diy solar

diy solar

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

The switch to 24V will definitely help with reducing the number of charge controllers since you only need half the charging current (amperage) you would need for 12V.

If you are considering installing Victron Multiplus or Quattro inverter/chargers, depending on the model, each one has a charging capacity of between 50A-120A (models 2000VA-5000VA). Rather than let that charger go unused unless you're running the generator, you could AC-Couple the Multiplus/Quattro with a PV inverter.

Here is a quick diagram I modified from Victron to represent your 24V system. You'll several other things (possibly auto-transformer unless you use 2x inverters etc) but it will give you an idea.

1614546044450.png

That's just one configuration and again it's missing several things. Another would be to use the AC-Out 2 on the Multiplus/Quattro for the PV inverter and that's likely what I would recommend. I didn't get to review the entire thread to make a complete layout but there is a chance this will be cheaper for you than running several charge controllers. Many PV inverters have multiple MPPT trackers so you can vary your strings size or types of panels per string. If you're using SolarEdge with optimizers, that will help with varied light per panel and mixing panel types. Will be much less wiring to deal with as well, since your string voltage(s) can be just shy of 600V.

The wired AC sensor is to prevent power from pushing back to the generator but there are other ways to do that as well that might be easier to setup.
 
Hello and sorry to hear about your yurt.

Recommend 24V battery system strongly.

built in heater on relion sounds hard to beat for simple

building a battery enclosure with 4” of insulation and putting a small heating pad on the bottom (cold ground) is an option many on the forum have considered or built. be sure to get type that prevents ice, not a water heater. they are thermostatically controlled which means no complicated electronic heat control needed. eg 100 dollar on foam insulation might go further than 100 dollar on specialized battery with internal heater.

edit: links
insulation example: https://www.homedepot.com/p/Thermas...-Rigid-Foam-Insulation-Board-613010/100573703
heater pad example: https://www.amazon.com/Facon-Holding-Trailer-Automatic-Thermostat/dp/B01MT9EUG9

only mentioning this because it could lower battery cost and lower SCC cost a lot with a little preparation

i’ve run a small 12V outdoor DIY solar system for a few year now (1KWh storage, 0.6KW panels) and even at this tiny scale, my robust victron blue solar 150/30 mppt cannot utilize the entire solar potential. right now 30 amp * 14.1V = 423W max. after upgrade, 30 amp * 28.2V = 846W max.

that thing wasn’t cheap either. planning to switch from 12V to 24V very soon to capture more solar power (using frey 100Ah cells and JBD/overkillsolar BMS).

anyways going to 24V will give you double the charger per dollar in a sense

x dollars per output amp of SCC capacity
 
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Sorry to hear about the bear. Are you putting these batteries outside? I keep my batteries inside, WA state, not nearly as cold as Alaska, but still close to 0F outside through winter, inside never below 50, don't even need to worry about the freezing. If you are keeping them inside the cabin you could go with just about any LFP battery with a low temp shutoff, incase you loose heat inside for a spell. Battle Born, heck even SimpliPhi, are far cheaper then the planned Relion and they come in 24 and 48v configurations.

Winter panels up there is a great idea, they will produce during summer also, not as much, but they will and it is the winter when you need the power the most, as you clearly already know.

If you already have the 100w Renogy panels, use them, no problems.
 
Sorry to hear about the bear. Are you putting these batteries outside? I keep my batteries inside, WA state, not nearly as cold as Alaska, but still close to 0F outside through winter, inside never below 50, don't even need to worry about the freezing. If you are keeping them inside the cabin you could go with just about any LFP battery with a low temp shutoff, incase you loose heat inside for a spell. Battle Born, heck even SimpliPhi, are far cheaper then the planned Relion and they come in 24 and 48v configurations.

Winter panels up there is a great idea, they will produce during summer also, not as much, but they will and it is the winter when you need the power the most, as you clearly already know.

If you already have the 100w Renogy panels, use them, no problems.
Yes, we will put them inside but we won't always be at the cabin with the wood stove going so it will get down to freezing in there and we need them to be able to take a charge and to provide power because it will power our security systems to keep the bears away which, when we're gone, is when we need them the most. Battle Born requires manually flipping a heat switch on and off so that's not going to work for our application.

I'm very curious about winter panels. When you say winter panels are you referring to the angle and direction of panels or are you referring to a certain kind of panel designed for winter?
 
Hello and sorry to hear about your yurt.

Recommend 24V battery system strongly.

built in heater on relion sounds hard to beat for simple

building a battery enclosure with 4” of insulation and putting a small heating pad on the bottom (cold ground) is an option many on the forum have considered or built. be sure to get type that prevents ice, not a water heater. they are thermostatically controlled which means no complicated electronic heat control needed. eg 100 dollar on foam insulation might go further than 100 dollar on specialized battery with internal heater.

edit: links
insulation example: https://www.homedepot.com/p/Thermas...-Rigid-Foam-Insulation-Board-613010/100573703
heater pad example: https://www.amazon.com/Facon-Holding-Trailer-Automatic-Thermostat/dp/B01MT9EUG9

only mentioning this because it could lower battery cost and lower SCC cost a lot with a little preparation

i’ve run a small 12V outdoor DIY solar system for a few year now (1KWh storage, 0.6KW panels) and even at this tiny scale, my robust victron blue solar 150/30 mppt cannot utilize the entire solar potential. right now 30 amp * 14.1V = 423W max. after upgrade, 30 amp * 28.2V = 846W max.

that thing wasn’t cheap either. planning to switch from 12V to 24V very soon to capture more solar power (using frey 100Ah cells and JBD/overkillsolar BMS).

anyways going to 24V will give you double the charger per dollar in a sense

x dollars per output amp of SCC capacity
Thanks very much for this info! I'm going to run some math and see how much money I can save with the 24V system.
 
So here is my redesigned system which I am hoping will cut down the 9 charge controllers needed from my 12V only system into only 4 charge controllers needed. Many thanks in advance for corrections on my understanding of what is possible and any recommendations on how to do it better!

The key area I need to get educated on is the capability of DC-DC chargers.

This system is comprised of two battery banks. The first, the black rectangle, is a single 12V Relion LT (low temp) battery. The second, the two purple rectangles, is two 12V non-LT Relion batteries wired in series for a 24V system.

There are 4 PV arrays shown as yellow rectangles. A temperature correction of 1.23 was used for my area. All panels are Renogy 320W panels (40.1 VOC).

There are 4 Victron charge controllers shown with red, orange, and blue circles. There is a Honda generator shown with a green circle.

- WPV is the winter array and consists of two strings of 5 x 320W panels wired in parallel which should produce 203V max to the SCC and make 53.4 amps available to the Victron 250/60 SCC for charging.

- SPV1 is the primary summer array and consists of two series strings of 5 x 320W panels wired in parallel which should produce 203V max to the SCC and make 53.4 amps available to the Victron 250/60 SCC for charging.

- SPV2 is the secondary summer array and consists of one string of 4 x 320W panels wired in series which should produce 198V max to the SCC and make 26.7 amps available to the Victron 200/30 SCC for charging.

- IPV is the interim season array and consists of two series strings of 4 x 320W panels wired in parallel which should produce 198V max to the SCC and make 53.4 amps available to the Victron 200/60 SCC for charging.

The IPV array's Victron 200/60 SCC will charge the 12V battery bank. That battery bank will use a DC-DC charger -- shown as a brown rectangle-- (if it's possible to have a 12V battery bank charge a 24V battery bank) to charge the 24V battery bank when the 12V battery bank is full and the SCC continues to deliver power.

The other arrays will have their SCCs all charge the 24V battery bank. That battery bank will use a DC-DC charger -- shown as a brown rectangle -- to charge the 12V battery bank when the 24V battery bank is full.

A Honda generator will be tied into the IPV Victron SCC and will be turned on automatically to charge the 12V battery bank when it's not full and when the SCC is not producing power.

* The intent of this system is to primarily charge the 12V battery because when we are away from the cabin, all the batteries will get as cold as -4F and we need that battery to power our bear security systems while we're away.
 

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Please clarify the generator connection. I’m a little confused about generator to solar charge controller concept.

The overall design seems really nice.

Perhaps consider the use of a DPDT switch/relay between both of the DC-DC converters. That way can ensure only one converter runs at a time. Trying to help avoid the cyclic charging potential of lost energy where they just charge each other a lot back and forth. Like connect the 24->12 converter to Normally Closed terminal and the 12->24 converter to Normally Open

Of course if the DC DC converters were configured properly then having a relay might not really be needed..

Thanks for the update and I hope others can chime in with more advice.
 
Please clarify the generator connection. I’m a little confused about generator to solar charge controller concept.

The overall design seems really nice.

Perhaps consider the use of a DPDT switch/relay between both of the DC-DC converters. That way can ensure only one converter runs at a time. Trying to help avoid the cyclic charging potential of lost energy where they just charge each other a lot back and forth. Like connect the 24->12 converter to Normally Closed terminal and the 12->24 converter to Normally Open

Of course if the DC DC converters were configured properly then having a relay might not really be needed..

Thanks for the update and I hope others can chime in with more advice.
Thanks for the DPDT switch recommendation. I need to study up on what that is and also on the operation of the DC-DC chargers to know how that part will work. I think the DC-DC charger gets wired up as a dump load somehow although I'm not sure if I can have multiple SCCs dumping their load into the same string of DC-DC chargers or if I'd need separate DC-DC chargers for each SCC.

More to your point I need to figure out how they work in relation to each other. I would think that a SCC wouldn't be dumping a load to the SCC unless its battery bank was already full, so in order for both batteries to be getting a DC-DC charge, both batteries would have to be full. That would be an interesting situation, not sure if DC-DC chargers know not to charge when a battery is already full or not.

The generator, I am told, will wire into a charge controller and I am assuming will be kicked on when the SCC detects the battery isn't full and isn't getting any power from the PV array. This is something else I need to flesh out though. We bought a kit for the generator that was originally designed to work with a mid nite solar SCC but we never did set it up (but we were told the mid nite solar would start the generator and turn it off when it wasn't getting enough solar and the battery wasn't full). We just have the components (which we bought before we learned about the Yeti 3000). It was part of our original starter kit system but we decided to go with the Yeti instead. I need to get into the weeds to make sure it will do what I need it to do.

I obviously still have a whole lot of learning to do. Thanks again for the input.
 
I apologize in advance for pointing this out but the amperage ratings on the charge controllers are based on output amps, not input amps. This is because the maximum amperage will be on the low voltage side of the controller. It's a completely understandable/common mistake, not all the literature is perfectly clear.

Here is some math breakdown to show:

WPV = 5 x 320W x 2 = 3,200W

3,200W / 24V nominal (low side) = 133A

You would need a 133A controller for that array. Or multiple controllers.

SPV1 = 5 x 320W x 2 = 3,200W

3,200W / 24V nominal (low side) = 133A

SPV2
= 4 x 320W = 1,280W

1,280W / 24V nominal (low side) = 53.3A

IPV
= 4 x 320W x 2 = 2,560W

2,560W / 24V nominal (low side) = 106A

I figured IPV at 24V but I have a comment as to why below. For 12V, just double the amperage.

The non-temp-compensated PV input voltage/current for the arrays would be as follows (VOC/ISC):

WPV = 203V 20.16A

SPV1 = 203V 20.16A

SPV2 = 198V 10.08A

IPV = 198V 20.16A

You may already be aware of this but with that number of charge controllers you'll either want to get an Octo GX (10 VE.Direct ports) or preferably VE.Can versions of the BlueSolar/SmartSolar charge controllers.

You have valid concerns with configuring the DC-DC controllers and exchanging power between buses. IMHO your best bet would be to connect all your panels and SCC controllers to a central 24V bus. Your 24V batteries and inverters would also be connected to this bus. Then use a DC-DC to shunt power from the master 24V bus to your 12V battery/inverter. This allows all available PV power to either system at all times. The only limitation would be the size of your DC-DC or even multiple DC-DC controllers. This would eliminate any issues with conflicting DC-DC or eddy currents/oscillation etc.

For DC-DC from the 24V bus to the 12V bus, you can technically use a BlueSolar/SmartSolar MPPT (or several). This would actually be good because the charging will be much more precise than a generic DC-DC or even the Orion series. The reason is that your GX on the 12V system can control the charging precisely through Distributed Voltage Current Control (DVCC). This includes temp comp (remote temp sense), voltage comp (remote voltage sense) and SOC status from a SmartShunt/BMV.

If your batteries on the 24V are full, you always have the option (and IHMO I would recommend this) to cascade them. AC-Out 2 on the 24V to AC-In on the 12V. This means that if the 12V inverter becomes overloaded for any reason, it will connect to the 24V inverter and it will assist.

With Victron it's typically recommended to have your genstart handled by your GX device. Only the GX has full view of the system and can handle things such as "quiet time" etc.

Also if your generator is connected to the AC input of the 24V inverter, it will pass through to the 12V inverter and both will charge at the same time while all loads on both inverters are carried by the generator. You'll need to configure a maximum AC-Input limit on the 12V inverter to below the AC-In relay max on the 24V. The precise amperage you want to set will depend on a variety of factors.

I would gladly create a schematic for you of this configuration but unfortunately I've run out of time at the moment. If you'd like one though let me know.

Battle Born requires manually flipping a heat switch on and off so that's not going to work for our application.
According to BattleBorn's literature, they have both automated heating pads (appears that they would work with any battery system) and the new heated BB10012 (Link). I have not used BattleBorn batteries so perhaps I'm missing something though and it's no automated.

If the generic pads work on any battery GC2 or similar battery, that could be an option even for a DIY bank or another brand's battery. Could possibly eliminate your 12V needs altogether?
 
I apologize in advance for pointing this out but the amperage ratings on the charge controllers are based on output amps, not input amps. This is because the maximum amperage will be on the low voltage side of the controller. It's a completely understandable/common mistake, not all the literature is perfectly clear.

Here is some math breakdown to show:

WPV = 5 x 320W x 2 = 3,200W

3,200W / 24V nominal (low side) = 133A

You would need a 133A controller for that array. Or multiple controllers.

SPV1 = 5 x 320W x 2 = 3,200W

3,200W / 24V nominal (low side) = 133A

SPV2
= 4 x 320W = 1,280W

1,280W / 24V nominal (low side) = 53.3A

IPV
= 4 x 320W x 2 = 2,560W

2,560W / 24V nominal (low side) = 106A

I figured IPV at 24V but I have a comment as to why below. For 12V, just double the amperage.

The non-temp-compensated PV input voltage/current for the arrays would be as follows (VOC/ISC):

WPV = 203V 20.16A

SPV1 = 203V 20.16A

SPV2 = 198V 10.08A

IPV = 198V 20.16A

You may already be aware of this but with that number of charge controllers you'll either want to get an Octo GX (10 VE.Direct ports) or preferably VE.Can versions of the BlueSolar/SmartSolar charge controllers.

You have valid concerns with configuring the DC-DC controllers and exchanging power between buses. IMHO your best bet would be to connect all your panels and SCC controllers to a central 24V bus. Your 24V batteries and inverters would also be connected to this bus. Then use a DC-DC to shunt power from the master 24V bus to your 12V battery/inverter. This allows all available PV power to either system at all times. The only limitation would be the size of your DC-DC or even multiple DC-DC controllers. This would eliminate any issues with conflicting DC-DC or eddy currents/oscillation etc.

For DC-DC from the 24V bus to the 12V bus, you can technically use a BlueSolar/SmartSolar MPPT (or several). This would actually be good because the charging will be much more precise than a generic DC-DC or even the Orion series. The reason is that your GX on the 12V system can control the charging precisely through Distributed Voltage Current Control (DVCC). This includes temp comp (remote temp sense), voltage comp (remote voltage sense) and SOC status from a SmartShunt/BMV.

If your batteries on the 24V are full, you always have the option (and IHMO I would recommend this) to cascade them. AC-Out 2 on the 24V to AC-In on the 12V. This means that if the 12V inverter becomes overloaded for any reason, it will connect to the 24V inverter and it will assist.

With Victron it's typically recommended to have your genstart handled by your GX device. Only the GX has full view of the system and can handle things such as "quiet time" etc.

Also if your generator is connected to the AC input of the 24V inverter, it will pass through to the 12V inverter and both will charge at the same time while all loads on both inverters are carried by the generator. You'll need to configure a maximum AC-Input limit on the 12V inverter to below the AC-In relay max on the 24V. The precise amperage you want to set will depend on a variety of factors.

I would gladly create a schematic for you of this configuration but unfortunately I've run out of time at the moment. If you'd like one though let me know.


According to BattleBorn's literature, they have both automated heating pads (appears that they would work with any battery system) and the new heated BB10012 (Link). I have not used BattleBorn batteries so perhaps I'm missing something though and it's no automated.

If the generic pads work on any battery GC2 or similar battery, that could be an option even for a DIY bank or another brand's battery. Could possibly eliminate your 12V needs altogether?
Man, I made that same mistake again after Forbisher at length corrected me the first time. That's embarrassing. I took a few days off to do some family stuff and then sat down and made the same mistake yet again!

Thanks for pointing that out, and thanks for all that great info on the DC-DC charging and such. I'm going to dig into this in the morning and I very much appreciate the help.
 
Yes, we will put them inside but we won't always be at the cabin with the wood stove going so it will get down to freezing in there and we need them to be able to take a charge and to provide power because it will power our security systems to keep the bears away which, when we're gone, is when we need them the most. Battle Born requires manually flipping a heat switch on and off so that's not going to work for our application.

I'm very curious about winter panels. When you say winter panels are you referring to the angle and direction of panels or are you referring to a certain kind of panel designed for winter?
The angle and direction of the panels is what I mean by winter panels. My panels in WA are adjustable but I have to do it manually every 3-4 months if I want to and it isn't... easy. I understand what you are saying, you aren't at the cabin for sometimes several days or longer? Ya that would make it hard to keep the place warm. That does make for a sticky situation, the most I would leave my system for is a week and that is if I know I have good sun on at least one of those days. 1600 watts isn't enough to 'set and forget' about the system either.
 
You have valid concerns with configuring the DC-DC controllers and exchanging power between buses. IMHO your best bet would be to connect all your panels and SCC controllers to a central 24V bus. Your 24V batteries and inverters would also be connected to this bus. Then use a DC-DC to shunt power from the master 24V bus to your 12V battery/inverter. This allows all available PV power to either system at all times. The only limitation would be the size of your DC-DC or even multiple DC-DC controllers. This would eliminate any issues with conflicting DC-DC or eddy currents/oscillation etc.
I can't pretend to know much about this, but the reason I'm hesitant to have all the PV go to the 24V system (and from there to the 12V battery) because when I need it the most, it will be -4F inside my cabin and the SCCs will prevent sending a charge to the 24V batteries (because they won't be low temp batteries since I can't have a 24V system with the LT batteries).

I am interested in the idea of warming up a 24V battery bank with the heating pad and putting them in an insulated box. I'm a bit hesitant to do this, no doubt due to my ignorance, because I don't want to damage them or start a fire and burn down our life savings and start a forest fire. I'm guessing that wouldn't happen because I *think* the batteries would refuse to take a charge if the heating pad wasn't working property or didn't heat the individual cells enough, but I'm very risk averse when it comes to fire. Probably my ignorance and I'll study up on it more for sure because if I could have a single 24V system that would make this whole project so much simpler and cheaper.

For now though, I am planning on the RELiON LT (low temp) battery so that it will charge when the cabin is down to -4F (heating the individual battery cells) so that it will power the bear security systems and the electric fence while the 24V system won't accept a charge (which is no big deal because if we're not there warming up the cabin then we won't be drawing off the 24V battery bank anyway).

But I may very well not be understanding something so apologies in advance!
 
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If your batteries on the 24V are full, you always have the option (and IHMO I would recommend this) to cascade them. AC-Out 2 on the 24V to AC-In on the 12V. This means that if the 12V inverter becomes overloaded for any reason, it will connect to the 24V inverter and it will assist.
For the single LT (low temp) 12V battery, I wasn't intending to have an inverter (but I may come to the conclusion that I need one as I learn more). I was hoping to have it power the electric fence and some USB powered devices and perhaps use a DC-DC charger to charge the 24V batteries. I *think* all that can be powered with DC only and I'm probably going to drop the DC-DC charger for charging the 24V batteries and just have DC-DC from the 24V charging the 12V system.
 
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Little cleaner updated schematic.
 

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It is just a bigger panel with a smaller % of that being the frame. The main driver is price. The bigger panels tend to be a lower $/Watt. It's also less effort to mount. 4 fasteners regardless of panel size for the most part.

PVWatts will not give you SCC recommendations. It just simulates your system for you in terms of annual and monthly solar harvest or usable AC power if you've applied an efficiency factor.

Your SCC is dictated by your charging current, which depends on battery voltage. Your 5400W array would need:

5400W/12V = 450A
5400W/24V = 225A
5400W/48V = 112A

Those numbers are conservative, and you can fall a little short of them. You can also split your array into multiple facings to spread your power more evenly over the day and keep your peak current lower.
In Alaska you might use a 50% divisor on the PV watts and possibly even less, you will practically never get 1000W irradiance / m².
Since you have to calculate off-grid I would even calculate with 30%.
 
In Alaska you might use a 50% divisor on the PV watts and possibly even less, you will practically never get 1000W irradiance / m².
Since you have to calculate off-grid I would even calculate with 30%.

Curious.

PV Watts takes globe location into consideration and includes average influence of weather, i.e., it knows you'll never get 1000W/m^2. Why would you cut it in half arbitrarily?

Selecting Fairbanks, optimal annual tilt would be about 65°:

1615239553020.png

Do you really think you'll only get 1/2 of the listed values?
 
For my part I just covered our planned cabin with about as much solar as I could (there is room for more on the very top of the structure but that will only get sun during the shoulder season and summer due to terrain, trees, and snow but will be plenty during summer). I haven't looked into what I can expect to get really since I'm just trying to max it out knowing that I'll be fighting for every drop of sunlight in the winter.

I've updated my schematic. I'm still fuzzy on how our Honda EU3000is generator will wire into the charge controller to charge the 12V battery, but I am guessing it will involve this modification to the generator (or something similar): http://www.generator-line.com/~shop/eu3w2-two-wire-start/389143/
 

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The generator produces AC output. In a typical configuration, the inverter is an inverter/charger meaning that it can receive AC input and provide charging to the battery. If your inverter does not have this function, you will need an AC-DC converter to charge the batteries.

You would wire the output of the generator to the AC input of the inverter/charger.
 
Here is a look at t
The generator produces AC output. In a typical configuration, the inverter is an inverter/charger meaning that it can receive AC input and provide charging to the battery. If your inverter does not have this function, you will need an AC-DC converter to charge the batteries.

You would wire the output of the generator to the AC input of the inverter/charger.
Ah, I didn't realize the inverter also charged the battery. That's good to know. I guess I may have to get an inverter (or just a charger since I'm not planning on running any AC loads from the 12V) to connect the generator to the 12V battery. Will the inverter/charger know "the battery isn't full and no PV is coming in, so start the generator?"
 
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