Understanding a Sunsynk inverter

**Isetech** · 01-Jul-22, 08:10 PM

Note! I am no expert in this field, what's called winging it, feel free to steer me in the right direction or correct any incorrect information.

I am busy preparing to setup and 5 kva Sunsynk inverter, which will be linked to a 5 kwh battery and a couple of panels.

Lets start with the panels selection.

Now that I know what inverter I will be using, I can choose the panels.

The Sunsynk has 2 MMPT inputs, which means I can connect 2 strings.

For now I will be only using 1 of the 2 mppt's.

How many panels can I install, I would need to look at the inverter specs

PV String Input Data

Max. DC Input Power 6500W
PV Input Voltage 370V (100V~500V)
MPPT Range 125~425V
Full Load DC Voltage Range 240~425V
Start-up Voltage 150V
PV Input Current 11A+11A
No. of MPPT Trackers 2
No. of Strings Per MPPT Tracker 1+1

What would I look at first, the current rating of the panel, if the current rating of the panel is 550 watt, 13 amps and the VOC is 40 volts. Can I use this panel for this inverter? no. Why because the current is too high for the inverter (11A).

I would have to look at a smaller panel, lets say 380 watt, 10 amps and 40 VOC. Can I use this panel? Yes, because the current is within the inverter current range.

How many panels can I link in series to create a string? The max V for the inverter is 500V, but you dont wan to go to the max so working within the MPPT range would be as better option. 425/40=10.6. It would be advisable to use 10 panels.

The max DC input is 6500 watt, 10 panels at 380 watt = 3800 watt.

IF you plan to use both MPPT's to the max, it would be better to fit 8 panels per string which would give you 3040watt X 2 = 6080 watt.

If you wanted to start out with just a couple panels, what would be the least mount of panels? 125V/40=3.125. It would be advisable to fit at least 3 panels to start with and add as the budget allows.

**Isetech** · 01-Jul-22, 08:17 PM

I am not going to worry too much about technical phrases right now, rather try keep it simple.

Now that we have selected the panels, its time to select the battery. Something else to consider before we select the battery, the total load.

How many panels would be considered enough for a system, enough to power the essential, non essential and the charge the batteries.

At a later stage we will look into an actual installation, the correct panels size and quantity required to run a site and then select the inverter and batteries to make it all work.

**Isetech** · 02-Jul-22, 07:05 AM

Some would say that we should design the system around our power demands, in reality most people cant even afford a full 5 KVA system complete with panels, inverter and battery.

What I have been trying to do, is find a solution which can be installed and then grow, focusing on the power and backup requirements then increasing the components which benefit the customer. For example, if you use more power at night, then a bigger battery bank might be a better option. If you work from home or run a business from home, more panels might be a better option. You also need to understand what it is you are trying to achieve, if you are just looking for a backup system for load shedding, then the design might not be the same as for a person looking for a backup and money saving solution.

Just remember, no time of use tariff or panels on the roof, your electricity bill will increase, because you need to charge the batteries using the grid power and there are losses.

There is only one consideration which must be taken into account, the budget, if you cant afford a R125 000.00 system, then you need to buy candles and adjust your lifestyle accordingly, maybe get rid of he R25000 cellphone and R1000 a month contract and focus on what is more important in life. IF backup power is not important then, candles and a smart phone it is.

An 8 kva unit has become the common unit offered to customers, why because it can handle higher loads, as panel size and power increases, so you will have to match the inverter to the panels.

I am focusing on the Sunsynk so all the specs etc will be according to Sunsynk inverters.

As I mentioned earlier, a 550 watt panels with a max current 13 amps cannot be used with a 5kva Sunsynk inverter (11 amp), so you would have to get an 8 kva inverter or get smaller panels.

The VOC (voltage open circuit) is very important and must never be exceeded, but the size of the panel will not determine the VOC, the total VOC is calculated by adding panels in series. The more panels the higher the VOC.

**Isetech** · 02-Jul-22, 07:30 AM

We move on to selecting batteries for the inverter, there a lot of calculation and explanations on the internet. What I want to focus on is the size of the inverter and the backup.

I have'nt done any data logging using a lithium battery yet ( my demo will arrive soon), so I will only be able to do true tests once it arrives.

I have done numerous tests using lead acid (gel batteries) which has got me thinking.

IF you install a 3.6 kva (3600watt) unit with a 24 VDC 100 amp/hr of battery power, you can only backup about 400 watts to last a couple hours, anything over that will drain the batteries so fast that it no longer becomes a viable backup option.

This got me thinking, why would I install a 5 kva unit with only 1 x 100 amp/hr (5kwh) battery, it just doesnt make sense. Surely it would make more sense to save money and buy a 3.6 kva and get 1 x 100 amp/hr battery. If you can only use 400 watts of the inverter power during load shedding.

Something to be aware of: Sunsynk has different models for example here are the PV string data.

3. TECHNICAL SPECIFICATIONS
 SUNSYNK-3.6K-SG01/03LP1

PV String Input Data
Max. DC Input Power 4680W
PV Input Voltage 370V (100V~500V)
MPPT Range 125~425V
Full Load DC Voltage Range 240~425V
Start-up Voltage 150V
PV Input Current 11A
No. of MPPT Trackers 2
No. of Strings Per MPPT Tracker 1+1

 SUNSYNK-3.6K-SG02LP1

PV String Input Data
Max. DC Input Power (W) 7000W
Voc Max. (V) 500V
MPPT Range (V) 125~425V
Full Load DC Voltage Range (V) 240~425V
Start-up Voltage (V) 150V
PV Input Current (A) 11A+11A
No. of MPPT Trackers 2
No. of Strings Per MPPT Tracker 1+1

**Derlyn** · 03-Jul-22, 07:47 PM

Silly question.
I have 400W panel power (40V 10A)
This is used to charge 2 of 100Ah batteries for the invertor.
The invertor is not connected to mains ie. Only the panels charge the batteries. Output of invertor is connected to db via a changeover switch like a genny installation.

Panels charge batteries via controller.

My silly question is what happens with the panel power when the batteries are fully charged ?

**GCE** · 04-Jul-22, 05:28 AM

Originally Posted by Derlyn

Silly question.
I have 400W panel power (40V 10A)
This is used to charge 2 of 100Ah batteries for the invertor.
The invertor is not connected to mains ie. Only the panels charge the batteries. Output of invertor is connected to db via a changeover switch like a genny installation.

Panels charge batteries via controller.

My silly question is what happens with the panel power when the batteries are fully charged ?

Your MPPT will throttle back to the batteries and possibly switch off if you have no load on the batteries
It is better to have load and discharge or utilize the solar

When the MPPT throttles the voltage will lift on the panels to the Voc levels which is why it is important to size equipment to Voc

**Derlyn** · 04-Jul-22, 07:17 AM

Thank you brother.
Ok, so it's a good thing to keep a bit of a load going. I've got a lot to learn with this solar and inverter scene.

Have a good day

**Isetech** · 11-Jul-22, 07:59 AM

IF you look around you will see WiFi dongles for around R 2000.

You also see it refered to as "logger" (apparently the same thing as a WiFi dongle) for around R900.

Apparently the WiFI dongle is free with the inverter and the software for the Wifi dongle is free ?

Can anyone confirm this information?

If people are charging R2000 for a WiFi Dongle, that means if you dont want a dongle you shouldnt be paying more than R18-20 000.00 for a Sunsynk 5 KVA inverter inc vat ?

**Justloadit** · 11-Jul-22, 08:41 AM

You require a wifi point which connects to the logger.
The R2000 one is actually the supply of a Pi controller.
What to me that is important with respect to these data loggers, is the following :-

How comprehensive is the available information from my inverter?
How long does the server maintain my information for, hours, days, weeks, months or years?
What does it cost to maintain the connection on the server?
Can I access the data from any web page?

What I am afraid is the the cost only for the hardware and an open access to the web page.
Who maintains the server and pays for the up keep?
It may be financed through the sale of the data loggers, but at some point the sales will drop, and it may be that the maintenance of the server then becomes unsustainable, as has happened before.

**Isetech** · 11-Jul-22, 01:35 PM

There are a couple of remote viewing options:

We use the Pi3B+ with solar assistant for remote viewing and updating setting on the Axpert type inverter. I have a few of these units on various sites. The challenge is trying to source Pi3B+ units. You can buy the complete Pi unit with the software from Solar assistant already setup or separate.

https://solar-assistant.io/

The WiFi dongle I mentioned in the thread above is specific to Sunsynk, it is supplied "free" or should suppose to be supplied free with inverter.

The one I have refer to in the previous thread is specific to Sunsynk. It should be included in the sale of the inverter.

https://arb.co.za/product/sunsynk-wifi-dongle/

You need to make sure that all the components are included in the quote, including the WiFi dongle/logger, software, Firmware updates, battery comms cable and anything else required to get your new invert operational.