New to solar, building off gird cabin.

[Dansjeep2000]

Wow there is sooooooo much to learn and I don't know where to start.

I am building a small 400 sq ft cabin in northern michigan and have no access to the grid. I would like to set up a simple solar power setup to power the basics.

I need to power lighting (led), a small television, a radio, maybe a few other simple comfort items in the future.

I am leaning towards a 12v system so I can run as much as possible at straight 12v (lights for example) and only use the inverter for that items that require ac power.

I already have batteries (got a killer deal) and a xantrex 1700 watt inverter.

[Dansjeep2000]

I have 10 of these batteries. All test good to go.

Any advice on what brand and size panels? Also what charge controller.

[Mike90250]

Those are sealed, AGM batteries, 2 years old already. What is their warranty in years, expect them to fail 6 months past warranty, they have very good internal timers!

Wiring more than 2 batteries in parallel is tricky, wiring AGM batteries in parallel, is even worse because of their low internal resistance.
read this article http://www.smartgauge.co.uk/batt_con.html about parallel batteries.

Depending on how many you install, then we can chose the charging gear.

[Dansjeep2000]

I got the batteries for $35 each. I couldn't pass them up. I was thinking about just 2-4 battery system for the cabin.

[Dansjeep2000]

Very interesting link, I had not thought about the Unequal discharge rate.

[Sunking]

Let me guess you bought those batteries from someone connected to a telephone or communications company right?

[Dansjeep2000]

Let me guess you bought those batteries from someone connected to a telephone or communications company right?

Yup

[Sunking]

Yup

Well they were pretty smart guys because it would have costed them more than you paid to dispose of them.

[Dansjeep2000]

Well since they test fine I'm not sweating it.

[thastinger]

Since you have the batteries already the best way to maximize their use and life would be to do 4 of them in series which would give you a 48V 110Ah battery bank which would give you enough for a system capacity of about 1.5Kwh per day using generally accepted design guidelines. You could also wire them up as 2 4 battery stings in parallel which would give you enough battery bank for about 2.5Kwh day but you'll likely have issues keeping them balanced since they are AGM and you are new to the care and feeding of a battery bank.

You should first review all of the stickies at the top of the off grid forum section then you should buy a "kill-a-watt" meter and figure out your actual loads as what you listed as desires likely exceed the 12V realm and with you already buying the batteries, you've pretty much eliminated the capability of anything 12V anyway. I'd count on powering everything via the inverter. Just get a good PSW inverter so any motors or coordless battery chargers remain happy.

Just an FYI, the system in my sig cost me about 5K and it is designed to deliver 2.5Kwh per day. You'll learn to manage the power and watch the weather so that you can get more from it on a sunny day after the batteries are charged back up but you have to design the system with some reserve capacity for snow/cloudy days etc and for the least amount of sun hours.

Budget in a generator, you'll have to have one in order to EQ the battery bank when needed once you kill the AGMs and move to FLA batteries.

[Dansjeep2000]

I should also add that this is a vacation cabin and will only be used weekends and 1 week in the summer.

[thastinger]

I should also add that this is a vacation cabin and will only be used weekends and 1 week in the summer.

I'd plan to sell that inverter and plan a 48V system (will know more when you post your actual loads). The loads design the system so the loss of the batteries or/and inverter purchase may end up being your first lessons in off grid system design.

[SunEagle]

I should also add that this is a vacation cabin and will only be used weekends and 1 week in the summer.

If you are only going to use the cabin for that short a duration then I would suggest you find a generator and battery charger and forget about the solar panels. The panels and racking will be a big cost and really not be used for most of the year so using a generator/charger would be a better investment to keep those batteries happy.

If you were staying at the cabin for much longer duration then adding solar panels could help except in the Winter where you probably will not have enough sunlight to recharge the batteries.

[donald]

Are you planning to have propane for cooking?

You will need to have a generator. But I suggest a smaller inverter type than you can easily take home at times, especially for the winter. A couple solar panels that can be put vertical in the winter would be useful and interesting. I think some battery and solar is useful and interesting, but not 900 AH storage. Will you have internet access?

You may want an AGM system long term. But probably with considerably smaller AH, and with as few of cells as possible. In your situation I would probably design a 12v system with a couple adjustable panels. Then use a small Yamaha generator, and have propane for cooking and some heat. I would use a 12v fridge, because I don't like managing an ice chest. I would size the solar to run the fridge may-aug only.

[Dansjeep2000]

Yes I will be using propane and wood for heating and cooking. I have a small 900 watt generator now (older john deere I've had for years) runs like a champ.