Off Grid System - 1st timer - Advice / checking for correct setup

[PySoMaNiC]

I was curious if you guys can help to make sure I have everything I need for my off-grid setup, and hopefully tell me anything I am missing.



List of components

Victron MPPT 100/30

Victron 24V/1200W Inverter

Q-cell 430W Pannels x2

120AH Deep Cycle Lead Acid Batteries x6

15A DC Breakers x 2

40A DC Breaker

DC Breaker Box for 4 Breakers

100A MEGA Fuse x5

MEGA 100A In line Fuse Holder.

100FT 4AWG Wire

30FT MC4 Connectors x2



----BATTERY BANK WIRING-----

I would like to connect my batteries in groups of 2 in series, and have 3 of those in parallel making a 24V, 360AH Battery Bank using 4AWG Wire. (Picture attached of how I believe I should wire this setup).

-----PV WIRING---

I believe I should wire the solar panels in series, having 1 15A Breaker between both solar panels, and another 15A Breaker between the Solar Array and MPPT.

-----BATTERY BANK to INVERTER----

I am going to use 4AWG wire between the battery bank and inverter, I plan to place the 100A MEGA Fuse in line with the positive as close to the battery as possible.

----BATTERY BANK to MPPT----

I was going to use 4AWG wire between the battery bank and MPPT, and I plan to place the 40A Breaker in line with the positive as close to the battery as possible.

-----SOLAR MOUNTING----

I am also planning to run these solar panels outside on the ground, do you recommend or have any mounting equipment for this?

-----GROUNDING THE SYSTEM----

How can I properly ground this system, where do I connect ground and what size wire / grounding rod should I use?





I plan to just run my AC Appliances fron the plugs provided in the inverter, 3.5 CU FT Freezer, some led lights, television, and charge laptops / cell phones / cordless tools etc...


Series-Parallel.PNG

[chrisski]

1B389EA6-109E-410D-A202-9B188187B2E0.jpeg I’d really check your power requirements. Six lead acid batteries will net yo360 ah overnight or 180 ah planning for bad weather of one night. THat’s not a lot of power. The inverter could draw .5 - 1 amp just to turn on, and that cuts into it. You could not run my laptop for more than 1.5 to 4 hours with that power.

I don’t know if your freezer will run off your inverter. Unfortunately an compressor freezer needs several times its rated wattage to start. Seems you need to buy the inverter and hope it works.

[PySoMaNiC]

Hey,

First off thank you for looking at my post. My main purpose for this setup is to power my freezer which is going to be converted into a fridge, even as a freezer it consumes 197KwH a year, I plan to charge my devices including rechargeable LED lights during daylight hours when my solar panels are producing more then I am consuming. Anyways my worry is not the amount of capacity I have as I would just add more batteries to my setup should that be a problem.

I am more concerned about the system setup, making sure I have the right wire gauge for my setup and fuses / breakers in the right place. I am still also unsure if I should wire my solar panels in Series or Parallel. I understand the benefits of both in terms of shading and the change in Volts / Amps but I have yet to find any information as to how this effects charging of my batteries. What I have gathered is with an MPPT it does not matter if I increase the AMPS or Volts as the controller is smart enough to charge equally on both?

[chrisski]

I’d determine wire based off ampacity. I expect 150 amps max from the inverter. I’d use 1 AWG with the inverter and battery.

150 amps is an uneducated guess. The actual math is:

inverter watts x low voltage cutoff / inverter efficiency / x 1.15 for surge = expected amps with safety factor

Whatever the formula says is also the fuse size.

not everyone used the 10 volt inverter cutoff, but amps skyrocket as volts drop to keep the same. You’ll find other formulas that will justify smaller wire. 4 AWG wire will work, but needs to have the correct insulation rating. Because of voltage loss and it getting hot, I would not use it.

D87FC7B0-DA76-4696-B8B2-64DA96286A99.jpeg

[PySoMaNiC]

I was told that the 24V Victron Inverter has a built in 100A Fuse thats not replaceable and so was told to place my 100A fuse in line between the batteries and inverter as close to the battery as possible, but I guess 4 AWG wire is not rated for 100Amps so you are correct and I am glad I see this now, would have had a nice fire hazard sitting around.

[chrisski]

I was told that the 24V Victron Inverter has a built in 100A Fuse thats not replaceable and so was told to place my 100A fuse in line between the batteries and inverter as close to the battery as possible, but I guess 4 AWG wire is not rated for 100Amps so you are correct and I am glad I see this now, would have had a nice fire hazard sitting around.

24 volts. I missed that. 4 AWG, with the correct insulation will suffice. By my chart that is 75°C. I like getting 60° C insulation, so 2 AWG. 3 AWG will work but is hard to find.

[PySoMaNiC]

I still dont see how you got that off your chart I dont see anything about 24V in there, but I did use some calculators online and it does say you are correct with a 2% voltage drop I can run 4AWG almost 20 feet. Do you have any idea about my solar panel setup how I should set them up either parallel or series? And can I place the breaker inside closer to the MPPT?

[sidpost]

Why lead-acid batteries instead of LiFeP04? A little more expensive and you need a BMS (<$100) but, a lot more lifespan and allows a deeper discharge without harm.

[PySoMaNiC]

I actually bought a 200AH LifePO4 from renogy but after reading and now dealing with their terrible customer service I have since cancelled my order. I just cant justify the cost increase for the same amount of capacity at the moment, and lack of reputable dealers in Canada that are decently priced, the ones that are reputable charge 300-400% more then LA. I know that in the long run it is worth it, but this is just my 1st setup and Costco has a great warranty and price point 170$ per 120AH Deep Cycle LA. I figure in 3-5 years there will be a dramatically cheaper LifePO4's and I will probably end up building my own from cells.

On top of all that to have the same redundancy is also a cost increase, with 6 LA's I have some room for failure.

I was under the impression the MPPT is smart enough to manage the charging of my battery bank? Can I not get DOD from voltage of the bank?

[sidpost]

I bought CATL 302Ah cells for $143/ea (USD) so, you would need 8 for a 24VDC system. With "Depth Of Discharge" differences, In my case, 122ah lead-acid batteries are ~$105/ea (USD) and would require multiple strings for the same discharge capacity with a much shorter overall lifespan.

Like you, I would stay away from Renogy batteries if I needed more than what one single battery would offer.

I would suggest you get batteries from Jenny at https://www.docanpower.com/ where I got mine. Being in Canada may or may not present an issue if you need warranty service but, these are really good batteries and are not rejects or recycled Chinese bus batteries. Amy is another well-regarded supplier.

I, and many others, are very satisfied with both options which are China-based. Stick with EVE or CATL new cells and you will do well. Your SUPPLIER out of China matters as much or more than the 'brand'. With Jenny having batteries in Houston, Texas, that option was an easy one for me. Previously, I was looking at a LTL (Less Than Truckload) shipment out of California from China which has been widely reported as a good experience in recent times when buying through Amy.

Finally, if Renogy batteries were attractive to you, I would suggest looking at Signature Solar (.com) GYL/EG4 lithium batteries out of Sulphur Springs, Texas. I have been to their facility and they 'assemble' them there based on Chinese components at the present time (EG4 packs).

[PySoMaNiC]

I appreciate the advice and info, but I am not really sold on this yet I still trust that I can walk into any Costco here in Canada and get a replacement in the next 3 years if I have any issues. Where as any of these companies you talk about I have to deal with over probably the span of many weeks while I sit at home in the dark. Those websites seem very shady especially the one you actually linked, I have seen these before and so far have only seen very negative reviews on their owners being left in the dark as the suppliers they bought from closed up shop.

[sdold]

I'd wire the panels in parallel since the combined Voc in series could exceed the 100V input limit of the controller. How cold does it get there? Also there's no reason to have a circuit breaker on the panels unless you want to switch the panel off for servicing. It's not needed for overcurrent protection with only two panels in parallel. Make sure it's a DC-rated for the voltage and current.

[PySoMaNiC]

Hey I was thinking the same thing about wiring them in parallel, and got a phone call from a supplier today to help me out pointing out that in the cold weather I would have a problem with probably burning out the MPPT over time as its so close to the max voltage. It does get down to -30C here in the winter. I also remember reading that as long as my short circuit current was less then the current of my MPPT that no fuse / breaker was needed, so I am a bit upset that they up sold me 2 breakers, though they have been the most responsive and helpful suppliers yet. I still dont understand the point of wiring panels this size in series since they are all 45volts + so they are capable of charging a 24V system, having them in parallel makes more amps and faster charging no? or does it actually not matter at all with an MPPT?

[sdold]

The MPPT controller uses whatever power is available from the panels whether they are in series or parallel, and converts it to the appropriate charging voltage and current for the battery. In parallel the panel current is doubled, in series the panel voltage is doubled, but either way the total panel power is the same so the charge controller output current and voltage to the battery is the same.

Remember that power is volts x amps, so with series or parallel, the total power harvested by an MPPT controller is the same. The advantage to wiring panels in series is that, with higher voltage and less amps, you can use smaller wire to carry the same power. On the other hand parallel wiring can better tolerate partial shading. But either way is OK as long as the series wiring doesn't exceed the max voltage of the controller, and parallel wiring still has high enough voltage to allow the MPPT controller to operate.

Also a simple switch at the panel connection to the charge controller would be enough to turn off the panels for servicing if you want that ability, as long as it's DC rated for that voltage and current. The reason breakers or fuses aren’t needed for the panels is that they have limited current capability and can’t produce enough to damage the wires, unless three or more are in parallel, which then would require a fuse/breaker on each parallel panel.

[sidpost]

...Those websites seem very shady especially the one you actually linked, I have seen these before and so far have only seen very negative reviews on their owners being left in the dark as the suppliers they bought from closed up shop.

If you are talking about the Docan Power out of Houston, TX, calling them 'very shady' is WRONG. I have been there personally and while not a Mega-Lo-Mart, they are a real tangible entity in Texas.