Tigo Optimiser Recall?
At the time, Tigo optimisers seemed like a good idea. I’ve even spruiked Tigo as an affordable shade solution in a past review. But my recent Tigo testing has uncovered two major issues that render Tigo optimisers worse than an empty black box. In this Tigo optimiser review, I’ll explain why many, if not most Tigo optimisers may need to be recalled in order to update the firmware.
But, before I explain to you why I think Tigo should recall and upgrade many of the optimisers sold over the last few years, I’m going to explain three different situations where Tigos are commonly used. Not all of them are clever.
- The first shade scenario where Tigo’s make the system work worse. That’s right, even if they are operating correctly, Tigo optimisers can drag down the performance of a solar system.
- The second shade scenario, just to soften the blow, I’ll show you a shade situation where Tigo optimisers make a solar system work a bit better.
- The third example I’ll give is where functioning Optimisers (or microinverters) are absolutely essential.
However, that will lead me to the huge problem I’ve found with Tigo optimisers. And you’ll see why in this review I insist Tigo should recall and upgrade the firmware of many of their optimisers sold over the last few years. If you want to cut to the chase and read about the issue that floored me, click here. (if you’re reading this on a phone, you’ll need to scroll down a little further after clicking)
Tigo Drags down the performance of a solar panel
First, let’s look at the example where a correctly functioning Tigo can drag down the performance of a solar system. Have a look at these two examples. One has Tigo optimisers installed, the other doesn’t. Let’s say each panel is operating at 300w and at that time of day there is going to be shade on part of the solar panel.
A Standard String System
Looking at the system without optimisers first. Will the string be dragged down because of shade? No. Despite what you have been told, quality modern string inverters are much smarter than that. Instead, the bypass diode will engage on that cell string and the panel will run at 200W. It blows my mind that people in the solar industry still don’t seem to understand the simple function of a bypass diode and quality string inverter.
A Tigo String System
Now let’s put on Tigo optimisers and see what happens. The good thing about Tigo, is that it treats the panel gently. Each panel only has to handle the power and voltage of just that one panel. Which means that when there is shade, the panel isn’t in danger of being damaged by the hot spots that are normally created when a panel is shaded. Because the panel is not in danger; the bypass diode does not engage. But because the bypass diode doesn’t engage, in this specific type of shade, the whole panel will be dragged down, and it will work at around 20 or 30 watts.
If you want a deeper dive into why this happens, check out this Enphase video. Tigo works pretty much the same as Enphase. My point is that the addition of Tigo to a string system can sometimes make that system perform worse.
Tigo’s advantage with split cell panels
But Tigo doesn’t always drag down a panel’s performance. Let’s turn things positive for a bit and show off Tigo in its element: Tigo optimisers on a split cell panel with top or bottom shade. Check out this example.
We’ll start with the unoptimised system. Again, let’s say each panel is running at 300 W. If you shade 4 panels on the unoptimised system, the 4 panels will be bypassed. The system will then run at 5x 300 watts, or 1.5kW.
Now we’ll look at the same shade situation, except with Tigo optimisers attached to each panel. Because each optimiser can operate at its own current value, then it can choose the 4 half panels, running at 150watts, and the 5 unshaded panels. Tigo outperforms the unoptimised system by 600 watts.
Optimisers and micro-inverters work really well on split cell panels when the entire width has partial shade.
If you want to understand why optimisers allow the top half of the split cell panel to keep running, watch my video on Enphase with split cell panels. Again, Tigo responds the same way as Enphase on split cell panels.
Tigo in Complex shade
Now let’s mix it up. Let’s say the shade falls on three panels, but two of the panels are only shaded across one cell string.
First on a Tigo system the middle panel will operate at 150 watts. That’s the benefit of a split cell panel and an optimiser.
Next, look at the left-hand panel. Because an optimiser is installed, the bypass diode often doesn’t engage. So the entire panel may be dragged down to about 30 watts. This doesn’t always happen – but happened multiple times when I was testing it using different string lengths and different inverters.
And the right panel may work at around the same as the left one, or a bit less. Lets say 20 watts. So the three panels give us a total of 200 watts.
The unoptimised system with complex shade
Now let’s look at the same system without the Tigo optimisers.
The middle panel will be bypassed which means it will run at 0 watts. Bugger.
But because we don’t have an optimizer installed, the left panel will bypass the right side cell string in order to protect the cells from hot spot damage. A happy result of that string being bypassed is that it won’t drag the rest of the panel down, so it will run at about 200 watts.
The right panel will bypass 2 cell strings which results in that panel operating at about 100 watts.
So, in this case, at this particular time of day, with this amount of shade on a split cell panel, you’d often produce more without Tigo optimisers.
It’s pretty complicated, isn’t it! Not just as simple as whack a Tigo on and all your shade problems will be solved.
Tigo on split orientations
Let’s move on and look at a situation where Tigo optimisers (or microinverters) are essential. When you have a single string of panels split across multiple orientations, you must install optimisers. This is not only required by Australian standards, but if you don’t do this, your solar will perform miserably.
I’m going to start off with the basics, and I’ll explain why this layout absolutely needs optimisers or microinverters. If you already know why, skip ahead to the next heading.
Let’s install 12 panels without optimisers (see image below). At 9 am in the morning, let’s say the northern panels see fairly decent sunlight so they want to run at 180 watts each. 180 watts would be made up of 30 volts and 6 amps of current. 30 volts times 6 amps equals 180watts.
But the panels on the west are facing away from the sun, so they only want to run at 90 watts. That would still be about 30 volts, but only 3 amps of current.
Note, solar panels typically run at approximately the same voltage all day, usually about 30 volts. The current is the figure that changes throughout the day.
As mentioned earlier, these panels are connected in series, so if you understand current (as in amps), then you would have already seen the problem.
A Kink in the garden hose
Think of a series string as all the power from the 12 panels running through the same garden hose. The “kink in the garden hose” theory doesn’t always apply to solar panels, but in split orientations, it does.
Think of the current (or, the 6 amps and 3 amps) as the amount of water running through that hose. How much water is coming out the end of the hose at 9 o’clock in the morning? 6 amps or 3 amps?
The problem is, it can’t be both.
The panels on the west, running at 3 amps, acts as a kink in the hose, so only 3 amps can run through the whole string. This means every panel will only work at 3 amps and 30 volts, or 90 watts. We’ve just lost a heap of energy from the northern panels.
Solving the kink with Tigo optimisers
Fixing this problem is the job of any optimiser or microinverter. So let’s install Tigo optimisers on every panel and see how it works.
The panels on the west will still only work at 90 watts. Optimisers don’t magically create energy. The Tigo receives that 90 watts as 30 volts and 3 amps. Power equals voltage times current.
The optimisers job is to increase that current to 6 amps, so the other panels are not restricted. Again the Tigo optimiser doesn’t magically create current. Instead, it increases the current by reducing the voltage.
It reduces the voltage (or bucks the voltage) to 15 volts. To balance the equation, it uses grade 5 maths. It increases the current to a value of …. have you worked it out? … 6 amps.
15 volts x 6 amps is still just 90 watts. So we haven’t magically increased the power production of that panel. We’ve just made it work at the same 6 amps of current as the rest of the panels in the string. Now the northern panels can run at 6 amps and, 30 volts, which equals 180 watts.
Now that you know how it’s supposed to work, let’s see how it worked in reality. Let’s see what went wrong and why I am pushing for a massive Tigo product recall, or product upgrade.
Here’s my test.
Why Tigo optimisers should be recalled
So the curveball in this blog is thanks to my good mate and solar industry legend, Jack Longy Long. Jack called me earlier this year to talk about a Tigo installation installed by a fellow Solar Cutter. The Tigo optimisers were installed on a single string of panels, across different orientations. The Tigos were clearly not doing their job. He knew I was in the middle of Tigo tests, so he asked me to simulate his problem to help a fellow cutter. He was definitely on to something, but it took me another 6 weeks to work out exactly what that was.
I set up two systems of 19 panels each on 2 Fronius inverters. 5 panels north and 12 panels west. On one of the systems, I put optimisers on seven panels. 5 northern panels and 2 Western panels. I connected these panels in series, on one input of the inverter. Dealing with this split orientation should be a piece of cake for Tigo.
The other 10 panels went on the other input of the Fronius inverter.
On the second system, we just wired it the way it has to be. 5 panels on one string and 12 on the other. I monitored both inverters with solar analytics.
It turns out that my mate Jack was right. The Tigo system worked pathetically – as if no optimisers were installed at all. In the morning, the panels that were facing west dragged down the northern panels. In the late afternoon, the western panels were dragged down by the northern panels “It was as if there were no Tigo optimisers installed at all.”
To find out what was going on, I connected the Tigo optimisers to the Tigo monitoring platform. We had a few rainy days between testing but when the sun came back out, suddenly the system was working correctly. It didn’t make sense. Not knowing how to simulate the problem again, I switched out the optimisers for new ones. This time it worked even worse than the first test.
Tigo optimisers need initiating
After a lot of head-scratching, and with Tigo’s help, we worked the problem. The optimiser firmware needed upgrading. Tigo claimed they had a problem with a particular batch of optimisers with a specific hardware version coming out of the Philippines. The optimisers were programmed wrong. They would only start working as optimisers after they were connected to the internet.
Did you get that? The $75 selectively deployed Tigo optimiser won’t work unless you connect it to their $800 monitoring hardware. That’s a problem. But how big is this problem? Is it limited to just one hardware version that came out of one factory as Tigo suggested, or should there be a Tigo optimiser recall issued?
How widespread is Tigo’s issue?
I tried the same test with another hardware version – but still from the same factory. No luck. Far out. I had the same problem. The optimiser didn’t work until I connected it to Tigo’s monitoring hardware. So I called around and found a supplier with a third hardware version. Again, the same problem. At this stage, all of my optimisers had been manufactured in the Philipines, albeit purchased 18 months apart. Tigo suggested I try an optimiser from their Chinese factory.
I called around distributers and found an optimiser that came from Tigo’s Chinese factory. Our supplier delivered two in an uber. I installed them straight on the roof and waited for the results. Bugger. Tigo’s theory was wrong. It’s much worse than they thought. I’ve now tested Tigo optimisers from the factory in the Philippines and the factory in China, including 4 different hardware versions. None of them work, unless you connect them to Tigo’s online monitoring.
How Far Back Does the Tigo Issue Go?
I then started looking at Fronius monitoring from systems we had installed with Tigos back in 2019. We found multiple sites where the Tigo optimisers were not working, and we found remarkable improvements when we updated the firmware.
What is the extent of this problem? I think it’s highly likely that every Tigo optimiser that has been installed in the last few years, without the expensive Tigo monitoring hardware, have serious firmware issues. Unfortunately, it’s not as simple as calling the Tigo an empty black box that does nothing. Our testing has shown occasionally the Tigo works and improves performance, sometimes it does nothing, and sometimes it severely drags down performance. The problem is intermittent and it’s difficult to identify. The Tigo optimisers with the faulty firmware will keep playing up until someone temporarily installs the Tigo gateway hardware, and connects the optimisers to the internet to update the firmware.
Tigo Issue Diagnosis
How do you find out if the optimisers you installed are the faulty ones? If you’re clever, you can look deeply into the inverter monitoring platform, and make an educated guess if the current should be higher or lower than it shows. A telltale sign is the voltage and current graphs saw toothing, showing the intermittent nature of the issue. If you identify an issue, drive to site, connect the optimisers to Tigo cloud connect, and see if the current value in the inverter monitoring platform increases on an average day. We’re working on a way to identify the issue while on-site before we upgrade it. But the intermittent nature of the Tigo fault mixed with the dynamic nature of string inverter solar systems is making that difficult.
I’ve spent more time on these Tigo tests than any solar product test I have done before. I’ve given Tigo ample evidence and had almost got to the point where they sent out multiple Tigo “Cloud Connect” devices to fix this issue. But then Tigo changed their mind. They are now saying they don’t believe it is a widespread problem because they haven’t seen the issue anywhere else.
Seriously, Tigo. If you don’t have eyes, how do you expect to see? Without Tigo’s monitoring in place, there is no clear visibility to see the issue. If Tigo receives a complaint where an installer recognises an issue, then Tigo will request the system is temporarily connected to “Tigo Cloud Connect” to see what the issue is. On connection to “Tigo Cloud Connect”, the Tigo firmware is updated. Tigo can then “prove” that there is no issue with their monitoring. The installer is left confused and moves on to the next stitch-up. Tigo comes off looking like the good guy.
Fully functioning Tigo optimisers are not necessarily beneficial in shade situations. A little bit of shade on one panel can drag the whole panel down. If you didn’t have Tigo installed, that panel would have used the bypass diode to bypass the shaded portion of the panel, resulting in higher production.
Tigo optimisers can work well with a particular type of shade on split cells panels, and they are also necessary if you have panels on the same string in multiple orientations.
However, my tests in the office, and in the field have shown that multiple batches of Tigo optimisers are not working. I’ve identified faulty Tigo optimisers from 4 different hardware versions that we purchased between January 2020 and July 2021. We’ve also tediously analyzed and rectified faulty optimisers from several installs that we did back in 2019. The solution is the optimisers need to be connected to the internet in order for them to start working. This involves about $800 worth of hardware being installed and left on the premises overnight. Tigo so far have been extremely difficult to deal with, leaving the burden of proof for each installation in our court.