Off Grid Cabin System

[flannelaxis]

I'm looking at build an off grid cabin solar system that would mostly be used on weekends. Its often used as a hunting cabin and is located in a cold region so having a heated battery is important, so the system can charge over the week when the cabin isn't heated and have power for the weekend.
I have a 240V well pump, so power for that is important, but everything else is fairly low power. I currently use a generator, but want something more long term, but having the generator as a backup would be nice.
I was thinking of getting the EG4 6000XP with one of their wall-mount batteries, but that is a lot of battery. Is there a something better? Maybe a smaller battery that works well with the 6000XP that is heated?

 

[teal95]

Rack mount battery(batteries)? Easily expandable...

 

[jvierstra]

Get twice the amount of panels you think and will want a large-ish battery bank if you dont want the sound of a generator. I have 4KW panels and a 280Ah x 48V battery (LiFePO4; Eve prismatic cells). I run a 0.5hp well pump, the inverter (Victron ~ 35W idle), and Starlink internet (~40-50W). In the winter the panels don't make much power -- for about 2 months centered on the winter solstice I was making less than 1Kw total per day (cabin is at high latitudes). The battery, however, when fully charged, lasts like 4-5 days. If you only use on weekends that should be sufficient cause the battery can trickle charge all week. You can top up with generator if you burn through all the battery storage -- this is what I do with a 5kw genset.

I think the heating the battery is a bit overblown for this type of situation. In the winter, when the temps are low (and house is not occupied), you are not making much power (maybe 100-200watts) which is like 2-4 amps on 48V system. This is not enough to damage your cells appreciably. It hovers around freezing at my cabin in winter and I dont bother heating. In fact, if they are insulated well the batteries will likely be >32F all winter. Ive had it running for 3 years -- did a capacity test a couple of months ago and no problems -- especially for a system with limited use in winter.

 

[MichaelK]

Buy a clamp meter that has the capability of reading inrush current. I have a Uni-T 216C that I recommend. Measure the startup current of your well-pump to design the system properly. Here's a pump chart I've used before. Assuming you have a smaller 3/4 hp pump, you need to feed it ~8.4A running, and 31A starting. But, my numbers are just a guess. You need to come up with your real numbers.



I'd rather see you buy a quality inverter instead of the EG4. Take a look at Outback and Schneider for quality inverters known to power well-pumps. I'm using a XW+6848 to run my 1hp well pump.

Go with a quality lead-acid battery like Rolls-Surrette, and you won't have to worry about the cold.

Make an itemized list of everything you need to power, and go from there. If the well-pump is the single largest load, and you design for that, everything else will be easy. A good rule of thumb is to have about 2X of panels as the size of your single largest load. So, if you have a pump that needs 2000W to run, feed it with 4000W of solar panels.

Don't buy automotive-style 12V panels. You get far better bang for your buck going with large high-voltage residential panels. Shop for those on Craigslist with local cash and carry pricing. Expect to get at least 2-3Watts per dollar. 4-5W/$ is better. 1$/W is a ripoff. Shipping is the killer for panel pricing, because of all that fragile glass. When you buy local, you skip all that.

 

[flannelaxis]

Until the cost of those higher end systems comes down, it would make just as much sense to connect to the grid. If I get just 1 server rack battery with a heater everything should be able to be powered for less than $5,000.
Also, with the usage, the minimum amount of panels actually makes the most sense, as there will typically be a week+ of no power usage.

 

[jvierstra]

If you’re concerned about cost, make your own battery. I built mine for 1750 all in. 48v x 280ah = 13440wh. The EG4 4800 wh battery is 1200 (almost 1/3 capacity)

 

[MichaelK]

Also, with the usage, the minimum amount of panels actually makes the most sense, as there will typically be a week+ of no power usage.

For multiple reasons, it's usually a bad decision to go with minimal solar production. Since the panels are now the single cheapest component of the systems, the only valid reason to skimp on the wattage is mounting space. I STRONGLY encourage you to maximize the solar input.

As I like to say, you'll find out. You can either listen now, or learn the hard way.

 

[seneysolar]

If the battery is going to get below freezing AND will be unattended, you should consider lead acid.

A heated LFP battery will have self-consumption trying to stay warm and it will be utilized during the time of year when PV power is minimal. Likely to run itself down while you're gone and you will arrive to a dead battery. Even a dusting of snow can make your panels useless unless someone is there to brush them off. (On this topic, id recommend an adjustable pole mount or something that can go vertical in the winter.)

Does the 6000XP keep the MPPT on when inverter is off? If it doesn't, you should consider a system with a separate inverter and MPPT. This way you can turn the inverter off while you're gone to save the idle consumption and the MPPT can stay on all the time keeping batteries topped off daily.

I use a similar principal at my cabin, I only have 2 panels (~700w) on a 415AH lead acid bank. Batteries are fully charged every time I arrive, year round, and life is good. Just my 2 cents.

 

[RyGuy]

We don't know enough about your location, weather and loads at the cabins to be super specific.

Load can vary a LOT. A refrigerator/freezer is the Item that comes to my mind that really hampers the ability to use less battery if you want it on 24 HR a day while you are there. 6000xp draws 50-74 watts at night just to be on, plus 75-200w intermittent on the refer. Plus any other phantom loads. If there are no mandatory 24hr loads you can save power by turning off the EPS(inverter AC power) at bed time if you are willing to use battery light for bathroom trips.

If all AC can be turned off when you are not there then you may get away with less pv, as long as you have enough battery(battery to load ratio) for the time you are there. I would recommend starting with at least 1 eg4 indoor battery, or 2 rack batteries.

The great thing is that you can add more battery and PV in the future. Shipping costs are a thing to watch out for. My thought is to order 6000xp, indoor battery and 10 panels if buying through signature solar. They have a 10 panel minimum. That will be about enough to max out 1 PV input on the 6000xp and get free shipping on it all. Yes it is spendy. Or buy the Inverter and 2 rack batteries plus needed parts and then source panels used or new locally.

 

[GBob]

I'm looking at build an off grid cabin solar system that would mostly be used on weekends. Its often used as a hunting cabin and is located in a cold region so having a heated battery is important, so the system can charge over the week when the cabin isn't heated and have power for the weekend.
I have a 240V well pump, so power for that is important, but everything else is fairly low power. I currently use a generator, but want something more long term, but having the generator as a backup would be nice.
I was thinking of getting the EG4 6000XP with one of their wall-mount batteries, but that is a lot of battery. Is there a something better? Maybe a smaller battery that works well with the 6000XP that is heated?

We have a similar weekend retreat in New York's Adirondacks. We find that 400 amp hours of LifePO4 batteries charged with 600 watts of panels provides all the power we need in the summer season. That includes running a tv for movies most nights. We use a 2000 watt inverter to provide the ac power for the cabin. We utilize a propane refrigerator and generator for back up, and for additional charging needed during those cloudy periods of spring and fall. We do not use the cabin in the winter. The HQST controller we use cuts of charging power to the batteries when the temperatures drop below freezing to protect them. You can run the generator to power your well, pumping into a bladder pressure tank or holding tank. We use the holding tank method, filling a 225 gallon holding tank, then use a dc powered rv on demand pump to provide water as needed for the cabin. Total investment in the solar system is right at $2000.

 

[Bluedog225]

Another vote for looking at lead acid/agm for unattended freezing. Or at least analyze it.

 

[Dinky1977]

I vote go with the wall mounted battery and plenty of panels to back it up. Also I know its a solar forum but I am going to suggest doing what I am going to do which is looking at wind and/or hydro to back up when I don't have solar. Also another reason why I plan to battery the heck out of my system and have enough to run the cabin for a while. Seen enough ideas on YouTube that work on how to charge the batteries up when you don't have the sun for the panels. But that's my half cents worth.

 

[Glock24]

Shop for those on Craigslist with local cash and carry pricing. Expect to get at least 2-3Watts per dollar. 4-5W/$ is better. 1$/W is a ripoff. Shipping is the killer for panel pricing, because of all that fragile glass. When you buy local, you skip all that.

Is that for used panels? I would've thought prices were lower over there.

Where In live everything tech related is way overpriced compared to the US, but solar panels are very cheap right now. I've got quotes for 670W panels @$185 and 550W @$120.

On the other hand (decent) inverters are like 2x the price compare to the US.

 

[MichaelK]

Is that for used panels? I would've thought prices were lower over there.

I've seen things all over the place. Some Craigslist sellers are marketing new panels, some used, and some very used. I myself have paid for used 4W/$ panels that were higher quality/output than new panels I bought retail.

You really have to show up with a voltmeter, and test each and every panel you buy. I would not recommend buying anything that was putting out more than 2-3V less than documented on the spec sheet.

 

[dopeassjackson]

If the battery is going to get below freezing AND will be unattended, you should consider lead acid

Also a weekend/seasonal cabin owner with FLA batteries..in central NY.
Mine are 4yrs old and I always leave the charge controller on. The inverter is off when I leave the cabin. I always arrive to full batteries. My system runs lights and a fridge with plenty to spare. 6 gc2 golf cart batteries.

If cost is an issue build a small system and run a generator for the 240v well pump.