I've been monitoring some weirdness on my system. I have 2x 5kw Sunsynk inverters connected to 2x 5kwh Sunsynk batteries via a copper busbar. Battery communication is via canbus on the primary unit of each and I believe the battery charging voltage is changed via this. The 2 inverters are connected via the parallel ports and the 2 batteries are connected via their RS485 ports. Each inverter has 1 PV string connected. The problem is that at certain times of day/conditions, the secondary inverter becomes parasitic and mainly gets its power from the battery (positive readings on graphs) instead of its PV string where the primary inverter sends power to the battery (negative readings on graph) which the secondary slurps up. The PV on the secondary throttles back too. I've tried to collect all the conditions and graphed it in the attached.

13:20 - secondary inverter is parasitic with charging voltage set to 54.4V
14:40 - charging voltage is changed to 56.1V and parasite is no more and both units provide PV to charge batteries (14:48)
15:00 - battery is charged and charging voltage drops to 54.4V and parasite is back
16:04 - loadshedding hits and somehow both are sucking from battery now? (16:28)
17:00 - charging voltage changes to 56.1V and both units are providing PV to charge battery (17:12)
17:42 - battery charged and both units providing PV to carry load and battery movement is minimal
18:02 - loadshedding ends and the parasite is back? (18:10)

Does anybody have any idea what's going on?
 

The abstract nature of operations of the Deye & Sunsynk inverters. These machines are not predictable when they are paralleled. The Voltronics machines are very predictable & share current equally very well. The SunDeye carries out their Parallel communication via CANbus only. The Voltronics adds Current sharing cables. 

When I first paralleled my first Sunsynk I was very open minded to see how it would cope etc. however, I still prefer the Voltronics in parallel. They are just more predictable in operation. The SunDeye is heavily dependent on the Firmware version etc & to me is a more "computer clever" Machine. The Voltronics is very dumb but just so manually driven & relies more on the operator to set her up properly. 

I guess that could be said for both but I just find the SunDeye way too abstract in nature. I guess if there is no faults generated then leave the machine to keep going. 

Edited December 2, 20232 yr by Steve87

I totally agree with Steve on this one i remembered this specific install a few years ago before i was part of this forum and boy did i have fun and games for the 2 x  8kw Sunsynk and 2 /FW 30/24 batteries to share charging equally. At the end a firmware update on both units did the trick sort off wasn't perfect but workable. Like Steve says if it works leave it be. Below the installation that got me head scratching. Or rather pulling my hair out🤣

 

 

 

 

Edited December 3, 20232 yr by TaliaB
Added sentence