Off-grid On-grid UPS backup system, both my 9 year experience and advice for a new one

[ABarbarian]

I have a solar power system been running since 2013, my goals were primarily to stabilize power for a bunch of computers and a few lights when power cut. No interest in selling back to the grid and not so worried about ROI, I understood I would probably not get my investment back, but the savings do offset the price of the system a great deal.

 

Because my main concern is consistent power I run off the batteries constantly.

 

Attached is a pic of the system I have been running, the components were:
- Solar Inverter STECA EXTENDER XTM 4000-48 48V/3500Watt
- Solar Charger Controller STECA TAROM 440 48V/40A w.LCD
- 8x 12V/130Ah batteries
- 12x 130W solar panels

 

The basic idea is the batteries are always being charged from the solar, and used until they get low then an alarm sounds and we connect the grid to the inverter. I understand the inverter is configured so that when there is grid power it uses that, when no power coming in from grid it pulls from the batteries. It should not push power from the batteries to the grid.

 

I added the switch between the batteries and the inverter when the first set of batteries started to die as I was not sure if the inverter also charged the batteries from grid when grid was connected, I did not want that to happen but was still using the failing batteries as long as possible, the extra switch allowed me to protect against that.

 

The system has worked pretty well and have only changed the batteries once, unfortunately I don't get any reporting nor able to check the programming of the inverter, but it all seems to run well enough. Switching the grid on and off works well without any interruption to running computers.

 

I thought I would chuck this up as an example, see if anyone sees any glaring faults, but also to help explain the new system I am preparing for a second location, wanted to ask peoples opinions about components and configuration.

 

Similar goals for the new location, although a consideration I have is I want to build for about half the final expected capacity now, adding the other half in about a years time. Final capacity will be about double my old system (enough for about 800-1000 units).

 

The information I read suggests not matching batteries/panels of different ages etc, best to buy them all in the same batch, that makes adding more capacity at a later date not optimal.

 

I have noticed a lot of systems are using multiple inverters in parallel instead of a single inverter, I guess this works out cheaper, that gave me the idea of breaking the system into two sets of solar systems, each powering different loads around the house. Each set will have it's own inverter, panels and batteries, that way I can buy one set now, and the other later, without combining different sets of batteries or panels.

 

My idea is to have 3 sources of power, solarA, solarB, and grid. I would have them all feeding AC to a batch of switchboards at one location, those switchboards would have cables feeding to all the different loads around the house, I would cable it in a way that I could move loads around between the switchboards depending on which I want powered from which source.

 

I am hoping to have good reports from each solar system to be able to make choices about moving loads around over time to use power as efficiently as possible.

 

I would also like to allow the grid to feed into each inverter similar to my old system with a switch, so if either solar system drains low an alarm goes off and we can temporarily switch that inverter to grid until the batteries charge back.

 

I would expect each of the solar systems to handle about 400-500 units of power.

 

So that is my idea, anybodies thoughts, either about possible issues or suggestions what components I should buy.