Jaco P Bloem

Hi Erwin I do not have knowledge of the Growatt inverters, but have two Mecer Axperts in parallel. You are correct in that all similar AC in/out puts and Battery DC are parallel connected on the two inverters, except the PV inputs. You may not bridge the PV inputs as then you effectively parallel the 2 DC input sources (that you have designed with care in your drawing 😉) and short-circuiting the two mppt chargers. I am sure it will be similar with the Growatt: on the Axperts you connect a ton of communication and current sharing cables (a parallel communication kit) .. in order for the inverters to cleverly balance the power drawn from the 2 different PV sources, battery charging and AC (load) output.. (Perhaps check with the supplier?) Kind Regards Jaco P

Hi Jannie I have a similar setup, with the same 2 Axperts in parallel but only 20 panels (12 x 330W on the one and 8 x 360W on the other). You can install your first set (array) as 7s+7s to the one inverter and the second set as 8s+8s to the second inverter. Then all 30 panels are utilised. {This is, you parallel two series strings of 7 panels in set 1} The 2 sets do not have to be identical as they each go to their own MPPT charger, as long as the parallel strings are equal and you stay below the 450V. The operating Voltage is lower than the stated Voc (Open Circuit V), so you may see a Voltage of less than 300V dc on the inverter for set 2. The current source in both sets will then be 18Amp (max operating I). Let us know please how it goes! (you will notice how clever the Parallel configuration will utilise the power drawn from the 2 uneven PV sets) Kind Regards Jaco PS: I did enquire my supplier in the past and Voltronic replied to say it is safe to over-design the PV by 20% that is 5400W (max!) on one inverter, however the Inverter will not draw more than 4500. You should be OK with 16 panels (4800W) in the second set..

Hi As the AC input and output and even the battery DC side is bridged out in the parallel config, my opinion is that the issue is in one of the PV input sets. If I recall correctly, you have posted 98V and 114V of the 2 PV inputs. If the 270W panels operate at around 30V, the 114 seem OK (depending on the time of day). The 98 V set is suspect, how does the 'open circuit' voltages test? You can perhaps measure the sets and strings and panels, the should give similar readings each time. Hopefully just a connection issue in one string.. ((Just measure and check connections safely - it can be a 'shocking' experience ☺️) Let us know please - I run a similar setup, but the power drawn from the PV sets are equal, even with the 2 uneven sets I have. Greetings Jaco P

Hi Jay You seem to be OK, I also do not have a mechanical bypass, with all the in and out going breakers one can safely disconnect the inverter - but we will have to do some wiring in case of a permanent issue.. You should consider adding surge protection on the PV (on or close to the Inverter). There is discussions in this forum on PV DC fuses - but each string should ideally have a fuse just above the max current source. So if 1 string has 2 in serie that source is app. 2 x 9amp so a 20Amp fuse is OK. (My Axpert can handle 450 V DC, so I have 8 panels in serie - the source stays 9 amp, so a 12 amp fuse in that string is ok.) On my second Inverter I have 12 panels: 6 in serie, 2 parallel strings - the source becomes 18amp so a larger fuse (20amp) is needed if combined. Why not consider more Series connections? it lowers the current. The battery should have a DC fuse even with breakers, you can check the battery specs but 125amp should do it.. Keep well! Jaco

got it! I do have a heat pump installed but will supplement it during the winter daytime with the 2kW element. I will install a normal DB timer switch to prevent it also from draining they batteries. (I have tested this and if you gets the temp high enough it will last until the PV take over again) I am sure you do get automatic time based change-over switches if you want. But while you will take energy from the grid for the Geyser in any case, you may as well drain your batteries to the point that your home load would have, then let the Inverter switch all load to the grid and wait for PV.. Keep well!

Hi, I have a similar intention but first need to take out my old 4kW element and throw it as far as possible! 🤭 I guess in your case it depends on the Inverter and batteries (if any) you will install. You may choose to let the Geyser function as is with it's thermostat as an AC load on the Inverter, and let the inverter switch over to the utility (grid) by means of settings. For instance, when sufficient battery energy is available at night the Geyser will be supplied via DC but at a selected Voltage (or SOC) the Inverter will switch back to Utility. You can also select for the Utility to charge the battery or wait for Solar to take over in the morning.

Hi, I have an Mecer Axpert MK II 5kW inverter with 2 x 48V Lithium Iron batteries. I do not use the communication cable as it was confirmed several times now that this Inverter does not communicate with an external battery. Fortunately the batteries do have their own BMS, so you set one as the Master, the other as follower and a comms cable between the batteries (only). On the Axpert the battery type is set to 'user' (setting 5), and then check the battery specs for setting the charge amps, charge Voltage and Float V. Is your setup complete and the batteries used as a DC input at least ? Greetings Jaco P (Bloem)