2 x Growatt SPF 5000 ES Parallel installation with 2 x 5KW LiFePO4 batteries

[asankha]

Hi All

I have purchased two SPF 5000 ES (5KW) inverters from Growatt and two 48V 100AH LiFePO4 batteries from GSO. Using a busbar, I am planning to connect each battery and inverter as follows.

I am assuming that at any time, each battery to the busbar current will not exceed 100A (since the battery is 100AH), and input drawn by each inverter from the total 200AH battery bank capacity will not exceed 100A. So, I am thinking using 2 AWG wires for ALL of the below wiring, and the use of the 150A/60VDC MCB before the inverter is good enough. Is my understanding correct?

Thanks
asankha

 

[Hedges]

You connected both batteries to one end of busbar, both inverters to opposite end.
100A + 100A = 200A flowing in busbar.

I'd connect one battery to each end, one inverter to each inner stud.
Only 100A flows through any part of busbar.

We like breakers/fuses as close to battery as possible.
Only Positive needs breaker, not negative too.

But you may also need breaker at busbar to protect cable to inverter. So keep two where shown, just move close to busbar.

 

[asankha]

Thanks Hedges.. The Growatt manual shows two breakers in all diagrams.. see the 2 inverter setup, which has a breaker in the negative too.. so I was assuming it to be correct. The 2 AWG should be okay for the wiring right?

 

[timselectric]

2 AWG is fine, as long as the cables are less than 10' long. If longer, I would go bigger.

 

[Hedges]

If vendor calls for breaker on both poles I guess that's the thing to do.
I'm accustomed to battery negative being grounded, breaker on positive only.

Sunny Island has an internal 2-pole breaker, which would isolate it completely.
They say either positive or negative grounding is allowed, but optional.
U.S. code requires grounding at the voltage a full-charged 48V battery reaches.
If negative grounded, I don't know of a reason to fuse negative, only positive.

Depending on max allowed fuse/breaker rating of inverter, you might avoid needing additional breakers on inverter wires if sized to handle sum of two battery breakers.
Since you have the possibility of current from one battery exceeding other while feeding two inverters, depending on max allowed battery current, think through breaker size and cable size. Maybe wire both batteries to middle of busbar, both inverters to outside ends.

 

[timselectric]

Over current protection is only needed on one side of the battery circuit. (Usually the positive) but, I prefer a two pole breaker. To serve as an isolation disconnect. For service and maintenance.