Alaskan Cabin Build - Solar Design

Bradish

New Member
Joined
Dec 16, 2021
Messages
5
Howdy all -

New to the forum, looking to source the vast array of knowledge. Been reading some of the material in the Newby and FAQ section, but not finding everything I'm looking for.

Figured I would start a thread to ask a few questions and document the install process once I get there.

I am building a cabin (nearly a house) in Alaska. This is in a recreational area, considered semi-remote, and definitely off-grid. If anyone is interested I am documenting that build process on the Small Cabin forums here: https://www.small-cabin.com/forum/6_10671_0.html . I won't rehash everything that has gone into that, but try to focus on the solar portion here.

Design theory:
I currently run a Honda 2200i generator for all my power needs at the cabin we borrow while building my own. It works great, and fulfills all the needs of the our current place. I am currently planning on continuing the use of this generator in my new cabin, but also having a solar setup to supplement that usage. I have no hesitation in running the generator and burning some gasoline, I am just looking to curb my usage of it where practical and feasible. In my mind running the generator on ECO mode 80% of the time doesn't make sense when I'm just powering lights of the room I'm in, a few Exterior lights, and a TV. Based on our current usage of our borrowed cabin, we estimate we will be there roughly every other weekend, plus the occasional week long outings throughout the year.

With that said my previous experience revolves around building an inverter setup in a travel trailer with a small battery bank. It was a very simple installation, with a Samlex EVO 1212-HW inverter/charging and 4 Costco GC2 6V batteries. There was no solar elements to this installation. This provided about 6-7 days worth of power for us in the camper which more than met our needs.

I am looking to essentially recreate this setup, times two. So I'm currently looking at the Samlex EVO 2012 or 2024 HW (I am a big fan of Samlex based on my last experience), 8 GC2 batteries, and the addition of some solar panels. Obliviously the solar element is where I am lacking experience.

My goal is to not have to run the generator at night, and namely having the option of int/ext lighting for the wife to use the facilities as needed, as well as to be able to shut the generator off in the evening as we wind down our activities (So 3-4 hours of draw). Ideally the solar panels ideally take care of the bulk of the charging for the battery bank during the day, in order to be able to coast at night.

A few random questions:
  1. I am struggling to find very clear documentation about the limitations/sizes of wiring to run from my panels to the Charge controller/Samlex unit. Ideally I would like to house all my electrical components under a stairwell located on the North side of my cabin. The panels would be placed on the South side of the cabin. The cabin is 20' wide, plus 6-8' of cord for the drop into the electrical center, plus 4-8' to run from the panels into the wall. So I'm looking at a 30-46' run of wire from the panels in total. Does this seem feasible?
  2. I may be making this up, but I thought I had heard that there needs to be some way to burn off excessive power generated by the solar panels once the battery bank is fully charged. Is this true? Being that we will be away from the cabin more than we will be there I am wondering what the best option for this is (assuming it is in fact an issue and I'm not just crazy)?
  3. Assuming I am using GC2 lead batteries, I am wondering how much consideration should be given to them 'venting'. Ideally I would house them in the closet under the stairwell with the other components, however if venting is deemed unsafe there, I could relocate them just below the floor of the cabin in what will be a covered (albeit unheated) space. Below the cabin will be skirted for storage etc while still allowing for some airflow (ie: not sealed tight). It is not uncommon to see temps as low as -40F, with average temps in the teens much of the winter. Regardless of where I locate the batteries when we leave the cabin we let it go to ambient temperatures. So inevitably even if they are housed inside, they could reach temperatures well below zero. If they were to be housed inside they would warm up with the cabin interior once we arrive and before any load was put on them.
  4. Based on the temperature issue in the last question and because we never used our previous travel trailer battery bank in the winter, I am unaware of how the cold may effect the battery performance. I understand it has an impact, but am unsure as to what degree.
Also of note, I am fully aware I will have greatly diminished charging capabilities from the solar panels in the dark of winter. I am fine supplementing whatever solar charging is or is not available with running the generator to get the battery bank charged up again.

Attached are a few photos to spice it up a bit. First is the cabin we stay at while building, second two photos are of our building site for some perspective.
Thank you in advance for your input, wisdom and ideas.
-Brad
 

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brewmatic

Solar Enthusiast
Joined
Aug 6, 2021
Messages
79
According to EVO spec it requires an external soalr chrge controller if you wish to use it with solar panel. I'd use an all in one system like MPP LV2424 or something similar instead.
Wire gauge between panel and solar charge controller depends on panel configuration. Mentioned LV2424 allows solar input be from 30V to 140V. Higher voltage -> thinner wires for same wattage.
All solar charges just disconnect panels from battery when its full. You don't nee to burn any extra energy.
I'd consider to use a LiFePo battery instead of GC
 
Joined
Nov 30, 2019
Messages
12,211
The Samlex Evo's are top shelf kit.
The MPP all in ones are at least one step down IMO.
You will need a discrete solar charge controller to work with the EVO.
The EVO has a special feature that allows the inverter/charger to pass-though and supplement the solar charge controller up to 50 amps.
That is ~700 watts at 14 volts and ~1400 watts at 27 volts.
I'm guessing you won't really need that feature though.
 

chrisski

Solar Boondocker
Joined
Aug 14, 2020
Messages
3,405
I may be making this up, but I thought I had heard that there needs to be some way to burn off excessive power generated by the solar panels once the battery bank is fully charged. Is this true? Being that we will be away from the cabin more than we will be there I am wondering what the best option for this is (assuming it is in fact an issue and I'm not just crazy)?
Not True.P This is not the same as wind or hydro. THink of a solar as an on demand battery. If the charge controller does not [ull power, its nto generated. THere are some interesting threads about what to do with any power that could be created by the panels once the batteries are full, but that is not necessary.
Based on the temperature issue in the last question and because we never used our previous travel trailer battery bank in the winter, I am unaware of how the cold may effect the battery performance. I understand it has an impact, but am unsure as to what degree.
For being in Alaska, I could not see how a Lithium Build would work on a partially used cabin. I do think you need to bounce the minimum voltage off a the spec sheet. When I’ve used batteries in cold environments for portable lights, the batteries seemed to last longer, but seemed like not as much power was produced; the lights did not shine as much in the extreme cold as they did on a warm day.
================================
If you have anyway to measure true power usage like with a KilaWatt meter, that would help. I can’t see 8 GC2 batteries working well with that cabin, if four GC2 batteries meet my needs for a night getting down to about 25 F In an RV. I may have the same sized generator I turn on.
 

MichaelK

Photon Sorcerer
Joined
Mar 21, 2020
Messages
2,142
  1. I am struggling to find very clear documentation about the limitations/sizes of wiring to run from my panels to the Charge controller/Samlex unit. Ideally I would like to house all my electrical components under a stairwell located on the North side of my cabin. The panels would be placed on the South side of the cabin. The cabin is 20' wide, plus 6-8' of cord for the drop into the electrical center, plus 4-8' to run from the panels into the wall. So I'm looking at a 30-46' run of wire from the panels in total. Does this seem feasible?
You can wire your panels in series to cross long distances between the array and a MPPT charge controller. A MPPT controller acts like a transformer, converting the high raw solar voltage down to battery charging voltage, making extra charging amps out of the extra volts. In my case, I'm running four panel arrays in series at 120VDC, then the controller transforms it down to ~27-29VDC to charge the battery bank. Cheaper controller handle less voltage and less amperage than higher capacity models. You need to pay attention to what you are buying. So far you have only mentioned your inverter. What charge controller do you want to buy? The price goes up as the voltage and amperage limits go up.
  1. I may be making this up, but I thought I had heard that there needs to be some way to burn off excessive power generated by the solar panels once the battery bank is fully charged. Is this true? Being that we will be away from the cabin more than we will be there I am wondering what the best option for this is (assuming it is in fact an issue and I'm not just crazy)?
No, as Chriski says, once the controller shuts off, the current charging the battery stops. It really goes through three phases, bulk, absorption, and floating. Most of the electricity to get the depleted battery charged happens during bulk charging, the last 20% get's charged during the absorption phase, and once fully charged, the controller "floats" the battery with just enough voltage to keep it at max.
  1. Assuming I am using GC2 lead batteries, I am wondering how much consideration should be given to them 'venting'. Ideally I would house them in the closet under the stairwell with the other components, however if venting is deemed unsafe there, I could relocate them just below the floor of the cabin in what will be a covered (albeit unheated) space. Below the cabin will be skirted for storage etc while still allowing for some airflow (ie: not sealed tight). It is not uncommon to see temps as low as -40F, with average temps in the teens much of the winter. Regardless of where I locate the batteries when we leave the cabin we let it go to ambient temperatures. So inevitably even if they are housed inside, they could reach temperatures well below zero. If they were to be housed inside they would warm up with the cabin interior once we arrive and before any load was put on them.
Venting is less of a concern then you think, though I have not kept my batteries in a Alaska winter cabin. I did keep my first off-grid system in the living room for several years before upgrading to something big enough to have to be moved to the utility room. Golf-cart batteries may not be the best choice for a whole-house application. You might want to look at bigger batteries, like Trojan L-16s. This is what I have right now for my current systems. https://www.rollsbattery.com/battery/8-cs-17p/
  1. Based on the temperature issue in the last question and because we never used our previous travel trailer battery bank in the winter, I am unaware of how the cold may effect the battery performance. I understand it has an impact, but am unsure as to what degree.
Beware! Charging just one single time at below freezing can cause permanent damage to Li batteries. Pulling a load from them is not the problem. Trying to charge them after pulling a load is where the risk is. For an Alaskan application, I think you are better off with lead-acid.

Getting back to system size, have you done an itemized list yet of what you want to power? Just being around my cabin doing nothing special, I find I'm using about 3-4kWh of power per day. On orchard irrigation days, I might pull 20+kWh of power. How big a battery you'll need, and how much solar you'll need to keep them charged is going to be dependent on what you want to power, and how much solar you can expect to get in winter? I'm assuming you'll be getting about only 1-2 sunhours per day in December? That means you'll need thousands of watts of panels to just get by in winter, but will have more power than you can use in the summer. Or, a lot more generator run time in December, compared to June.
 

brewmatic

Solar Enthusiast
Joined
Aug 6, 2021
Messages
79
Beware! Charging just one single time at below freezing can cause permanent damage to Li batteries. Pulling a load from them is not the problem. Trying to charge them after pulling a load is where the risk is. For an Alaskan application, I think you are better off with lead-acid.
Yes, but you can build a thermoinsulated box for battery with thermostat controlled heating pad. It will consume very small power to keep battery above freezing temperature.
 

Bradish

New Member
Joined
Dec 16, 2021
Messages
5
Wow thanks for all the input everyone - it's fantastic to be a part of an active forum!
The Samlex Evo's are top shelf kit.
The MPP all in ones are at least one step down IMO.
You will need a discrete solar charge controller to work with the EVO.
The EVO has a special feature that allows the inverter/charger to pass-though and supplement the solar charge controller up to 50 amps.
That is ~700 watts at 14 volts and ~1400 watts at 27 volts.
I'm guessing you won't really need that feature though.
Yeah, while I don't have much experience it sure seemed like my first install with an EVO went very well. LOVED the easy to read documentation included, which I poured over multiple times and learned a lot from.
I am aware I'll need a solar charge controller, and was looking at the Samlex 30Amp controller - (SCC-30AB - https://samlexamerica.com/products/30-amp-charge-controller-scc-30ab/ ). Again this is just because I had good luck with my previous EVO, I am not married to the brand by any means if there is a better product for my application.

You can wire your panels in series to cross long distances between the array and a MPPT charge controller. A MPPT controller acts like a transformer, converting the high raw solar voltage down to battery charging voltage, making extra charging amps out of the extra volts. In my case, I'm running four panel arrays in series at 120VDC, then the controller transforms it down to ~27-29VDC to charge the battery bank. Cheaper controller handle less voltage and less amperage than higher capacity models. You need to pay attention to what you are buying. So far you have only mentioned your inverter. What charge controller do you want to buy? The price goes up as the voltage and amperage limits go up.
That idea makes sense to me in theory. Looking at the Samlex 30Amp controller (noted above) is probably where the source of my confusion began. It appears that its rate input is 12-24V looking at the specs - although there is also reference to 50V Maximum Open Circut voltage of Panel Array? Perhaps that just means it's not the right product for my installation.

Not True.P This is not the same as wind or hydro. THink of a solar as an on demand battery. If the charge controller does not [ull power, its nto generated. THere are some interesting threads about what to do with any power that could be created by the panels once the batteries are full, but that is not necessary.
No, as Chriski says, once the controller shuts off, the current charging the battery stops. It really goes through three phases, bulk, absorption, and floating. Most of the electricity to get the depleted battery charged happens during bulk charging, the last 20% get's charged during the absorption phase, and once fully charged, the controller "floats" the battery with just enough voltage to keep it at max.
Noted. Years ago I was tossing around a wind installation as it is often breezy to downright windy at the cabin site. That must have been where I picked that up and projected the thought onto all off-grid power installations. Thanks for lining me out.

For being in Alaska, I could not see how a Lithium Build would work on a partially used cabin. I do think you need to bounce the minimum voltage off a the spec sheet. When I’ve used batteries in cold environments for portable lights, the batteries seemed to last longer, but seemed like not as much power was produced; the lights did not shine as much in the extreme cold as they did on a warm day.
Beware! Charging just one single time at below freezing can cause permanent damage to Li batteries. Pulling a load from them is not the problem. Trying to charge them after pulling a load is where the risk is. For an Alaskan application, I think you are better off with lead-acid.
Not having a ton of experience with Li batteries and given the cost, this is why I have tended towards Lead acid in the design. Annecdotally I have a cellular trail camera on site to monitor security and snow depths, which is powered by 12 AA lithium batteries. I realize its a different ballpark, but I'm seeing battery life swing on the camera from 100% to 60% based on ambient temps of 30F to -10F.

And that is an interesting note I was unaware of MichaelK. I assumed pulling load would be the issue, not charging. That statement would definitely be an issue as they would likely be in some state of charge most of the time while I'm away from the cabin.

Venting is less of a concern then you think, though I have not kept my batteries in a Alaska winter cabin. I did keep my first off-grid system in the living room for several years before upgrading to something big enough to have to be moved to the utility room. Golf-cart batteries may not be the best choice for a whole-house application. You might want to look at bigger batteries, like Trojan L-16s. This is what I have right now for my current systems. https://www.rollsbattery.com/battery/8-cs-17p/
Honestly I am not very concerned about the venting, I just aware enough to make it a consideration. I'm more inclined to just house them in the closet under the stairwell and call it good. They would then have some reprieve from the cold when I'm there with the cabin warm - which is when they would be seeing load anyways. I do wonder if the heating/cooling cycles would be harmful to them if I went that route though.

I will check out the Trojan L-16's. One issue I have is that it becomes a bit hard to source specific products at times here, as we don't have many options locally for a wide variety of solar supplies. I am a 3 hour drive from the big city, which *may* have some availability for larger Trojan batteries, but I don't want to get my heart set on anything specifically until I know i can find it. For reference I'm looking at ~$200 in shipping just to get a Samlex EVO shipped to me. With the last one I got I found one person on eBay who foolishly promised free shipping, and promptly changed that after they sent me the EVO. :LOL: Sorry my guy!

If you have anyway to measure true power usage like with a KilaWatt meter, that would help. I can’t see 8 GC2 batteries working well with that cabin, if four GC2 batteries meet my needs for a night getting down to about 25 F In an RV. I may have the same sized generator I turn on.
Getting back to system size, have you done an itemized list yet of what you want to power? Just being around my cabin doing nothing special, I find I'm using about 3-4kWh of power per day. On orchard irrigation days, I might pull 20+kWh of power. How big a battery you'll need, and how much solar you'll need to keep them charged is going to be dependent on what you want to power, and how much solar you can expect to get in winter?
I am admittedly basing this on some quick back of the napkin math currently. As I currently only have the floor of the cabin complete (no walls, etc) I don't have any real world load to base this on. (I am waiting for spring to resume building, as this area typically receives 4-6ft of snow over the winter, and I didn't want to deal with that while building.)

Obviously all lighting will be LED, with about 6 interior fixtures (30W) and maybe 20 interior bulbs (10w). I see no use case where every light in the cabin would be used simultaneously. We don't use a microwave or hairdryer, etc up there so no large draw loads. The heaviest user I could forsee would be power tools, which I am more than fine with running the generator to power/supplement.

I'm assuming you'll be getting about only 1-2 sunhours per day in December? That means you'll need thousands of watts of panels to just get by in winter, but will have more power than you can use in the summer. Or, a lot more generator run time in December, compared to June.
That is probably a very accurate assumption. Beyond lighting our usage would actually decline in winter as I am less apt to do projects (tool usage) and the length of our stay at the cabin is more likely to be weekends rather than week-long endeavors. If I have to run the generator more often during the day that is fine. I'm namely looking to stay away from having to run the generator 24/7 (which we do currently) for the wife to have some lights late at night, and to power a tv etc.

As you may infer, I'm not looking for what may be the 'typical' off-grid whole house power solution. I am mainly looking for some occasional power from a battery bank, with a small solar installation to mind it while I am not there. While I don't mind spending the money to do it right, the cost needs to be equivalent to the value derived from the final product for us (if that makes sense)?
 

MichaelK

Photon Sorcerer
Joined
Mar 21, 2020
Messages
2,142
OK, let's throw out some ideas to you and see if anything sticks.

4 Trojan L-16 batteries ~400$ each, or maybe 1600$ for the four. That's not what you might have to pay way up where you are.

Epever's Tracer 8420AN controller. Can handle 200V of raw solar input, and can output up to 80A into the batteries. Maybe the 60A version.
https://www.ebay.com/itm/353663688393?hash=item5257ff9ec9:g:HqgAAOSwz6ZhOGVU 480$

Samlex EVO-2224 sine-wave inverter 1300$ at this site.

As an inverter alternative, I'd like to suggest this one, the Schneider Conext 4024, at 1600$.
This is the inverter I'm using in my workshop, and I can vouch for it's ability to start power tools. In addition to also having a charger circuit like the EVO, it is also split-phase 120/240VAC. The EVO is 120VAC only.

Six to eight 250W grid-tie panels, wired either 3S2P or 4S2P. You can put six panels on this array frame I made out of unistruts. It's a single-pole ground mount that can be rotated east to west to increase output. For my own workshop system, I selected 4S2P, with one rotating ground mount, and one fixed roof mount. According to Midnight Solar's string calculator, 4S would not surpass 200V till it reached -100 below zero.
1639777185273.png

Here's one important consideration. What would you want to leave running if you are away from the place for weeks at a time? That in part decides on the size of your system. As I mentioned above, I consume about 3-4kWh of power on a daily basis when it's just lights, TV, and some computer time. On days when I'm NOT home though, I see that the background consumption is about 1.5kWh per day, and that's with the refrigerator running. Keep in mind that the inverter itself will be consuming power just being left on. For you, that might be fine in summer, but in winter, with just 1-2 sunhours each day, you might not be able to keep up.

One strategy will be to clean out the frig, shut down the inverter, and winterize the place for when you are not there. One wild-card you will have to answer yourself is the amount of snow covering your panels. Deep snow is likely to shut the entire system down completely? Although it snows at my Sierra foothills location, I'm used to walking out and brushing off the snow in 5 minutes. That's assuming it doesn't slide off by itself before I get to it. I really have no experience dealing with arctic conditions and managing my panels for DEEP snow cover.
 

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Joined
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Samlex EVO-2224 sine-wave inverter 1300$ at this site.
Here is a better price on the EVO
 

Roswell Bob

Solar Addict
Joined
Dec 5, 2020
Messages
735
Location
Warner, NH
I'll throw a few things out there because we are almost finished with our off-grid build.

We used heated slabs on both floors of our cabin. I initially used an 80 gallon LP fired water heater to heat lower floor. We live on first floor now. . We use about 600gallons of LP to heat the lower floor- slab is not as insulated as it should be, We are no where near off-grid at this point. I have extra capacity with my solar so am looking at a small electric fired water heater to use the excess solar to heat upstairs slab. We used a lot of lowE 180 glass facing south upstairs, so it will be fairly easy to heat. I collected over 30 plate glass sliding doors and stashed in my barn. I will use for solar water heaters sometime later. I might plaster the front of house with them to heat downstairs. In any case if you can get them for free at dump they may be worth it. I may even use for a greenhouse. I figure if I can grow some weed I might be able to pay for this operation.

We surrounded the wood stove with bricks. We poured a large 8'x12' footing in the middle of the first floor. We intended to build a massive stone fireplace-both floors, but cost was out of our price range. We have wood stove on lower floor and a Heatilator fireplace upstairs. Bricks do a nice job of moderating heat. Not too hot that we have to open windows when stove is cranked, and stores quite a bit of heat so we wake up warm in the morning. We are on 40 acres, so wood is free. I may not be spending too many winters north of Florida soon so i think solar heaters may be best. If I stay up here in NH I wont want to be mucking with firewood tho.

Paraffin wax holds a lot of energy when changing from solid to liquid. If you have excess solar then it may be a benefit to melt wax with electricity when the sun is shining and let it give off heat at night when it turns solid. I haven't done math yet on cost of a system. In any case best bang for heating is not going to be electric solar.


As far as the electric thing goes you probably have all you need to know with your prior experience and many here are good resource for questions. Just watch out that you wire to code- not even sure of these DIY battery packs can ever meet code. We have a 6'x16' concrete bunker on one corner of the lower floor that I have electric in. Will never burn so insurance company will never have a beef. Put your dc and inverters outside and you have less to worry about. Easy to keep batteries warm when gone so should be simple. Watch out for lightening strikes if they are a problem up there. I lost an inverter.

As far as generators to go I don't have much to say. I had Generac that I got about 4000 hours out of before I gave away. I have Kohler now. The Kohler use hydraulic lifters so not as much farting around with. My next will probably be a 48vdc generator. In any case the electric water heater for upstairs floor and a 48v/100A charger for my cells should load up the Kohler nicely. The 14kW whole house generator uses about 2 gallons of LP/hour and is most efficient when near full load. Last thing you want to do is run a light load on one of these monsters. Like setting cash on fire.

That's all I got.

Good luck. You are well on your way and doing a nice job.
 
Last edited:

Bradish

New Member
Joined
Dec 16, 2021
Messages
5
Wow, lot to digest.
OK, let's throw out some ideas to you and see if anything sticks.

4 Trojan L-16 batteries ~400$ each, or maybe 1600$ for the four. That's not what you might have to pay way up where you are.
I have a call into this company (http://susitnaenergy.com/index.php) who seems to stock the Trojan L16P's. We'll see how much they go for.

Epever's Tracer 8420AN controller. Can handle 200V of raw solar input, and can output up to 80A into the batteries. Maybe the 60A version.
https://www.ebay.com/itm/353663688393?hash=item5257ff9ec9:g:HqgAAOSwz6ZhOGVU 480$
This is obviously where the limitations of my existing knowledge come into play. Not so much a question about this controller, but controllers in general - Would you wire this to connect directly to the battery bank, or does the output of the controller go to the inverter? I ask because at least with the Samlex it has the 'External Charger' lugs on it. Sorry, I'm sure that's an absolute rookie question.

As an inverter alternative, I'd like to suggest this one, the Schneider Conext 4024, at 1600$.
This is the inverter I'm using in my workshop, and I can vouch for it's ability to start power tools. In addition to also having a charger circuit like the EVO, it is also split-phase 120/240VAC. The EVO is 120VAC only.
I will look into it. Like I said, I'm not married to Samlex. The 240V output isn't a huge consideration for me for the time being. Not against buying to future proof, but I'll need to consider the use cases. Looks like a nice unit. Same local company referenced above appears to carry this inverter so I'll check for a quote there too.

Six to eight 250W grid-tie panels, wired either 3S2P or 4S2P. You can put six panels on this array frame I made out of unistruts. It's a single-pole ground mount that can be rotated east to west to increase output. For my own workshop system, I selected 4S2P, with one rotating ground mount, and one fixed roof mount. According to Midnight Solar's string calculator, 4S would not surpass 200V till it reached -100 below zero.
1639777185273.png
I am entirely open to panel array design/quantity, as I have zero previous experience with them. I had assumed 4-6 panels initially. Running in series for higher voltage/better transmission/smaller wire sounds fine to me, unless there are some downsides I'm unaware of.

While I know it is less than ideal, I planned on having them mounted between the 1st and 2nd story of the south side of the cabin. I am considering this location for a few reasons - namely southern exposure, ground clearance for snow, the prevailing winter wind is NE so being sheltered by the cabin would help shed wind and snow accumulation on the panels themselves. Also with the odd chance of vandals/thieves (its rare but seems to happen occasionally in the area) they would be slightly more out of reach. I can fab up mounts to change their pitch vertically fairly easy, and probably worthwhile given the large change in trajectory between summer and winter here. Horizontal changes would be tricky if mounted to the building, and I'm wondering if the cost/benefit is there or not.

Here's one important consideration. What would you want to leave running if you are away from the place for weeks at a time? That in part decides on the size of your system. As I mentioned above, I consume about 3-4kWh of power on a daily basis when it's just lights, TV, and some computer time. On days when I'm NOT home though, I see that the background consumption is about 1.5kWh per day, and that's with the refrigerator running. Keep in mind that the inverter itself will be consuming power just being left on. For you, that might be fine in summer, but in winter, with just 1-2 sunhours each day, you might not be able to keep up.

One strategy will be to clean out the frig, shut down the inverter, and winterize the place for when you are not there.
My expectations here are basically zero. Currently, when we leave the cabin everything is shut down/in including power, propane, and all water removed. If that is what needs to happen in the future that is totally fine. When we leave we clean out the fridge and turn it off (its propane anyways. Next one will likely be a dual source, but namely run on propane). We don't plan on having anything running or heat service while we're gone.

One step beyond that, and if possible (which I imagine it would be) would be to leave 1 circuit on to power two cellular trail cameras - they make AC adapters for them which would save me the trouble of buying 12 Lithium AA's every few months.

Purely dreaming as a step beyond that, I think it would be fun to have a small weather station active there to serve the recreational community in those parts. No idea what the power requirements are of that, but I can't imagine they are huge.

One wild-card you will have to answer yourself is the amount of snow covering your panels. Deep snow is likely to shut the entire system down completely? Although it snows at my Sierra foothills location, I'm used to walking out and brushing off the snow in 5 minutes. That's assuming it doesn't slide off by itself before I get to it. I really have no experience dealing with arctic conditions and managing my panels for DEEP snow cover.
Yeah, I suspect there will always be some level of that. Because the sun is so low on the horizon in the winter for us, I suspect my panel angle will help limit the amount of snow built up on the panels themselves. Total snow depth was also one reason I was considering mounting them mid wall on the side of the cabin, as opposed to a ground mount.

Thanks for all your feedback. You're making me burn calories thinking through all of this :LOL:
 

Bradish

New Member
Joined
Dec 16, 2021
Messages
5
That sounds like quite the interesting operation you've got going there Bob!
As far as the electric thing goes you probably have all you need to know with your prior experience and many here are good resource for questions. Just watch out that you wire to code- not even sure of these DIY battery packs can ever meet code. We have a 6'x16' concrete bunker on one corner of the lower floor that I have electric in. Will never burn so insurance company will never have a beef. Put your dc and inverters outside and you have less to worry about. Easy to keep batteries warm when gone so should be simple. Watch out for lightening strikes if they are a problem up there. I lost an inverter.
I think I will be set in terms of wiring - fortunately there is no code to meet in this neck of the woods! I work in an industrial plant which has 6 electricians on staff, so I can readily ping them with questions. Unfortunately none of them are into solar, but they keep me out of trouble with general electrical practices - so they're still a great resource. Lightening is pretty rare for us here, only happening about once a year so I tend not to pay it any mind.

With the DC elements, Im thinking of placing it inside, perhaps in an enclosure with a clear lexan face or something.
 

dev96

New Member
Joined
Dec 20, 2021
Messages
1
Bradish,

Looking at the big picture in what your end goal is, I would suggest approaching your cabin's electrical as you would an RV. That is the approach that I have migrated to over the years in maintaining several off-grid backwoods setups and it has saved me a lot of heartaches.

Your generator (I have a EU3000) is an asset that you are incorporating into your function but want to have the option of using it... or not using it. Therefore your PV system should be considered more of a battery maintenance provision than a stand-alone power provider.

My biggest issues over the years have been component and "human" failures that bite when least expected and almost always resulted in needing something I didn't have on hand. Unattended off-grid systems are just highly failure prone so work WITH that knowledge vs against it. For those and many other reasons, I have learned to keep things very simple and use what can easily be replaced. Because keeping a few off-the-shelf spare parts on hand in remote locations can be the difference between having a great time or a complete nightmare.

Focus on a small PV setup with a very simple MPPT controller. What I mean by that is 100 watts of panels max (id go smaller if it wasn't Alaska) and a cheap 30 amp controller from somewhere like Amazon. ($40)... Then simply buy two (or three) of them vs one $150 unit. Because in the woods, two is one and one is none. Trust me they work fine and 97% of the time what has killed ones that I've lost (including the high dollar ones) was something totally unrelated to "quality".

Going the path of "simplistic and cheap" (not poorly designed) is oftentimes WAY overlooked in DIY solar... There is no such thing as bulletproof in electronics in the da'woods!!!

Pick up a 55W RV load center ($150) and use that to wire in your whole cabin. this will give you several advantages in a turn-key style. Easy, neat wiring, a dual voltage system that works off of PV and generator, (inverter if you want) but also charges your batteries rapidly. I've found that to be best where remote visiting goes because I can't tell you the number of times I've shown up to guests leaving something on, a weather-related issue, or something else going wrong that resulted in dead batteries. Being able to plug in and run my generator and have it simply fix everything wrong at that moment has saved me many weekends.

Put in a 12V main disconnect that kills off the load center, this prevents issues with things that can be left on by accident... As long as you can get yourself (more so others) to turn off the main disconnect on the way out the door you will save yourself issues!!!

Consider tossing all of the 12V ATC fuses in your load center and putting in auto-resetting circuit breakers... You go to plug in an automotive type 12V plug to blow up the ole air mattress and accidentally cause a short at the plug. To me this isn't a big deal, you just change the fuse. OTOH I had a friend completely melt out a set of 8 gauge wires trying to perform the same simple feat (with a screwdriver)... Auto resetting ATC breakers are everyone's best off-grid friend.

If you can pick up all 12V items (TV, laptop power adapter, etc) you can spend less time running your generator all together when things are working right.

For batteries, I suggest using a D8 gel cell. I've given up on trojan or regular lead acid-based batteries, too many issues with longevity and especially fumes! The sulfur ammonia smell that develops keeping them indoors will eventually take over and takes YEARS to go away. Compared to the best lithium deep cycle made today you are going to pay about $900 for 100AH whereas a gell D8 will be the same cost for 250AH. The abuse factor they withstand cant be understated!!! I have 5 in service that have been drained below 6 volts (more than once and left there for MONTHS). Every time I swear they are done, every time they bounce back... All 5 are 13+ years old and I'm still using them.

If you need or want any help with your project please let me know and I will be glad to design or layout diagrams and do watt/amp load calculations for you. I've learned that prudent planning and getting everything into CAD drawings along the way makes for easier builds and maintenance down the road!
 

curmudgeinn

New Member
Joined
Jan 17, 2022
Messages
4
Yes, but you can build a thermoinsulated box for battery with thermostat controlled heating pad. It will consume very small power to keep battery above freezing temperature.
Howdy all -

New to the forum, looking to source the vast array of knowledge. Been reading some of the material in the Newby and FAQ section, but not finding everything I'm looking for.

Figured I would start a thread to ask a few questions and document the install process once I get there.

I am building a cabin (nearly a house) in Alaska. This is in a recreational area, considered semi-remote, and definitely off-grid. If anyone is interested I am documenting that build process on the Small Cabin forums here: https://www.small-cabin.com/forum/6_10671_0.html . I won't rehash everything that has gone into that, but try to focus on the solar portion here.

Design theory:
I currently run a Honda 2200i generator for all my power needs at the cabin we borrow while building my own. It works great, and fulfills all the needs of the our current place. I am currently planning on continuing the use of this generator in my new cabin, but also having a solar setup to supplement that usage. I have no hesitation in running the generator and burning some gasoline, I am just looking to curb my usage of it where practical and feasible. In my mind running the generator on ECO mode 80% of the time doesn't make sense when I'm just powering lights of the room I'm in, a few Exterior lights, and a TV. Based on our current usage of our borrowed cabin, we estimate we will be there roughly every other weekend, plus the occasional week long outings throughout the year.

With that said my previous experience revolves around building an inverter setup in a travel trailer with a small battery bank. It was a very simple installation, with a Samlex EVO 1212-HW inverter/charging and 4 Costco GC2 6V batteries. There was no solar elements to this installation. This provided about 6-7 days worth of power for us in the camper which more than met our needs.

I am looking to essentially recreate this setup, times two. So I'm currently looking at the Samlex EVO 2012 or 2024 HW (I am a big fan of Samlex based on my last experience), 8 GC2 batteries, and the addition of some solar panels. Obliviously the solar element is where I am lacking experience.

My goal is to not have to run the generator at night, and namely having the option of int/ext lighting for the wife to use the facilities as needed, as well as to be able to shut the generator off in the evening as we wind down our activities (So 3-4 hours of draw). Ideally the solar panels ideally take care of the bulk of the charging for the battery bank during the day, in order to be able to coast at night.

A few random questions:
  1. I am struggling to find very clear documentation about the limitations/sizes of wiring to run from my panels to the Charge controller/Samlex unit. Ideally I would like to house all my electrical components under a stairwell located on the North side of my cabin. The panels would be placed on the South side of the cabin. The cabin is 20' wide, plus 6-8' of cord for the drop into the electrical center, plus 4-8' to run from the panels into the wall. So I'm looking at a 30-46' run of wire from the panels in total. Does this seem feasible?
  2. I may be making this up, but I thought I had heard that there needs to be some way to burn off excessive power generated by the solar panels once the battery bank is fully charged. Is this true? Being that we will be away from the cabin more than we will be there I am wondering what the best option for this is (assuming it is in fact an issue and I'm not just crazy)?
  3. Assuming I am using GC2 lead batteries, I am wondering how much consideration should be given to them 'venting'. Ideally I would house them in the closet under the stairwell with the other components, however if venting is deemed unsafe there, I could relocate them just below the floor of the cabin in what will be a covered (albeit unheated) space. Below the cabin will be skirted for storage etc while still allowing for some airflow (ie: not sealed tight). It is not uncommon to see temps as low as -40F, with average temps in the teens much of the winter. Regardless of where I locate the batteries when we leave the cabin we let it go to ambient temperatures. So inevitably even if they are housed inside, they could reach temperatures well below zero. If they were to be housed inside they would warm up with the cabin interior once we arrive and before any load was put on them.
  4. Based on the temperature issue in the last question and because we never used our previous travel trailer battery bank in the winter, I am unaware of how the cold may effect the battery performance. I understand it has an impact, but am unsure as to what degree.
Also of note, I am fully aware I will have greatly diminished charging capabilities from the solar panels in the dark of winter. I am fine supplementing whatever solar charging is or is not available with running the generator to get the battery bank charged up again.

Attached are a few photos to spice it up a bit. First is the cabin we stay at while building, second two photos are of our building site for some perspective.
Thank you in advance for your input, wisdom and ideas.
-Brad
What part of Alaska are you in? I am north of Talkeetna.
 
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