Good day forum members,

This articles hits the nail square on the head as i have seen many mismatched solar arrays to mppt's power ratios causing damage to the inverters. Also cheap non standard( not Staubli) mc4 connectors causing hotspots at terminations. The cracks are showing where non compliant installations was done during peak load shedding season. My advice, should you have any doubts to the standard of your installation get i checked out by competent solar operators/master electricians.

https://www.suidkaapforum.com/News/Article/Property/mismatched-solar-components-costing-sa-homeowners-thousands-202502040946

I'm confused. I thought the MPPTs only drew as much as they needed. 

Or as it that they draw as many WATTS as they need, but the current could still be too high? Which is why it is necessary to pay attention to serial & parallel connectiond between panels.

Cheap connectors I understand. 

8 minutes ago, Bobster. said:

I'm confused. I thought the MPPTs only drew as much as they needed. 

Or as it that they draw as many WATTS as they need, but the current could still be too high? Which is why it is necessary to pay attention to serial & parallel connectiond between panels.

Cheap connectors I understand. 

My thought is slightly similar so, stand to be corrected. Let me use the analogy of a dam full of water: The water is your Pv and the Dam wall is your MPPT/MPPTs if there's more than one. If max VoC of inverter is exceeded the MPPTs capacity to hold back current will be compromised and hence the MPPTs will be damaged or the other parts of the inverter system, hence @TaliaB's recommendations to ensure quality workmanship and quality parts (MC-4) connectors. The water in the dam will push against the dam wall and the MPPT will always draw as much as it requires but undue force will result in disastrous consequences.

Hi hope I don't qualify as a "bakkie-brigader" however, I think this article may have a good intention but the explanation is a bit inaccurate. 

I have seen this arguement being had a lot and once again it's a little lack of what is the actual risk. What is risky here ? The MPPTs are a DC driven device. It extracts power by the product of Voltage and Amps. What is the limitation to observe the Volts or the amps and what happens to either if you exceed them??

The MPPT will have a 500V max voltage for example. If you go and connect enough panels in series like 10 in series at 52V per panel (520V) you will exceed the raw voltage input & the MPPT can be damaged.

Let's say there is a amperage total expressed as 11A on the MPPT. What happens if I use a 550W JA Mono panel rated at 52V per panel Voc and Imp at 14A. What will happen to a string length of 8 panels??

A lot of ppl and probably the author of that article believes that we ok in the Voltage range because 52V x 8panels = 416V total. So voltage is GOOD. What about the current? They believe the MPPt will blow and get damaged because the panels at Max power current will deliver 14A and fry the MPPT. This is grossly incorrect!! The MPPT will drink 11A from the panels because that's all it needs. It won't kill itself trying to get drunk. 

If someone including this author feels anything differently let's try to compare logic if not science. You have a 5kWh or 100ah battery attached to this same inverter. It's rated battery max input current draw is 100A. If I attached another 5kWh (100ah) battery to this is parallel what will happen?? Everyone knows the inverter doesn't blow up. However if you connect them in series to get 100V you have a problem and will damage the inverter. 

Some ppl mock the humble Bakkie Brigader, however, there are some basic fundamentals that need to be understood before we point fingers. 

Now we can argue further that there will be losses with the 550W panel because it will never reach full rated power and I agree with that. The 460W panel is a better fit because it has 11A Imp rating. But let's just say the message to pass on is that poorly integrated equipment can cause damage and losses in production but the fear mongering of ppl saying the amps will damage the MPPTs is just a camp fire story. 

Sorry to be a pain but even an electrical engineer at a Multi million rand project wanted me to connect an Atess inverter at 1100V. The max MPPT voltage is 1000V and the MPPT range is 450V to 800V. I was carrying out the commissioning & I refused. So the moral of this story is that Solar is a relatively new technology and a lot of operators/ installers/ electrical engineers/ Bakkie Brigaders and plumbers know what they are doing and a lot don't know. I couldn't care less the title of the person, we don't all know the same things neither do we have the same experience levels.

Edited February 8, 20251 yr by Steve87

@Steve87

You driving a single or double cab?😜

Roofrack or canopy?🤣

As someone once explained to me  You have a 40A mains CB.  Does your 8A Air Fryer blow when you switch it on?

15 hours ago, Virwat said:

@Steve87

You driving a single or double cab?😜

Roofrack or canopy?🤣

I think @Steve87 is, at least in part, defending the smaller companies. I have seen a few articles in local papers that seem to be saying "deal with the big companies. They have the expertise." I don't think it is beyond the realms of possibility that there may be collusion to plant such stories, or that the journalist writing the report has phoned some big company - they're easier to find - and asked one of their managers for some input. And so that manager is quick to point out that you shouldn't deal with those small businesses because you don't know what they don't know. And since the name of his company has already been mentioned ("We asked the chief technical officer of SuperSolarBob...") this helps his business in particular and big companies in general. 

But it is not the case that a smaller company doesn't have standards and expertise. Anybody who has dealt with Steve will know that he has both, that's why he's one of the highest ranked and most appreciated contributors to this forum.

Edited February 9, 20251 yr by Bobster.
spellling and klarity

21 hours ago, Steve87 said:

If someone including this author feels anything differently let's try to compare logic if not science. You have a 5kWh or 100ah battery attached to this same inverter. It's rated battery max input current draw is 100A. If I attached another 5kWh (100ah) battery to this is parallel what will happen?? Everyone knows the inverter doesn't blow up. However if you connect them in series to get 100V you have a problem and will damage the inverter. 

Hear that? That's the sound of a penny dropping.

Thanks Steve for explaining the blindingly obvious.

What some people don't realize (know) is that most (if not all) of the inverters MPPT's design has a safety factor of x% on top of the allowed Amps.

i.e max input is 20A, but the design max is maybe 28A.

That's why Sunsynk as an example can up/down the max. by simply altering the Firmware.

9 minutes ago, Virwat said:

What some people don't realize (know) is that most (if not all) of the inverters MPPT's design has a safety factor of x% on top of the allowed Amps.

i.e max input is 20A, but the design max is maybe 28A.

That's why Sunsynk as an example can up/down the max. by simply altering the Firmware.

Okay but does that mean that you can have 50A on a mppt and it will be fine?

 

Because if they can set it to only draw 20A,25A or 28A?

 

You can give a inverter 500Ah battery but a 5kw inverter will be fine just drawing 100ah max

 

 

Edited February 9, 20251 yr by Stefan Cornelissen

3 hours ago, Virwat said:

What some people don't realize (know) is that most (if not all) of the inverters MPPT's design has a safety factor of x% on top of the allowed Amps.

i.e max input is 20A, but the design max is maybe 28A.

That's why Sunsynk as an example can up/down the max. by simply altering the Firmware.

I guess any engineered product will have a margin of safety designed in over and above the rated performance. In the case of an inverter's MPPT I'd look to the Imp rating first, which is what the IGBT's will be setting/controlling the max draw at normally - say 13A for the Deye. Next there's the Isc rating, and that's the fault current that you'd expect the device to be able to handle without being permanently damaged - 17A. And over and above that there should be an ultimate current limit at which the device will overheat and maybe burn out. What that is? 20A or 25A? No idea.

But I'm not convinced that a 545W panel with say 13.2A Imp, 13.9A Isc or thereabouts, which operates at below that current most of the time, and only really sees 13A around noon in summer, is excessively overloading a 5kW Deye. Not a fan of the idea of putting 17A panels on it though. Maybe some folks out there with this 550W panels can comment on their experiences.

Edited February 9, 20251 yr by GreenFields

One can add larger panels rated at higher amps but there will big losses. So yes it will work but the panel will never reach its rated wattage quite simply because the MPPT is not designed for such a panel. 

In the early days of Grid tie inverters they had the same issues with their 11A rated strings into the MPPT. That is one of the reasons the Solis S6 is such a good prospect for the residential market. However, one must note it's the latest addition and new comer so it definitely has to have better technology. If we had a new generation Deye 5kW it would no doubt have the wider voltage band and current specs. 

I don't see Deye or Sunsynk spending money for that it makes no sense. There are bigger fish to fry...

We must always account for temperature rise when considering the power equation for electronic equipment. Excessive over-paneling or oversizing—such that the MPPT spends five hours a day at its current limit (clipping)—will inevitably impact the overall lifespan of components within the inverter.

Temperature rise is the most significant factor affecting component longevity. In electronic product design, we should adhere to this fundamental principle:

For every 10°C increase in temperature, average reliability decreases by 50%.

The same principle applies when evaluating the charge current of LFP batteries—or any battery. If a cell is rated at 1C, consistently charging it at 1C will reduce its lifespan, as the increased internal temperature will have a far greater impact than calendar aging.
 

 

Very interesting

But I think the current capabilities will be connected to the maximum current the cabling, switchgear, transistors can handle continuously.

Same as certain equipment that starts to throttle the output due to the internal temperature rising, ie a high power flashlight which throttles the output when the temp goes rises to protect itself.