What do I need

[derbuechsenmacher]

I'm planning out and acquiring the components to do an ac coupled battery system. I'm using the eg4 18k inverter, and leaning towards the ruixu battery. Other than the wire, what else do I need? DC breakers? Disconnects I will eventually add additional panels into the inverter (probably next year,. I already have a bunch of panels which I acquired used (I have at least 10 left after setting up my camper solar at my camp))

 

[robbob2112]

The EG4 manual has many sample diagrams in it - pick the one that most closely matches what it is you are going for.

Do an energy audit to determine what your actual need is - this determins the number of panels and size batteries to connect.

From your description it sounds like you will be doing a critical loads panel with circuits moved to it.

So do things in this order or it will cost you money in the end.

• energy audit
• goal
• plan
• buy

 

[derbuechsenmacher]

Already did all of these. I'm looking for any ancillary parts that I might need like DC breakers (which I think will only be needed when I go and add additional pv panels).

 

[robbob2112]

well, unless you share what your plan is it is hard to suggest what you need.

Inspected or not?
panels on roof or ground mount?
Do you have metal conduit for any PV DC wire that will be in or on a dwelling? PVC is ok in the ground and only to the first point of penetration.
3 strings or more? If 3 strings or more you need a combiner - UL listed if being inspected.
Do you have MC4 connectors that match the ones on your panels? Since they are used it might behove you to pre-check the connectors and if they don't match what you have cut them off and redo them. Also check the diode if present to make sure not blown.
Do you have everything it takes for racking?
How many batteries?
Using a rack or some other mount method?
Do you have fuses, disconnects, breakers in your kit already or do you need to add them still?
Are you making your own cables or do you need to order them?
If making them do you have a real set of crimpers verse the cheap $40 AMZCNC pair that is metric verse awg dispite markings? Temco is a good brand. If being inspected the crimper must imprint the AWG size into the metal.
If making do you have UL listed lugs? Temco, marine and harbor, selterm? Do you have a variety of sizes both awg and hole size?
Do you have bus bar sets - depends on design as to how many and what amperage?
Do you have the various sizes of wire needed including an EGC wire to the panels to attach the frames to house ground?
Have you prepared the mounting space - cement board on the wall to mount to so it can take the heat?
Ionizing smoke detector in the space preferably attached to house smoke detectors?
Do you have a shunt of the appropriate size?
Do you have no-ox-id special for every contact surface - prevents corrosion and makes for a better low resistance connection.


There are a hundred other qustions but these are the things I would ask myself. And I would make a detailed plan of where wires run, current in the wire, what size wire, what size OCP, etc... More detailed than the single line drawing the AHJ and electric company requrires if you are grid tie.

 

[derbuechsenmacher]

Right now it will be an ac coupled system. The existing grid tie system will go to the generator input of the eg4 inverter. The eg4 will go into the grid where the enphase system does today. All will be in metal conduit. The battery I am planning to use is https://www.ruixubattery.com/product-page/lithi2-14-3-battery-bank. The battery is all contained so no rack etc is necessary. Adding panels is a future item, so consider them out of the picture for now. I will be making my own cables and have the right crimpee necessary to go up to 00 cable. Mounting space has already been preped. Cement board on top of 3/4 plywood. I have (will source locally the appropriate guage wire so that is not an issue). This all is going in a workshop building as that is where the enphase system is connected. I'm not certain what additional breakers (I don't need any more in the panel as that is already where the enohase connection goes. The battery has its own breaker, but ithink I need another between the battery and the eg4 inverter. That's really where my questions lie, is the battery breaker sufficient, or would it be best to add breakers between the battery and the inverter. I don't think I need a pv disconnect as that already exists for the enohase (yes when I add panels I will obviously need to add pv disconnects for that). The battery has built in busbars for adding more battery, so I don't think I would need additional busbars. I am working on my drawing/plan and plan on documenting everything including the wire guages (the battery looks to need 6awg, I plan on using 4 since I like to be oversized). The battery to inverter connection will be under 3ft long. The 50 amp to the grid will be 6, even though 8 would be sufficient

Basically it will be. Pv---> enphase system --> eg4 generator input
Eg4 grid --> to existing grid connection
Battery --> Eg4 battery

 

[derbuechsenmacher]

Ok. Just checked the battery and I need to use 1/0 wire from the battery to inverter connection so I will adjust my plan accordingly

 

[robbob2112]

I would add a class T fuse 20% higher than the invert max draw just before it. Fuses react faster than breakers. It doesn't hurt to have both. This protects everything else in case the inverter shorts.

If you have more than 2 batteries in parallel it is best to connect to a separate bus bar. If you daisy chain the batteries one to the next and Z connect the endpoints the middle battery ends up being charged and discharged less. While the endpoint cables get hotter than the rest.

Make sure locally acquired wire is fine stranded welding wire rated 105c, this isfor the DC wire.. AC wire can be standard THHN. For enphase devices they output AC power.

There is a link if you follow my signature line on connecting parallel batteries.

When you have the detailed drawing we can look farther.