltronic clones. Their efficiency is better than 90% as claimed by the specs of my Axperts.

Edited July 6Jul 6 by Beat

On 2025/07/05 at 7:40 PM, bobah1248 said:

And I'm interested in whether there is a problem with export in other inverters (including original ones).

The answer to this question could rather be given by someone who is familiar with the firmware from the inside, like @Coulomb

Unfortunately, I've never come across the part of the firmware that deals with exporting power. And since my own older inverters don't have this capability (at least they're not designed to), I have little incentive to research it. I've had a few quick goes at finding it, with little success.

@HennieL Thank you very much for the link.

As I wrote above, I installed a powerful industrial fan that ventilates the air well (sucks in from outside the house). Since my inverters have radiators inside, I additionally installed a computer fan on the problem inverter so that it would forcibly remove air from the inside. And yes, it works, but for now the outside air temperature is below 35'C. But now the outside air temperature in the shade is on average 42'C and this continues every year for about 60 days.

I think I just need to put up with these abnormal two months (the first one already left) and not overheat the inverters because of electricity export. Especially since the components for repairing inverters are very expensive (and if the electrolytic capacitors will dry out due to the overheating, then they will have to be ordered from China or Russia, and wait for delivery for about a month)

@Beat Unfortunately, my percentage calculations are correct. Although the accuracy of measuring the electrical characteristics of inverters leaves much to be desired, the inverter shows exactly 80% efficiency when reading data via the serial interface. I also correctly calculated 20% from 6 kW (from the input power), and not from the 4.8 kW (where the efficiency has already been recalculated).

Regarding the declared efficiency of inverters by the manufacturer, you most likely saw the "Peak Efficienty" parameter.

That's right - in ideal conditions (for my inverter, air temperature 20-25'C, humidity 30-80%, voltage at the MPPT input 380VDC, resistive load that not more than 80% of maximal power inverter), inverters are really capable of delivering an efficiency of up to 93% and may be even for several minutes.

But as soon as the voltage on the MPPT drops, the temperature on the transistors and inductors rises, and the efficiency begins to fall rapidly. And at this point, you need to focus on the "Rated Efficienty" parameter, which is not declared by all manufacturers (too many dependencies, even the region of usage affects the efficiency)

In any case, "Rated Efficienty" usually does not fall below 75% (again, in ideal conditions for air) and this is taking into account the full chain of DC-AC conversion.

Anyway, thanks for your thoughts and calculations.

Edited July 7Jul 7 by bobah1248

@Coulomb Thank you very much for your feedback.

In fact, I was only worried about one thing: let's say I change the voltage measurement characteristics at the AC input to +10V. Then I turn on the export, the inverter will close the bypass. And then the inverter will see that at the AC input, say, 190V (real 180V + 10V my virtual bonus), and the inverter AC output sees the real 180V.

If I were the inverter, I would be confused, then decide that the inverter is faulty and refuse to work. The same applies to the internal high-voltage HVBUS bus, from which the "sine wave drawing" occurs, as well as battery charging/disharging.

That is, I think it may not be enough to simply change the resistors at the AC input - I also will have to change resistors at the AC output, then possibly on HVBUS, and this in turn will require redoing the same on the MPPT sensors and possibly even the battery charger.

In principle, it was this chain of probable events that made me write my question on this forum.

It is possible that I am simply exaggerating and the firmware in my inverter does not care about the listed inconsistencies.

But, since you have never encountered anything like this, I will have to be extremely careful if I decide to do such a rework sometime in the future.

Thanks a lot!

Edited July 7Jul 7 by bobah1248

1 hour ago, bobah1248 said:

That is, I think it may not be enough to simply change the resistors at the AC input - I also will have to change resistors at the AC output, then possibly on HVBUS, and this in turn will require redoing the same on the MPPT sensors and possibly even the battery charger.

Input ADC yes

Output ADC yes

HVBUS ADC no

I doubt that there will be fixed voltage ratio of HVBUS to Output that is checked. IMHO, these inverters just measure the output and then loopback. Since the output voltage depends on the loads too, loopback and PWM duty cycle will be used to adjust voltage on the fly.

Shifting about 10V down should be feasible.

1 hour ago, bobah1248 said:

It is possible that I am simply exaggerating and the firmware in my inverter does not care about the listed inconsistencies.

Most of the times, there's a relay between output of the inverter and the grid.

• Inverter matches the grid frequency and phase by shifting PWM timing.

• Then it matches the voltage by altering duty cycle.

• Finaly, when all of this is matched, it closes the relay.

• The above is nicely visible on a dual-channel scope.

For the export of active power to happen, inverter increases its output voltage a few volts above the grid voltage, while keeping the phase and frequency locked. This forces the energy to flow back to the grid.

PS: On top of that, proper hybrids have an option to change phase angle between the current and voltage, which results in injection of some amount of apparent power to the grid. Sometimes, grid operators demands this function to be available via remote control of large PV installations, as they use it for grid compensation.

2 hours ago, bobah1248 said:

@HennieL I think I just need to put up with these abnormal two months (the first one already left) and not overheat the inverters because of electricity export. Especially since the components for repairing inverters are very expensive (and if the electrolytic capacitors will dry out due to the overheating, then they will have to be ordered from China or Russia, and wait for delivery for about a month)

Yes, that would be the simplest, and best (IMHO) solution. One can choose to boost a car's engine to deliver nearly double the horsepower it was designed for, but then the engine just won't last. Even without modifying the engine, it would still not last very long if you continuously kept the revs on the red line - I know... did just that in my younger days with an old motorbike after drinking too much rum 🫠☠️

So, throttle back on your power export when conditions require, and your inverters will last much longer.

Just one note to add: the root cause of why there is no 220V on the grid during the day is that other people are drawing too much current from the grid and the power line to the utility transformer is too long and thin. This causes voltage drop due to line resistance.

The fact that ppl are using voltage stabilisers makes this even worse, as the stabiliser is just pulling even higher current from the line, in order to make a proper voltage (technically being auto-transformer with a servo).

The propper fix is:

• to improve quality of the cable between you and the transformer,

• or make it shorter,

• or getting your own powerline from the same transformer.

...but I am sure that none of the above are manageable...

Edited July 7Jul 7 by Youda