Understanding a Sunsynk inverter

[Isetech]

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

[Isetech]

Tip

We had a battery go into shutdown and we couldn't get it to start charging.

The reason it went into shutdown, when it reaches 80% DOD or 20 % SOC, it doesn't switch off and stop discharging, in fact it drops rather quickly, unless you pull the fuse or switch off the battery, it will just keep dropping.

Hopefully the battery doesn't drop to zero % DOD. The IP 65 manual indicates that you shouldn't recharge the battery in less than 12 hours, however the technical support will tell you to increase the charge amps. Maybe I need to re check the manual.

You will notice a red fault light, you have to switch off the inverter and battery, try restart the battery and inverter, lower the cutout setting and low battery setting and wait for the inverter to normalize. IF it doesn't normalize and the red fault light keeps switching on, you pretty screwed.