Understanding a Sunsynk inverter

[Isetech]

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]

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]

Tip:

It is very important to start the battery first, then switch on the inverter.

Make sure the "on" light in the top left corner of the display indicates ON.

Do not switch on the AC until you have setup the unit and the normal light is on (green).

[Isetech]

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]

Tip:

Battery settings are important, and you need to make sure the battery is communicating.

A very expensive lesson I learnt, your grid settings are very important. The battery will not charge if the grid settings are not correct. You can change the frequency from 60 to 50 hz (as per SA) but the inverter will not automatically reset the upper and lower limits. You have to manually reset the upper and lower limits.

Make sure you understand how to initialize the battery, the 5.3 kwh battery for example you must first switch on the rocker switch, then press the button and hold for 3 seconds. The new IP 65 battery 5.1 kwh battery there is no rocker switch and no delay to switch on.

[Empowered]

Hi Isetech, hello and thanks for this informative thread.

This caught my attention and I'm wondering if you could explain more please...

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.

Someone mentioned this to me recently too. Why can't one use 550watt panels with a 5kva inverter?

[Isetech]

With the limited knowledge I have of solar design, I stick to the data sheets.

I have read of others using 550 watt panels.

When I do the install at my workshop, I might try it to see what happens.

Do you have any input to share ?

Living and leanring by the day, always open to suggestions or a bit of technical advice.

Hi Isetech, hello and thanks for this informative thread.I havent

This caught my attention and I'm wondering if you could explain more please...



Someone mentioned this to me recently too. Why can't one use 550watt panels with a 5kva inverter?

[GCE]

Hi Isetech, hello and thanks for this informative thread.

This caught my attention and I'm wondering if you could explain more please...



Someone mentioned this to me recently too. Why can't one use 550watt panels with a 5kva inverter?

Ratings on electrical equipment are there for a reason - The design of the electronics , heat dissipation etc. on the MPPT
Would be like taking an 11Amp contactor and running 13 Amps through it every day for an hour or two - It is going to fail prematurely which means your expected 5 year warranty will fall away as all that information is logged
The voltage on the MPPT is even more critical as edge of cloud effect can lift that voltage by 20% depending on time of day.

You would not buy a 1/2 ton bakkie to take a 750Kg load at red line on the motor between PE and Cape town as a courier service and expect the bakkie to give you the same life expectancy - Brakes will fail prematurely , motor will go through head gaskets , overheat on hills etc - You would expect problems , same thing with an MPPT that is been driven hard.

[Justloadit]

Ratings on electrical equipment are there for a reason - The design of the electronics , heat dissipation etc. on the MPPT
Would be like taking an 11Amp contactor and running 13 Amps through it every day for an hour or two - It is going to fail prematurely which means your expected 5 year warranty will fall away as all that information is logged
The voltage on the MPPT is even more critical as edge of cloud effect can lift that voltage by 20% depending on time of day.

Since a PV panel is a current source, the only change in the voltage of the panel is due to the effect of temperature.
The open circuit voltage between say -5°C and 25° to 55°C can say as much as 5V up when cold to down when hot from the specification sheet which is done at 25°C
What changes is the amount of current the panel provides. It can vary fr0m 0.5A early in the morning say at 08H00 to FSD amps example 11A between 11H00 to 13H00during a sunny day. Provided the Azimut angle is correct and panels facing North in the southern hemmisphere, and that there are no shadows and the panel is clean and free from bird droppings. As clouds come over, the MPPT voltage remains the same, only the current changes.

[GCE]

Since a PV panel is a current source, the only change in the voltage of the panel is due to the effect of temperature.
The open circuit voltage between say -5°C and 25° to 55°C can say as much as 5V up when cold to down when hot from the specification sheet which is done at 25°C
What changes is the amount of current the panel provides. It can vary fr0m 0.5A early in the morning say at 08H00 to FSD amps example 11A between 11H00 to 13H00during a sunny day. Provided the Azimut angle is correct and panels facing North in the southern hemmisphere, and that there are no shadows and the panel is clean and free from bird droppings. As clouds come over, the MPPT voltage remains the same, only the current changes.

I tend to disagree in part - The panels will get to a point where they can no longer increase current or the inverter clips the current to stay within range and the voltages rises .
I have always understood that the MPPT can take a surge in current for short periods but a surge in voltage causes the damage .

We have a system extremely close to the coast and it is affected with the sea mist causing edge of cloud type effect. The system generally runs around 600Vdc per MPPT and have seen it vary from 500 to 700v during the day .
Have also noticed that if the incoming voltage goes out of spec that the inverter is sync to and it cuts the current that the voltages rises , also around 100vdc