diy solar

diy solar

Brown bear destroyed our yurt powered by Yeti 3000, so I'm designing solar for a cabin & a bit lost

2. How to put an auto-start generator into the mix so that it also can charge the battery automatically after talking with the SCC (or some other device)? For example, it should only kick the generator on to charge the 48V battery bank if it's above freezing and if there is no PV coming into the 48V batteries. I know from discussions in this thread, it can be wired into an inverter/charger to charge the battery, but how will it know not to deliver a charge if it's below freezing or if PV power is being received?

Slowly, slowly, I feel like I'm learning...
I don't know enough about the Orion to give any useful advice, and I unfortunately have almost 0 experience with generators.

Your BMS should shut off charging if it's below freezing, but that should be used as a secondary failsafe against freezing, not a primary (I don't trust the low temp protection on most BMS's). I would recommend using a separate thermostat and relay to shut off, or turn on, charging.

I use one of these ( https://www.amazon.com/dp/B073W425LW/ref=cm_sw_r_cp_apa_fabc_HCV3Q31XSS7BBFNYD0CM ) to shut off PV input in the event of low temperatures. It's connected to a relay that physically cuts the power from the panels, so even if the BMS protection fails, it has no way to charge. I would imagine that you could use something similar to control a generator.
 
I don't know enough about the Orion to give any useful advice, and I unfortunately have almost 0 experience with generators.

Your BMS should shut off charging if it's below freezing, but that should be used as a secondary failsafe against freezing, not a primary (I don't trust the low temp protection on most BMS's). I would recommend using a separate thermostat and relay to shut off, or turn on, charging.

I use one of these ( https://www.amazon.com/dp/B073W425LW/ref=cm_sw_r_cp_apa_fabc_HCV3Q31XSS7BBFNYD0CM ) to shut off PV input in the event of low temperatures. It's connected to a relay that physically cuts the power from the panels, so even if the BMS protection fails, it has no way to charge. I would imagine that you could use something similar to control a generator.
Good stuff. I'll need to figure out what can talk to the generator so that the generator isn't running and wasting gas to provide charge to a battery that won't take it because it's too cold. Ideally something, SCC or otherwise, should be turning it on and off only when it's not freezing and when PV isn't supplying power and when the bank gets to a preset level of discharge or something. Bonus points if it could connect to the internet and get a sun forecast, do the math, and decide to turn the generator or not based on expected sun.
 
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Good stuff. I'll need to figure out what can talk to the generator so that the generator isn't running and wasting gas to provide charge to a battery that won't take it because it's too cold. Ideally something, SCC or otherwise, should be turning it on and off only when it's not freezing and when PV isn't supplying power and when the bank gets a preset level of discharge or something. Bonus points if it could connect to the internet and get a sun forecast, do the math, and decide to turn the generator or not based on expected sun.
I've seen people use raspberry pi's to network everything together, but it's definitely beyond my skill level. It's completely possible to connect all of the components together and change the parameters to have them run of the solar system at optimal settings, as well as control generators.

I think that soon there will be complete automation systems for solar setups, but for now, it's mostly all diy.


 
For example, it should only kick the generator on to charge the 48V battery bank if it's above freezing and if there is no PV coming into the 48V batteries.
You would be much better off placing the batteries in a heated room.
LiFePo is not like lead-acid and can be placed inside.
Think about it, it would have been stupid being without power just because it is too cold outside. In Alaska! :unsure:
 
You would be much better off placing the batteries in a heated room.
LiFePo is not like lead-acid and can be placed inside.
Think about it, it would have been stupid being without power just because it is too cold outside. In Alaska! :unsure:
All batteries will be inside, but it will only be heated when we are there. When we're not there, we still need some amount of power.

I'll use a single 12V Relion-LT (low temperature) battery that will charge and discharge down to -4F that will be fed power from a subset of PV, the 48V battery bank, and from a generator that auto starts. So I shouldn't be without power when it's cold outside/inside (when we leave for a day or longer, it gets ambient inside the cabin). When we're at the cabin, we fire up the wood stove, and then the 48V battery bank will also be able to accept a charge because they will be in the heated cabin at that point.

We don't have a way to heat the 48V batteries when we're not there though. We will get 800W of power a day roughly in the darkest/coldest days and if we're not at the cabin, we need a battery that will heat itself from the PV which is why we'll go with a Relion-LT for a subset of the system, so that it can power the electric fence and bear security stuff.
 
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I've seen people use raspberry pi's to network everything together, but it's definitely beyond my skill level. It's completely possible to connect all of the components together and change the parameters to have them run of the solar system at optimal settings, as well as control generators.

I think that soon there will be complete automation systems for solar setups, but for now, it's mostly all diy.


Using Pis is a great idea. I've built a few things with Pis so that's up my alley if I can't find an out of the box solution.
 
We don't have a way to heat the 48V batteries when we're not there though.
A styrofoam box and some silicone heating pads, hooked to the same thermostat I recommend earlier should work.

I have a small battery that I leave in my trailer most of the year, and it's wrapped up in foam, and has a heating pad on each side. (There is a picture of it half-done in my post history) When it hits 35°f, it kicks on and warms it up to 45°. The battery is small, so the heating pads are pretty small as well, but they only use ~12 watts each, and that little bit of heat goes a LONG way in a well insulated box.

According to my Govee thermometer, If the box starts at about 65°f, it takes about 2 days of below freezing temperatures to cool it down to the point it needs to turn on the pads. The pads stay on for about 20 minutes, and the box is warm for at least another day. Good insulation is definitely the key though.

I didn't use the specific company below, but if I had the need to heat an expensive system, reliably and safely, I would use the nice ISO and UL listed ones, rather than amazon's recommended.

 
All batteries will be inside, but it will only be heated when we are there. When we're not there, we still need some amount of power.

I'll use a single 12V Relion-LT (low temperature) battery that will charge and discharge down to -4F that will be fed power from a subset of PV, the 48V battery bank, and from a generator that auto starts. So I shouldn't be without power when it's cold outside/inside (when we leave for a day or longer, it gets ambient inside the cabin). When we're at the cabin, we fire up the wood stove, and then the 48V battery bank will also be able to accept a charge because they will be in the heated cabin at that point.

We don't have a way to heat the 48V batteries when we're not there though. We will get 800W of power a day roughly in the darkest/coldest days and if we're not at the cabin, we need a battery that will heat itself from the PV which is why we'll go with a Relion-LT for a subset of the system, so that it can power the electric fence and bear security stuff.
I consider that being really risky. In an Alaskian winter, you will not have enough solar power available to waste as heat.
You may -at an average, theoretically- get 800Wh of power a day on snow-free panels, which is ridiculously low, absolutely not enough to keep your stuff above freezing, and surely not in a worst case situation.
Generators auto-start... or not!
You really should consider some propane/oil burner (maybe a car standby heater) to keep your stuff above freezing in a well insulated power room.
Will you get an alarm if something gets wrong? How long does it then take for someone to intervene?
 
I consider that being really risky. In an Alaskian winter, you will not have enough solar power available to waste as heat.
You may -at an average, theoretically- get 800Wh of power a day on snow-free panels, which is ridiculously low, absolutely not enough to keep your stuff above freezing, and surely not in a worst case situation.
Generators auto-start... or not!
You really should consider some propane/oil burner (maybe a car standby heater) to keep your stuff above freezing in a well insulated power room.
Will you get an alarm if something gets wrong? How long does it then take for someone to intervene?
What's the risk? I have 800Wh a day of PV in the darkest days of winter and a generator backup to power an electric fence and some USB powered security devices. In an Alaskan winter I always run the very real risk of not getting enough PV and there is the risk that the generator backup will break down, and then the electric fence won't be charged. But not getting enough PV isn't likely to happen except Nov-Jan when the sun is the lowest and the bears should be sleeping by then. If that happens then we'll just be counting on the cabin design to keep the bears out (which was our primary design consideration). But IF there isn't enough PV and IF the generator has an issue and the electric fence goes unpowered and IF the bears aren't sleeping, then we'll just have to accept that risk and hope that our cabin design keeps them out.

The way the Relion-LT battery works is if the PV is producing below freezing, the power from PV is diverted to a 3amp heater that heats the cells up to temp and when they are above freezing the PV power will then start charging the cells. If the PV isn't producing, the battery won't be heating. A real waste would be heating the battery up during times when the PV isn't producing and there is no juice to charge it, or if the generator backup has already filled the battery up. In that situation, the power used to heat it would be wasted because there is no PV to charge it anyway, or because it's full and doesn't need juice from the generator.

If there was some auto propane/oil system that I could use to heat up the batteries I would certainly be interested in that. I'm not sure if I can buy heating oil and transport it up in the ATV or not though. I don't know much about heating oil although lots of people use it. My impression is that it's not really portable but I don't know. But that system, open flame, would be the biggest risk given that I live in a place that has earthquakes and I'm in the middle of a tinderbox forest. But there are some safety features of propane systems that could mitigate that risk, but I haven't seen a propane system that will kick on or off automatically when needed to maintain heat. I have seen one that will maintain a certain temp/setting and runs automatically but I don't need it heating the place in the middle of the night because nobody is there to enjoy the heat and the batteries can't take a charge (unless from the generator).

At this point I'll use a Relion-LT battery which will heat itself when it's getting PV and then will accept a charge, and hopefully that will be tied into a generator backup such that generator supplied power (auto-kicked on) will heat the LT battery and then accept the charge from the generator. That should be enough to supply power to the electric fence and bear security devices when we're not there. I would imagine that would keep everything powered for weeks even in the dead of winter but who knows.

When we are there, we'll simply heat the place up with the wood stove and then the 48V bank can take PV power and generator power.

When we're not there, there will be nobody to intervene. We live in the middle of nowhere and I do not want to be locked to the place and unable to travel because I need to manually heat the place so that a battery can take a charge. The RELiON LT with generator backup should fit the bill and heat its cells (rather than a whole battery or a whole room) to keep the security systems powered while we're away using the tiny amount of PV available and using the generator that is controlled on/off by a SCC or some other device.
 
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That is definitely something we want to look into for the future for sure. Thanks!
It would probably be for the best. I'm assuming it can get pretty windy up there and Alaska isn't exactly famed for its sun.

My concern with wind would be the effect of ice and snow on the turbine but that's the risk.

Managed to find this: https://www.fieldlines.com/

They have a LOT of discussion around wind.



Has a lot of good wind info.
 
That is definitely something we want to look into for the future for sure. Thanks!
Just be aware of the limitations, without the proper investment in good (and apparently very tall) equipment, you may be disappointed.


Also, I install and maintain automation systems on swimming pools. With some modifications, you could relatively easily make one of them control a generator, based on temperature, and they are very reliable. It's really just a board with a bunch of temperature probes that can control relays and actuators. The link below is for automation of a greenhouse, but I think that's more relevant for your cabin.

 
Just be aware of the limitations, without the proper investment in good (and apparently very tall) equipment, you may be disappointed.


Also, I install and maintain automation systems on swimming pools. With some modifications, you could relatively easily make one of them control a generator, based on temperature, and they are very reliable. It's really just a board with a bunch of temperature probes that can control relays and actuators. The link below is for automation of a greenhouse, but I think that's more relevant for your cabin.

Thanks! I've looked into wind and it definitely has some limitations. It's something I'll look into in the future after I get solar installed but there are certainly some issues with it.

I appreciate the info. At this point for the 12V Relion-LT battery (low temp) I just want the generator to auto kick on and charge the battery when the battery gets to a level of discharge (perhaps 20% remaining), and when PV isn't producing. For the 48V battery, I'd want the other generator to come on when it's above freezing, gets down to 20%, and the PV isn't producing. I would think some piece of solar equipment, whether the SCC or an inverter, would be able to do this.
 
Just be aware of the limitations, without the proper investment in good (and apparently very tall) equipment, you may be disappointed.


Also, I install and maintain automation systems on swimming pools. With some modifications, you could relatively easily make one of them control a generator, based on temperature, and they are very reliable. It's really just a board with a bunch of temperature probes that can control relays and actuators. The link below is for automation of a greenhouse, but I think that's more relevant for your cabin.

I brought it up largely due to his location being poorly suited to solar enough that secondary options might be useful is all.
 
With the system so far my main questions are:

1. Should I use a DC-DC charger to charge the 12V battery from the 48V bank, or an MPPT?

2. How to get the generators in the mix so they are kicked on to charge the batteries only when the SOC gets down to 20% and they are not getting PV from the array (and, in the case of the 48V system, when it's above freezing)?

Most recent system schematic attached

That's a very strange layout. Many of those panels will be in a very sub-optimal position.

Have you considered lawn racks or anything like that?
 
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That's a very strange layout. Many of those panels will be in a very sub-optimal position.

Have you considered lawn racks or anything like that?
True statement. Our property, terrain, and trees make the whole place sub optimal for solar! But the yurt we've been living in is WAY less optimal than this spot and solar was still good enough for the two of us except in the winter when we'd have to run the generator. That was just 1600W of solar panels in a much worse location. This location should be much better especially with so many more panels.

We don't have a lawn, we have a forest. This cabin on the 45' x 60' deck that is elevated 10' above the ground is going to be our best bet. Especially as the cabin will give us some more height on top of that.
 
So a few folks here have mentioned that inverters not only invert power from the batteries into AC for the cabin, but also an inverter/charger can charge the batteries too. This guy has a Victron system and has his inverter/charger connected to his generator so when he turns on the generator it supplies power for charging his batteries (I assume in addition to any PV coming in and while also inverting power for his house). Now if I can find an inverter that talks to the SCC and knows when to auto kick on the generator I'll be set.


In a more recent video he replaced his inverter/charger with a Victron Multiplus though. TheColorist has been nice enough to provide me with some great recommendations and he recommended the Victron Multiplus II for our application. I need to study up on that and see if it talks to the charge controllers and can turn the generator on or off. That would be a huge plus if so. Also, it would be nice to turn that inverter off when we leave the cabin so that the 18W draw in idle doesn't deplete batteries that aren't be used while we're away.

 
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