System capacity, and batter choice

[dbuckles]

I posted this in Beginner's Corner first, and then saw this forum and thought of an additional quesiton. New to this.

I'm having trouble with what seems to me to be the first question to answer: what system capacity do I need that is "just right" for my requirement: to run a 14 cubic foot electric fridge (115 V 60 Hz, 2 A) for two summer months (July-August). And add periodic load to this to run a fireplace insert blower 1.2 A only as needed during one month in early fall (September). I use propane for cooking, and have very minimal lighting needs easily satisfied with propane.

I need to consider as well that the cabin is on a small island (1.5 acres) in northern Ontario (Canada), and inaccessible in the winter months. Temperature there today is - 17 C (without the wind chill).

Questions:
1. What system capacity do I need? Is the "classic" 400 watt much more than I need? What is just right?
2. What key component choice do I need to make to conserve the possibility of a small future increase in capacity with additional batteries/panels? A few lights, for example. No plans for T.V., power tools, etc. None!
3. What about the batteries considering the location and winter storage temperatures? Cost is not my main concern. I understand Lithium may be too sensitive to consider, but I don't like the idea of storing over winter acid batteries on an island with pristine water all around. I can't remove the batteries in the fall (too many other things to do, and I'm getting old).

Thoughts?





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[FilterGuy]

1. What system capacity do I need? Is the "classic" 400 watt much more than I need? What is just right?

You need to do an energy audit to answer this. Try this resource:

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

2. What key component choice do I need to make to conserve the possibility of a small future increase in capacity with additional batteries/panels? A few lights, for example. No plans for T.V., power tools, etc. None!

First thing is the inverter..... make sure the capacity of the inverter can handle your future needs
Next is the Solar charge controller. If you don't buy a large enough one, you will have to add a 2nd one when you add panels.

What about the batteries considering the location and winter storage temperatures? Cost is not my main concern. I understand Lithium may be too sensitive to consider, but I don't like the idea of storing over winter acid batteries on an island with pristine water all around. I can't remove the batteries in the fall (too many other things to do, and I'm getting old).

The main thing for storage is temperature. In storage they can easily handle 10deg F 0deg F starts to get to a point where you may need to consider how to keep them warm. What temps does it get down to on the island?

 

[dbuckles]

Thank you for you thoughts filter guy. I haven't done an annual review of weather at the island, but temperatures can drop to -20 F at night and even colder for a number of consecutive days in January and February. Nights of -10 F are common from Dec to March. The winter is long, overall, with fluctuations as well. Thanks for the energy audit calculator.

 

[FilterGuy]

Thank you for you thoughts filter guy. I haven't done an annual review of weather at the island, but temperatures can drop to -20 F at night and even colder for a number of consecutive days in January and February. Nights of -10 F are common from Dec to March. The winter is long, overall, with fluctuations as well. Thanks for the energy audit calculator.

Your situation is similar to my hunting cabin where I store the cells over the winter. The lowest recorded temp for the area is -30F.

I built a box with R30 insulation all around (using foam board insulation). I then added this for heat:

Simple, Indipendent Battery Box Heater

To get the document, click on the orange button at the top of the page. This is a simple 20W battery Box heater that operates independently of the rest of your system. I use this for storing unused cells in a very cold climate, but it can be...

diysolarforum.com

I calculated that the box only needs ~8-9Whr/day to hold temp if the outside is 30deg F colder than the inside of the box.

On top of that the insulated box is inside a well insulated cabin, so I am confident the temp is not a problem.

Note: Over the winter, the batteries are completely disconnected from all loads. They do not even have the BMS hooked up.

I have heard that Winston Cells are more tolerant of colder weather, but have not been able to confirm that. Furthermore Winston cells are a *lot* more expensive.

 

[dbuckles]

Good info. Sorry, are you using acid or lithium batteries? I'm a beginner, so another dumb question. I thought these systems were set up to use solar energy in the winter to keep the batteries on a trickle charge all winter.

 

[FilterGuy]

I am using LiFePO4 cells. The set-up uses a hydro turbin for power and that is shut down over the winter.

 

[dbuckles]

Understood, thanks. I will continue to explore the pros and cons of battery options (acid/lithium, and trickle charge) for storage in cold weather settings.

 

[dbuckles]

I have a plan for a remote cabin system, with specific energy requirements. Comments?

Cabin, remote location central Ontario

SOLAR IRADIANCE (Facing south-south west (22.5 degrees) kWh/m2/day panel set at 59 degree angle: June 5.41; July 5.31 Aug 4.81 Sept 3.95

Energy audit:

• 10 cubic foot fridge, 600 Wh/24 hrs, operation July 1 to end of September only
• Fireplace insert fan 1.2 A) (mainly in September)

Design:

Solar Panels: 3 x QCELL-335-60BLK

Controler: OutBack FLEXmax 80

Inverter/Charger: Kisae KI-SW2012-55 Sine Wave

Battery Pack: 6 x PH-225 solar battery

Small generator for top up