Tiny home needs some solar please advise

[offgridsolarguy]

I have a 250sq ft cabin in Northern Ontario, Canada and I would like to add solar. I would like to power a 10 cu ft apartment size fridge, 12v water pump, a few led lights, and charge a few phones or laptops. We are at the cabin for 3-5 days at a time. Here is what equipment I have now:
9x 330w 24 volt solar panels
4x 100ah 12 volt lithium ion batteries
1 x 3000 watt inverter.

Can someone please advise what sizes of wires and fuses I need to connect this all together? Can I add a few more batteries? Should the batteries be in series or parallel? How should I connect the solar panels? Series or parallel or a combination? Any similar systems with drawings would help me alot! Thanks everyone!

 

[MisterSandals]

4x 100ah 12 volt lithium ion batteries

Are these LiFePO4 or other chemistry?
Are your batteries connected in parallel (12V system?) and in a balanced manner?

The volts will determine the amps.

How will your array be configured? 9 panels is convenient for all in series or 3S3P.
Again the voltage, amps and wire length will determine wire size.

So need more info to answer your questions.

 

[Rednecktek]

What voltage does your inverter call for? You can't use a 24v inverter on a 12v battery so it's kinda gonna be a deciding factor. Hopefully you're not trying to run a 3000w inverter on 12v, that's a LOT of copper and HONKIN fuses.

Have you picked out a SCC yet? You'll need to match that to the voltages of your panels (PVInput) and the battery voltage (watts / volts = amps required) to make best use of the panels you have.

So, grab us a little more info like:

Voltage requirements of the inverter (12v, 24v, 48v)
Solar panel VoC, Vmp and Isc (on the back label)
Total list of any 12v devices including the water pump and their rated amperages (should be on a sticker on the device)
Wish list of things you'd like to be able to add in some day

You're starting an adventure, we're here to help.

 

[glandpuck]

I have a 250sq ft cabin in Northern Ontario, Canada and I would like to add solar. I would like to power a 10 cu ft apartment size fridge, 12v water pump, a few led lights, and charge a few phones or laptops. We are at the cabin for 3-5 days at a time. Here is what equipment I have now:
9x 330w 24 volt solar panels
4x 100ah 12 volt lithium ion batteries
1 x 3000 watt inverter.

Can someone please advise what sizes of wires and fuses I need to connect this all together? Can I add a few more batteries? Should the batteries be in series or parallel? How should I connect the solar panels? Series or parallel or a combination? Any similar systems with drawings would help me alot! Thanks everyone!

My advice would be to forget the solar panels since you are way up North and subject to extreme cold and snow. You could come to the cabin and find the system out of service due to snow you can't clear off the panels and ice too and then the batteries too cold to charge.

Your best bet would be a small diesel generator and battery charger or a Polar brand DC generator to charge your battery bank and then you can just worry about expanding your battery bank. There are now batteries with built in heaters as well as UL approved cabinets with heaters inside them to warm batteries so safe to charge.

Oh and one final thought: No cup for Leafs this year either!

 

[MichaelK]

Looks like you bought a bunch of random stuff on impulse, and now you are stuck with putting together an very imbalanced system. I'd say the single most important mistake is going with a 3000W 12V inverter. Second biggest mistake is buying Li batteries for a location that gets extremely cold.

Why is 12V a mistake? With 2970W of panels, trying to charge a battery at ~12.5V, even with 85% de-rating, you are going to make (2970W/12.5V) X 0.85 = 202A of current. That is really an absurd amount of current to attempt to deal with. Even with 24V, that's still >100amps.

Does the manufacturer of your batteries state they can be wired in series for 48V? That would cut your amps down into the 50A range, which is far more reasonable for your other equipment. But, you still need to be concerned about the winter. Your Li batteries will suffer permanent damage if they receive a charge below freezing, and I can't think of a better place for that to happen than northern Ontario. If you want to keep those batteries the system must be completely shut down in winter so there is no possibility of the batteries getting a charge.

You made no mention at all about what electronics you have. That will be the deciding factor on how to wire your panels. Are these panels 72-cell? What is the Vmp/Voc for them? That will decide which charge controller to use. You could wire three in series for a 3S3P configuration with a 200V charge controller. Take a look at Epever's Tracer 6420 controller. I wire my 72-cell panels in 3S for my Midnight 200 controllers.

Here is what I would do. Sell the 12V inverter, and replace it with a 48V model. Get a DC-DC 48V to 12V converter to run your pump. Buy eight 6V golf-cart lead-acid batteries and wire them in series in an either/or configuration with the 48V Li battery. Completely shut off the Li battery in the fall and run on the golf-carts only throughout the winter. Only switch back to the Li battery at the spring thaw.

Your lack of proper research before laying down money means you will be spending a lot more in the long run to make it all work properly.

 

[Rocketman]

Assuming your 120v electric needs really are well within the inverter you already have and you don’t want to resell and change to 24 or 48v.

The 12v batteries need to connected in parallel- I would hook them onto a bus bar with exactly the same cables (length, size, etc).

After the busbar connect a shunt based battery monitor (like Victron Smartshunt or BMV712) and a class T fuse.

Then to a distribution bus bar - you will need 4/0 cables to the inverter and between the bus bars.

Fuses on every item leaving the distribution bus bar.

You will probably want more than one SCC - Solar charge controller or maybe just one large one. You will be overpaneled. So don’t worry about being able to use all the watts when it’s nice weather - in not great weather you will be using it all just at 10 to 25%. We need to know exactly the specs of the panels to recommend a SCC.

Make sure the batteries are completely disconnected for your winter - you will destroy them if charging them below 32 deg F. (Although if you plan to use it in winter there are ways to keep them warm if they are watched over).

Good Luck

 

[Steve_S]

Below is one of my Simple Generic Logical Diagrams of a "Component" based system using batteries in parallel. This indicates where fuses/breakers should be located for an A-Typical system.
This shows it a separate Solar Charge Controller, a dedicated charger & an Inverter or Inverter/Charger unit.
Most installations have an Inverter/Charger which eliminates the dedicated charger.
* Batteries in Series increase the voltage.
* Batteries in Parallel increase the capacity (Amp Hours).

NOTE, the diagram uses a Dual Busbar setup with the upper busbar showing how the separate devices can be interconected and fused. There are solutions to put all of that together professionally by using DC Sub-Panels / E-Panels with proper DC Breakers with a Main Master large scale breaker. E-Panels can be expensive - depends on what you want and how "pro & safe" you want your system.

12V @ 250A draw from battery can support a MAXIMUM of 3000W + surge, and that is the top edge limit... If for any reason you require any higher wattage you will need to step up to 24V/48V. However, from your description, you will likely not be pulling anywhere near 3000W continuously.

Solar Panels need a Solar Controller which you failed to mention. Given the odd number of panels, their wattage & voltage, I think a single Midnite Classic 200, possibly a Classic 150 could manage that likely in a 3 Parallel strings of 2 panels. NOTE a Midnite Classic 150 or 200 in Canada will cost about $1100, alternately a Victron 150 or 200 Volt SCC may do as well... Solar Panel specs will be required and then the software on the sites can work out panel array config.

Battery Fuses: Each battery should be fused @ 100A "IF" they are 12V/100AH LiFePo4. For 12V MRBF are acceptable (cost effective)

MRBF Terminal Fuse Block - 30 to 300A - Blue Sea Systems

Easily and economically satisfies ABYC 7 circuit protection rule by mounting on a 3/8 battery post, battery switch or bus bar.

www.bluesea.com

A REAL BusBar capable of dealing with the amperage: There are cheapo's that will cause issues.

Pike Industries | Pike Industries Busbars

pikeind.com

Battery Switch: is important to disconnect everything when working on equipment & or for storage.

e-Series On Off Battery Switch - Blue Sea Systems

350 Amps continuous rating for inboard gasoline or diesel engines.

www.bluesea.com

Solar Controller Fuse/Breaker: There are usually TWO Breakers, 1 for the incoming solar power & 1 for outgoing power to batteries. The sizing is determined by the Solar Controller & Panel configurations. Fuses can be used but is not the "usual".
Independent Charger Fuse/Breaker would be sized to it's Max Output Amps.
Inverter/Charger Fuse/Breaker would require a Class-T or Mega Fuse @ 250A, a 200A Would work as well and still allow for surge handling.

Wiring: Because you went large Inverter that is capable of 250A Draw, you need to use 4/0 Gauge to handle it... NOT Cheap stuff. You will need equal length 4/0 wires from Inverter to Battery Bank busbars and then equal length wires from there to battery terminals. We Recommend using High Grade Welding Cable with ultra fine wire (very high strand count) with Tin Plated closed ends.
Wire: https://www.solacity.com/product/2-awg-4-0-awg-welding-wire/
Terminals: https://selterm.com/collections/tin...ery-cable-ends-wire-lugs-marine-grade-md4038p

NOTE: Fuses, Breakers, Wires etc can ALL be purchased from Solacity (Kemptville Ontario)

Solacity - Canadian Green Power Goods & Great Advice!

YOUR Canadian source for all renewable energy supplies! Buy solar panels, charge controllers, inverters, batteries and more at great prices. We design too!

www.solacity.com

FOR YOU TO DO:
1) Full & Proper description of ALL your hardware, (Make/Model/Version) Solar Controller, Inverter or Inverter/Charger, and BATTERY INFO
2) Specifications of the Solar Panels (Make/Model) and the specs on the back sheet.
3) Is cabin heated or not (LiFePo4 LFP cannot be charged below 0C Temp ! Some have heating pads but not all. Some do not even have Cold Temp Protection (which can be hazardous)

 

[50ShadesOfDirt]

In a cold environment such as yours, I'd add the following:

1. a portable generator (propane, auto-start, etc) and fuel system (bottles, or site fuel or equivalent if available in your area)

2. heated space (propane, heater w/ thermostat) for area holding solar gear

3. monitoring/automation (over the internet, by someone else, etc.) w/ temp sensors, cams & such

With the first item, you have power no matter what scenario/emergency pops up. I think this should be completed before anything, as this prepares you for emergencies. You also have backup recharge capability if solar output is low or no-go at the time(s) you are up there.

With the second, your equipment is better able to handle the extremes of your area, and LiFePO4 batteries (high cycles, no maintenance) are a possibility.

With the third, you are able to keep an eye on things, and/or it shuts down automatically if any scenario pops up requiring a shutdown. In this case, you still have generation for power.

Many of Steve_S's posts have the details of canadian particulars (equipment availability, purchasing, etc.), so a search of his posts would get you further along ...

Hope this helps ...