Hi

I want to ask about the connections when connecting 2x inverters and 2x batteries together please.

On the AC Side: I believe there should only be a single set of breakers for both inverters?

On the DC Battery Side: A single dc dis-connector connected to both batteries and inverters. Or should each inverter have its own dc dis-connector?
BMS Cable: Is this correct as per wiring diagram?
PV: Feeding to one inverter at this stage. (If ever required, I will add pv to the other inverter.) BUT WILL THE PV PANELS CHARGE BOTH BATTERIES?

DC Battery Cables: Will 50mm do or do I need higher?

AC Cables: 10mm or 16mm? Distance is about 2m from DB and inverter.

Idea is to pay for as little as possible electricity. So no charging from AC is allowed. Will probably have 3x or maybe 4x batteries with initial install.

Consumption is about 15-20KWH a day.

 

A) The two 63A DP MCB in the Main DB must be a SP MCB for protection of the cable and I would eliminate the 63A coming from the Changeover DB.

B)In the Changeover DB I would change the 63A DP MCB to three 63A DP Isolators and add two 40A SP MCB for protection. The one Isolator is used to isolate the complete DB and from there a Isolator and MCB for each of the inverters - The reason why an Isolator is used and not a DP MCB is because a DP MCB may not be used to disrupt the current flow of a neutral, only an Isolator may disrupt the current flow of the Neutral conductor.

C) For the Outputs of the two inverters it is also better to use separate 63A Isolators and 40A MCB's.

D) Then I would use 2 change overs instead of one:
Change Over 1 Input One from the Output of the inverters and the second Input for a generator then you take that Output of Change Over 1 to the one Input of Change Over 2 and the second Input of Change Over 2 to the utility then the Output of change over 2 back to the Main DB via a 63A isolator and a 63A MCB.

E) I do not see any surge arresters in the change over DB, I would highly recommend that a surge arrester is installed on the input side and on the output side of the inverters.

F) I would use 16mm2 cable to be on the safe side.

G) I would install a DC MCCB (Molded Case Circuit Breaker) for each of the inverters on the battery side. I purchased a couple of DC MCCB's from e-Glow that I use with my setup (https://e-glow.co.za).

H) I would use 2 X 35mm2 crimped together in 1 X 70mm2 lug for both positive and negative from the batteries to the MCCB's and then on to the inverters.

I) I would use this calculator to calculate the solar yield https://offgriddiy.co.za/solar-energy-available-at-a-given-location/

J) I do not have experience with the Hubble batteries so I cannot advise on the battery communications.

 

PS: Always install a DB which is a bit bigger if there is a future need to expand.