Questions on solar system build

Another newbie with his head spinning looking for some assistance from the professionals. Long story short I am looking to add a complete off grid solar system to cool/heat a large room (600sqft) with a mini split when the power goes out for an extended amount of time, and will purely be used as a backup system for that reason only. With the VERY limited knowledge I claim to have, does the specs and equipment I currently plan on purchasing below work for what I am trying to do? Need more? Overkill on the equipment? Everything compatible? My wife has had it with my research hitting wall after wall so I'm trying to bring some peace back in my life .

Location: SE Georgia with pretty good clearing (Not perfect) for sunlight
Mini Split: EG4 Hybrid Solar Mini Split Heat Pump 12000 BTU / 115VAC 90VDC-380VDC / 190-1100W
System: EG4 Off-Grid Inverter | 3000EHV-48 | 3000W Output | 5000W PV Input | 500 VOC/VDC Input | Max Charging 80A
Battery: EG4 LifePower 4 Lithium Battery | 48V 100AH | 5.12kWh Solar Battery
Solar Panels (Already purchased): Currently have 6 Rich Solar MEGA 250W Monocrystalline panels (RS-M250). VMP 18.9V / VOC 22.8V / Max Series Fuse Rating 20A
Is there anything else I might be missing?


I appreciate any assistance, and please talk to me like a child because I know nothing of watts, volts, amps, etc.

EG4 3k + Lifepower4 is a good backup for a small mini split yes.

There's not really a need to use a solar hybrid mini split. You could use any 9k and probably most 12k mini splits on the AC out of the 3k.

You are at risk of that battery running out overnight, and the solar providing inadequate power. But that depends on how insulated the room is. I would take a wild guess that you are likely to be short on both.

hwy17 said:

EG4 3k + Lifepower4 is a good backup for a small mini split yes.

There's not really a need to use a solar hybrid mini split. You could use any 9k and probably most 12k mini splits on the AC out of the 3k.

You are at risk of that battery running out overnight, and the solar providing inadequate power. But that depends on how insulated the room is. I would take a wild guess that you are likely to be short on both.

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Makes sense. With the battery I kind of assumed I would need more but will have to take my chances until I can afford a 2nd one. So just for conversation sake, if I ended up going with a 9k mini split (115V / 810-840W) would I then currently have enough solar power because of the lower wattage or would I still need to add more panels? If I need to add more panels, do I need to stick with the same ones or can I add another one with higher wattage?

How long is "an extended amount of time" and can you define the scenario in which you would want to use this system?

Q-Dog said:

How long is "an extended amount of time" and can you define the scenario in which you would want to use this system?

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I plan on using this system for cooling/heating emergency use, such as if the power goes out for a day or 2 or if there is a grid outage. Georgia can get pretty hot so I'm just trying to cool/heat a small section of my home so we can at least be comfortable. My hope is that I can run solar during the day, and with the one battery to have use for at least half of the night. I realize I would most likely need a second battery for 24hr use.

If the panels are moving say 1200w all day running the mini split, who is charging the batteries?

With enough solar connected to it, the hybrid solar mini split can run as long as the sun shines. You might have enough panels to run the mini split, but you do not have enough panels to run the mini split and the inverter. and the 2 systems can not share the panels.

If you only need to run the mini split during the day, the battery and inverter are not needed. If you want to run through the night you will need more batteries and you will need a way to recharge those batteries, so more panels or a generator.

sunsurfer said:

If the panels are moving say 1200w all day running the mini split, who is charging the batteries?

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Unfortunately I am unaware on how that works as well

Q-Dog said:

With enough solar connected to it, the hybrid solar mini split can run as long as the sun shines. You might have enough panels to run the mini split, but you do not have enough panels to run the mini split and the inverter. and the 2 systems can not share the panels.

If you only need to run the mini split during the day, the battery and inverter are not needed. If you want to run through the night you will need more batteries and you will need a way to recharge those batteries, so more panels or a generator.

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Ok. So if I go with the EG4 solar mini split, I need enough panels to provide enough juice to the unit itself needed during the day, and have a separate inverter, battery, and a separate solar array to charge the battery during the day and to use at night?

So if I go with a normal 9k mini split, I have the panels & inverter attached, and have a 2nd array to charge the battery during the day and then attach the charged battery to the system to use at night?

Sorry for all the newbie questions, I just want to make sure I have a full understanding because while YouTube is helpful, there still is not a lot of clear answers I can find there.

If you install a regular mini split with an inverter, batteries, solar panels, you need enough battery to run the amount of time you want to run, enough inverter to handle the load of the mini split, and enough panels to recharge everything.

Let's say the mini split is running on high and needs 1100 watts. That would be 1.1 kWh of power just for the mini split. And you need that for every hour the mini split runs. Your single battery is 5120 watt hours, or about 5 kWh.

You have 1500 watts of panels. If they could supply full output all day (they can't) it would take about 4 hours to recharge your battery. BUT, you probably want to run the mini split during the day while you are charging the battery. You need more PV to be able to run the mini split and charge the battery at the same time.

It is just math.

Justlivin said:

Unfortunately I am unaware on how that works as well

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If power is down during the day, you will be running the A/C off the panels. Any remaining solar will go to charge the batteries. If you run the A/C on low for say 16 hrs over night and it is on low power, say 500w, you would need the panels to charge the batteries at 1000w for 8 hrs to cover the over night. Thats 8,000 watt hours stored ( the battery you listed would only hold a bit of 5,000 watt hours)

So if you have say 1500w coming in(not likely on a hot day), and the A/C is using 1200w(likely a bit more), that is only 300w x 8 hrs or 2,400 watt hours. You can run the A/C for 5 hrs after sunset.

This is just a rough example. Your system is a bit small, it will do work but likely not enough for your region.

Q-Dog, we posted the same thing at the same time, we must be in sync this morning.

Q-Dog said:

If you install a regular mini split with an inverter, batteries, solar panels, you need enough battery to run the amount of time you want to run, enough inverter to handle the load of the mini split, and enough panels to recharge everything.

Let's say the mini split is running on high and needs 1100 watts. That would be 1.1 kWh of power just for the mini split. And you need that for every hour the mini split runs. Your single battery is 5120 watt hours, or about 5 kWh.

You have 1500 watts of panels. If they could supply full output all day (they can't) it would take about 4 hours to recharge your battery. BUT, you probably want to run the mini split during the day while you are charging the battery. You need more PV to be able to run the mini split and charge the battery at the same time.

It is just math.

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Ok so it sounds like I'm pretty underpowered and think it's pretty clear I need another battery & more panels to make this work. Do I have to go with the same exact panels that I already purchased or can I go with used ones at a higher wattage? I thought I remember hearing either the wattage or the VMP has to match? Thank you for your time BTW

sunsurfer said:

Q-Dog, we posted the same thing at the same time, we must be in sync this morning.

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Same question as Q and lets see if it matches I appreciate your assistance as well.

The panels should be similar if you want to run them in the same string as the existing panels. If you run them in separate strings it may not matter ... depends on if they use the same charge controller.

Typically we start with what loads need to run and how long they need to run, before buying stuff.

Q-Dog said:

The panels should be similar if you want to run them in the same string as the existing panels. If you run them in separate strings it may not matter ... depends on if they use the same charge controller.

Typically we start with what loads need to run and how long they need to run, before buying stuff.

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(Typically we start with what loads need to run and how long they need to run, before buying stuff) Assuming I probably should have bought the panels last.

Ideally my preference would be to run them off of the same string to avoid having a 2nd box. So with that said, I will need say 2500W of 250W solar panels, and the 2nd battery added to keep things comfortable for a good amount of time without expecting perfection? I apologize, electrical is not my strong suit.