@Bruce Hill I'm going to post on your post to shine some light and give more info for future users.
The one you got is a 2011 model. We did a check on it via the serial number at MLT. MLT factory is in Cape Town so if you get any problem, they can repair it. They call this range inverter the 2 Gen powerstar. You can get all the info on there website with manuals and tests. https://www.mltinverters.com/resources.html . This inverters was still on the City of cape town NSR097 list till 2017. You must run it as a standby sseg now or off grid.
This is real hybrid inverter, it can import and export power, it mix grid with solar and battery and generator. You can adjust it all in it's settings. You can even run a gridtie solar inverter on the output part of the inverter so it will supply power to that inverter to keep it running.
They super rebust inverters and can take a punch. This inverter is 6kVa rated but is actually 8kw. It can 8kw for 30min anr 12kw for 30sec. It can pull 150amp DC easy. On the battery and coms part.
Lets start with the coms part. You will see on the side of the inverter is plugs and rs232 connectors. The inverter got smart controls that can ryn via contactors so you can run the geyser and Aircone and what you want to control. It's got a control that you can use to control lithium batteries when it's full to stop charge but stress on that part. There is rs232 output. You can buy a Bridge from MLT that plugs into rs232, this sends info to MLT portal where you can see all your details of your inverter. It's basically a raspberry Pi with a rs232 converter. Some of the later models came out with pi build into the inverter. You vam find scuda software on there site and you can use a computer to log onto the inverter.
FreedomWon and Bluenova design a small device that connects to the inverter and that will inform the inverter what to do.
The inverter got it's own build in shunt so it can see when you charge and discharge so it can worked out and build it's own algorithm to show how much power is left in the batteries. You can put in the AH size in the inverter.
There is more info arround all this stuff.
Arround batteries and size. Stay clear of Pylontech. They 15s configuration and can only charge max at 53v and the C rating is to low. You will need a bunch of pylons to keep iy happy. This inverters is design to work with 2v lead acid sells 500ah and up. This inverters is power hungry and wants allot of amps. It can pull 150amp plus and you must run 50mm2 dc cable plus.
This inverters can charge up to 62v plus so check if you can get lifepo4/lithium battery that 16series configuration inside. There is some brands that you can check for. I'm running a 35kwh DIY setup, one unit is 280ah with it's own bms, and 2 units that is 200ah a unit with each there own bms. They not communicating with each other but there is ways you can do it with some python scripts and pi and more. You will see in my photo that I'm running some Victron stuff to. I'm running smart shunt with a Cerbo and victron smart mppts. We will get to that part now.
You don't need coms between the battery and inverters. It's got a 4 stage charging and that you vam adjust in the invertet settings. You basically switch of the equilize. It was design to equilize acid base batteries in pre set time that you can pick. It runs a sd card in the bard and super cap to keep settings and data and time and date and got some interesting things on the board.
You basically adjust the inverter to the specs what the manufacture is giving and stay in that specs. When the inverter pics up that the battery is getting fuller, then it will start pulling back in bulk charge and go into stage 2 and 3 and then 4 that is float. The inverter can adjust 0.00v increments. Don't adjust the cell count in the inverter because it was design to run 2v cells. So when you work out charge and pre volts settings then you will do it 0.00v × 24cells. "2v × 24cells = 48v".
Im running mine 54.6v bulk charge and 54v float. Close to 4 years and still going.
I started out with my first setup with Micrcare mppts and micrcare battery monitor setup with the shunts just to check the solar production. This you run on the back side of the inverter via the mppy input. It's got a 100ah shunt so it can see the solar going in an going to the battery. This way it can see if it needs to add grid power to assist with supplying the ac output and charging. On this setup i ran 3kw array with 14.4kwh storage. That kept us going for summer daya and winter i sometime had to drop in the grid for hybrid mode to assist with supply.
The inverter runs 2 contactors inside it, so basically isolate it self from the grid when the grid drops our if it the volts of thr grid go to high or low the Hz flex is to big. It will reconnect back to grid after 45sec following to NSR and sans rules. This can be adjust if you got the password.
With my setup now I'm running 10kw array with 250/100 and 150/100 victron mppt with smart shunt between the 35kwh lifepo4 storage and inverter and Cerbo GX and Et122 per inverter so that i can see the inverters AC output on the VRM portal. I'm running my setup standby sseg with a 3 way change over. Setup was commissioned begin of the year and registed and not ones we used grid power so far. Stove is gas.