New Member with an Off-Grid Cabin (solar newbie)

[a Cuppa Coffee]

Hi. I am new to this and am having a problem with a DIY off-grid system that I bought from Eco-Worthy.

I am a very smart guy ----meaning that I seldom have difficulty figuring out how to succeed at something----, and installed my system with the help of my father (a retired electrical worker) with fairly decent ease. I purchased a bundle with 960watts of panels (received 6 panels at 160 watts each), an MPPT controller, wires and connectors. My new cabin is built to be very efficient electronically. I wired the panels in to a battery bank that's 12v, 1800amp hours.

The system worked fine for 3 days. On the 4th day, the MPPT controller switched to "Absorb". As of this morning, my batteries are only at 10.3 volts, my panels are inputting 18v (under load) to the controller, but the batteries aren't charging and my 2500w Sunforce Inverter errors with "I.N.L", low voltage. I have messaged the manufacturer, but they've yet to reply.

Any thoughts? All politely placed advice is welcome.

[SunEagle]

Hello Cuppa Coffee and welcome to Solar Panel Talk

I see 2 issues. The first is that with 960 watts of panels for a 12v battery system you need an 80amp (960w / 12v = 80amp) MPPT CC so that 20amp is way too small.

Next issue (which is a presumption on my part) since I do not know exactly what you have, but I image your 12volt 1800Ah battery system consists of a high number of batteries wired together in parallel. Any time you wire more than 2 batteries in parallel you run a high risk of not charging or discharging them equally which can quickly kill one or more of those batteries.

What is that battery system comprised of and how are they wired?

Also once you get a larger MPPT CC the amount of amps it can provide for charging needs to be about 1/10th the Ah rating. So if you do get 80 amps out of it your battery system should not be much bigger than 800Ah (max ~ 960Ah) and composed of lower voltage batteries (2v, 4v, 6v) with 800Ah ratings wired in series.

[a Cuppa Coffee]

Hi. Thanks for replying. I was concerned that the company I bought it from sent me a 20amp MPPT, but figured they would not bundle something with the 6 panels that wouldn't work. As for the battery bank, my 12v 1800amp bank consists of 16 6v 225ah VMax AGM Charge tanks wired in series parallel.

[Logan005]

You are already in trouble, 10.3 volts indicates you have already damaged the battery bank. you need a generator ASAP, to charge that battery bank and sort out the damaged units.
This is far too large for a 12 volt system. you need to scrap the 12 volt inverter and get a 24 or 48 volt inverter and rewire your battery bank. If you truly want an off grid cabin 12 volts is not the way to go. rewire your batteries into two strings of 8 giving you 48 volts and same AH no mater how you calculate it. This is assuming you have any batteries left after you get proper charge on them.

[SunEagle]

Hi. Thanks for replying. I was concerned that the company I bought it from sent me a 20amp MPPT, but figured they would not bundle something with the 6 panels that wouldn't work. As for the battery bank, my 12v 1800amp bank consists of 16 6v 225ah VMax AGM Charge tanks wired in series parallel.

Because you only had 20 amp of charging you never put back what you took out and chances are you have drained that battery bank over the last few days. Hopefully you haven't damaged them all.

To get your battery matched to your panel wattage you need to reduce the number to maybe 8 total. That would get you a 900Ah 12volt system which is about what your panels can properly charge but based on your daily watt hour usage it might not be enough.

If you used a max of 25% of the battery system that comes to about 2700 watt hours a day. (900Ah x 12v x 25% = 2700wh)

You also still need to get that 80A MPPT charge controller. Make sure you get one that is a true MPPT and not a cheap knock off. Depending on the panel Vmp rating a good MPPT might allow you to wire those 6 panels in series.

Now if you determine you need more than 2700wh a day then you will need to build a bigger battery system as well as get more panel wattage. If you go more than 1000 watts you will have to go with at least a 24volt battery system which will require a different inverter.

[a Cuppa Coffee]

The quickest thing I am taking from this is that the company that I bought the system from (Eco-Worthy/DC House) should not have paired a 20amp MPPT Controller with a 1000W panel system. Am I just in saying that? Should I demand they replace it with a larger controller?

[SunEagle]

The quickest thing I am taking from this is that the company that I bought the system from (Eco-Worthy/DC House) should not have paired a 20amp MPPT Controller with a 1000W panel system. Am I just in saying that? Should I demand they replace it with a larger controller?

Well unless those panels have an Imp around 3 amps/ea and they expect you to wire them in parallel to get 18amp total then I would say they did not give you the correct CC and your system will not utilize the full wattage of your panels.

Most quality MPPT CC are rated based on your total panel wattage divided by your charging voltage. 1000w / 12v = 83.3 amp which would mean you need an 80A MPPT. Going with more wattage puts the amp rating above 80A and really drives you toward a higher charging voltage for your battery.

[a Cuppa Coffee]

I should be able to get by on 2700wh per day. It is a new home, is just at 500 sq feet, and all the appliances have been bought to use very little electricity per day. All the lights on in my entire house at once uses less than 50watts (LEDs). My fridge and freezer are very small, and designed to be used in an RV or Solar situation. Even our PC in the house is a microPC with a solid state system, no fans. I had read of people building a bank like mine, I now know that (apparently) they were blowing smoke. Your thoughts though is that a 900AH battery bank would still work as a 12v system with the panels that I have...assuming that I get a proper 80amp MPPT CC?

[Sunking]

I am a very smart guy, and installed my system with the help of my father (a retired electrical worker) with fairly decent ease.

Not so much, neither of you knew what you were doing. You are in deep chit and lost a lot of money.

First huge mistake is using 12 volts parallel batteries. With 12 volts at 1800 AH requires a minimum 2000 watts of solar panels and 2-80 Amp Controllers. You are no where close. Your batteries are already in bad shape from extreme abuse.

Largest 12 volt system you can make is 1000 watts and a 80 amp controller with a 12 volt 800 AH battery. Even that is extremely foolish as it should be 24 or 48 volts. Best idea for you is to get all your money back and start over and get at least a clue what you need.

You did everything wrong with incompatible parts. None of the panels should be in parallel, nor any battery in parallel. You are using expensive Low Voltage Battery Panels when you should be using inexpensive high voltage Grid Tied panels of 250 or more watts or higher wired in series and 2 volt batteries.

[a Cuppa Coffee]

Sunking - That is the point of me posting here...to attempt to get proper advice (without abuse) to fix the erred situation I am in with what I've purchased. I can rewire my batteries if needed. I have disconnected them from the load for the entire day and they seem to be trending back towards 12v on their own. That said, I will put a battery charger on them and check to see if any are damaged.

[a Cuppa Coffee]

This is what I purchased. I still have a little bit of money to fix my erred ways. This is why I joined, to get advice to fix this. If I got duped by a bad seller who sold me incompatible parts, so be it.

If my batteries aren't damaged, and I can get the right controller (80amp), and I have these panels already. What's your best advice, polite advice, to get my situation corrected.

I currently possess the panels shown, 16 6V VMax AGM batteries, and a 12v 2500Watt inverter.

I can, I believe, still return my inverter and get a different one. If not, I'll list that one on eBay or somewhere and buy another one.

Positive advice and critique is most welcome.

I am powering a 500 square foot Tiny House/Cabin. If I turn on all the lights in the house, it's less than 50watts. I need to run a microcomputer (solid state, no fans), a 13" monitor, my satellite modem, a small 110AC/12vDC fridge and a very small freezer...during night time hours. I would like to watch a bit of TV (36" UHD LED TV) and perhaps play some Xbox One each evening.

My heat is wood. I have a passive cool air intake system installed in the house. An on demand propane water heater.

I have designed the house to run on solar. We have a really crumby electric company here, and while I could grid-tie, I don't want to deal with them of I don't have to.

[Sunking]

Get rid of the 12 volt Inverter, configure the batteries for 48 volts, get a real 40 amp MPPT controller for 48 volt battery, 48 volt inverter no larger than panel wattage, and a total of 2000 watts of panels wired in series as high of a voltage as your controller will allow around 120 to 130 volts.

1000 watts is not enough to support your batteries, 2000 watts minimum, configured as 48 volts with a 40 amp controller. At 12 volts battery with a 20 amp MPPT max wattage is 250 watts period.

Everything you bought was incompatible. with your controller, the batteries are only getting 1/10th of the power they need. That is why they are dead. Anything gyou take off grid is going to cost you 5 to 10 times more than buying it from the power company. You are going to be replacing those batteries every few years if you give them TLC. You already damaged them and will need replaced very soon.

[SunEagle]

This is what I purchased. I still have a little bit of money to fix my erred ways. This is why I joined, to get advice to fix this. If I got duped by a bad seller who sold me incompatible parts, so be it.

If my batteries aren't damaged, and I can get the right controller (80amp), and I have these panels already. What's your best advice, polite advice, to get my situation corrected.

I currently possess the panels shown, 16 6V VMax AGM batteries, and a 12v 2500Watt inverter.

I can, I believe, still return my inverter and get a different one. If not, I'll list that one on eBay or somewhere and buy another one.

Positive advice and critique is most welcome.

I am powering a 500 square foot Tiny House/Cabin. If I turn on all the lights in the house, it's less than 50watts. I need to run a microcomputer (solid state, no fans), a 13" monitor, my satellite modem, a small 110AC/12vDC fridge and a very small freezer...during night time hours. I would like to watch a bit of TV (36" UHD LED TV) and perhaps play some Xbox One each evening.

My heat is wood. I have a passive cool air intake system installed in the house. An on demand propane water heater.

I have designed the house to run on solar. We have a really crumby electric company here, and while I could grid-tie, I don't want to deal with them of I don't have to.

If you look at that data it states you have a 40amp MPPT and can use 960 watts to charge a 24volt battery not a 12volt.

So the system is technically acceptable since the MPPT can handle the input of those 6 x 160watt panels if you wire them as shown in the diagram. But you have to wire your batteries as a 24volt system so your inverter is the wrong kind if it is rated for 12volts.

And since you can only get 40 charging amps your battery system needs to be sized as a 24v 450Ah system. So that is 2 parallel strings of 4 of those 6v 225Ah batteries wired in series. You only need 8 batteries for that set up.

[a Cuppa Coffee]

Yes, but my controller I received is only 20amps. They didn't send me the one in the listing. In the hectic environment of building my house, I did not realize I didn't get the right controller.

[a Cuppa Coffee]

SunEagle - I had to search Amazon, but this is the one they sent me. I guess "buyer beware", but lesson learned buying from Eco-Worthy/DC House.

[SunEagle]

SunEagle - I had to search Amazon, but this is the one they sent me. I guess "buyer beware", but lesson learned buying from Eco-Worthy/DC House.

Unless the 40amp CC was listed as part of the package it might come down to buyer beware. Maybe they will take it back and swap it for the correct one. Let us know.

[a Cuppa Coffee]

Thanks. I'll let you know how it turns out.

[Sunking]

Makes no difference if it is 20 or 40 amps is too small either way at 12 or 24 volt battery for the capacity you have. Minimum 2000 watts at 48 volts with 40 amp controller. Or 80 amps at 24 volts.

[a Cuppa Coffee]

Yes, yes...your input has grown tiresome. It is clear that your are the very busy negative voice in this forum. I have only been using Solar Panel Talk for under a day and your negative input has me regretting it.

[SunEagle]

Makes no difference if it is 20 or 40 amps is too small either way at 12 or 24 volt battery for the capacity you have. Minimum 2000 watts at 48 volts with 40 amp controller. Or 80 amps at 24 volts.

I agree that the OP's battery is way too big for his panel wattage and CC. He might be able to salvage his system if he can get the correct CC and reduce his battery system in half to about 900Ah. The problem I feel is that most of his batteries may already be nothing but boat anchors after being majorly discharged.

The big issue is what will his true daily watt hour use be and does he have enough panel wattage to charge the matching battery. If not and he ends up needing an 1800Ah battery then going to a 24v or 48v battery would be his best option.