4 hours ago, Darknight said:

Thanks. I was just wondering if it was possible. I agree with you that 6 panels would be pushing it too much. I do have another 40amp mppt controller sitting in a box at home which I intend to use for another inverter to power a part of my house that couldn't be powered by my 3kv. For interests sake, how does it work to have 2 mppt controllers on a single inverter. I didn't think that was possible or necessary.

 

Thanks for explaining everything for me. I think I'll stop at 4 panels. I need to have the 4th panel so that I can make use of the 3rd panel which I already own and is not currently connected. Also, so that I can have enough power available from the panels to charge the battery and feed the load sufficiently.

im no expert by any means, but basically it would be connected in parallel, and it would only achieve charging the batteries faster, so the batteries would receive a similar current from both chargers, but double the amps (or more than one chargers current anyway). In practise i have never done this, only heard that plenty people do this, particularly useful when you have arrays facing different directions.

On 2019/10/30 at 1:25 AM, Dex_ said:

but basically it would be connected in parallel...

"It" here being the second string of 2 panels in series, not one individual panel. Just to be totally clear.

3 hours ago, Coulomb said:

"It" here being the second string of 2 panels in series, not one individual panel. Just to be totally clear.

Does that mean that the second string of 2 panels in series would be wired into the standalone mppt directly? Does the standalone mppt connect to the inverter? If so, in what way? I'm just trying to wrap my head around this. Sounds super interesting.

You would connect the other MPPT onto the batteries, the inverter pulls power from the batteries.

6 hours ago, Coulomb said:

"It" here being the second string of 2 panels in series, not one individual panel. Just to be totally clear.

sorry i should have been more clear, i was referring to the controller here.

5 hours ago, Darknight said:

wired into the standalone mppt directly?

Sorry. I forgot there was even mention of an external solar charge controller (MPPT or otherwise). I was envisaging a single box with an inverter and charger combined, and capable of handling more power than a single string of panels could provide. In these cases, you add extra panels by paralleling other strings.

Perhaps some confusion arises because the most common form of inverter, the grid-tie inverter, typically has a high voltage SCC, and you usually add panels by adding them in series, with a definite maximum number, and a definite lower number as well. Occasionally, even with this type of inverter, you might be able to add a second string in parallel with the first, or sometimes they have a second solar charge controller built in, so that it's designed for two independent strings.

I hope that doesn't make things even more confusing.

So just another quick update. I found a spec sheet for my inverter which specifies that the max PV power array is 1500W. This means if I add one more 330W panel to bring my total number of panels to 4, I should fall within the acceptable range. However, there is a new wrinkle which I need a bit of help on.

The company I bought my 3 x 330w panels from had run out of stock of the 330w panels. They do however have the 335w panel from the same manufacturer and same panel model. The 3 panels I already have are the Canadian Solar 330W HiKu panels. The 335W panel that my supplier has in stock is Canadian Solar 335W HiKu panels. Below is a picture of the spec sheet for the panels. So my plan is to have 2 pairs of series wired panels in which both pairs will be wired together in parallel. Would I still be able to do that if the one pair of series wired panels consists of one 330W panel and one 335W panel? I've read that in the case of using mixed panels, the system will use the lowest rated panels output which I'm fine with since the difference in output between the two panels is quite unsubstantial.

 

imo that will work just fine

I did almost the same in adding a 255W Yingli panel to a string of 6x250W. That worked fine but the physical size is just different enough to irritate my sense of aesthetics.

2 hours ago, GreenFields said:

I did almost the same in adding a 255W Yingli panel to a string of 6x250W. That worked fine but the physical size is just different enough to irritate my sense of aesthetics.

I understand this 150%. I'm currently looking at getting a custom-fabricated mounting rack for my panels because the one my installer provided is a piece of aesthetic crap.

3 hours ago, Dex_ said:

imo that will work just fine

Awesome!

On 2019/10/22 at 3:47 PM, Darknight said:

I'm all the way in Zim. The panels I have are the HiKu panels with the line divider in the middle of the panel. How much are you selling yours for?

I am in Zim and supply the HiKu panels all sizes. Please shout if you still need a panel and some help

So, Just an update on my solar installation.

In short, it's messed up. I've tried everything I could think of but it doesn't look like it's working properly. I've resigned myself to just living with it since I've already sunk money into it and the only way I could recoup my money is to sell what I have.

I've put 4 panels (3 x 330w, 1 x 335w). The panels are wired in a series-parallel configuration. My inverter is now doing the same thing it was doing when I had just 3 panels wired in parallel. I've got the monitoring software for the inverter and from the depressing information I can see, the only conclusion is that the solar inverter I have, does not like solar energy. I've spoken with the manufacturers directly but they keep telling me everything is okay and the inverter is working "as it should". The reason I don't believe them is because I have 1320w (I know I'll never generate the full 1320w of power from the panels) of solar panels to power a load of 800w at max and yet, on a warm day, with minimal cloud cover, my batteries are never charged fully since they are frequently being used to power my load when my inverter decides not to draw any solar energy from my panels. This happens frequently during the day. On my monitoring graph's for these days, there are frequently periods of between 10 - 45 mins where my inverter is not drawing on any solar energy.

Anyway, thanks for all the help you guys provided. I just made the wrong choices when it came to purchasing my inverter.

 

 

Do you mind posting the graphs/info that your monitoring software is displaying?

 

1 hour ago, Darknight said:

On my monitoring graph's for these days, there are frequently periods of between 10 - 45 mins where my inverter is not drawing on any solar energy.

That sounds so much like the PV "dips" that the latest Axperts seem to be plagued with; see the Axpert - strange behaviour (potential MPPT issue) topic. But this is a Growatt inverter, correct? My theory has been that Growatt have models that although the Growatts have remarkably similar specifications to Axperts, they had long ago split off their own firmware. Here it looks like they're being bug compatible 😐. Or copied the bug somehow.

19 minutes ago, Coulomb said:

But this is a Growatt inverter, correct?

Correct

20 minutes ago, Coulomb said:

...they had long ago split off their own firmware.

Speaking of firmware, the Growatt technician I was speaking to sent me an "updated" firmware along with the software and steps to push the firmware update to the inverter. I did the update without any issues. The technician said that I needed to factory reset the inverter after the update, which I also did. When I contacted him to tell him that the inverter behavior hadn't changed, he told me it was because I didn't factory reset. I told him that I did and I haven't heard back from him since then.

29 minutes ago, Coulomb said:

Here it looks like they're being bug compatible 😐. Or copied the bug somehow.

I initially went to the company I had bought the inverter from and told them what was happening. I even showed them a video of the inverter screen. They told me that it was an issue they had experienced before and that it was due to an issue with the MPPT. They then sent their own technician to check the inverter but he didn't even check it. He told me that this inverter has a max solar input wattage of 1000w and that because I had more than 1000w, that's why I was having this problem. I contacted the Growatt people to find out from them what the correct max solar input wattage was for my inverter. They told me 1500w. The Growatt tech also said that as long as the voc of the solar panel array is less than 102v, the inverter will operate fine regardless of the size of the solar array.

5 hours ago, francois said:

Do you mind posting the graphs/info that your monitoring software is displaying?

Sure. Below are the charts from 2 days this month when the weather was sunny with slight cloud cover. I also have a video of what is happening on the inverter screen if you want to check that out too.

So, I've been speaking to the Growatt technician in China and he is basically sticking to his guns that the inverter is working normally. He sent the following explanation;

it's a battery protection mechanism，

when battery is charged，battery SOC will go up to 100% finally，battery will send an order to PV charger to shut down，stop charging，avoid charging battery too much and damage battery，

after a while using，if battery SOC drop below 95%，PV charger will start working automatically again to supply power to the load and charge battery until it's charged 100% fully again，

in this way，if there is main grid outage，battery will always keep almost full，

suggest use SBU mode in program 01 setting，it will use more power from battery，

I might be wrong but doesn't constantly charging and discharging a battery reduce the lifespan of the battery? Or am I understanding this incorrectly?

 

 

1 hour ago, Darknight said:

doesn't constantly charging and discharging a battery reduce the lifespan of the battery?

Small discharges and recharges are nowhere as significant for battery life as large discharges. So that's not going to affect life dramatically.

Maybe what is happening is that the inverter interprets the signal from the BMS as "no PV power at all" rather than "no more power than the load needs". Is setting 22 (according to my downloaded manual, "Solar balance enable") enabled (SbE)? It is on by default, but if it turned off for some reason, that could explain the behaviour.