Solar Panel and Inverter/Battery Recommendations for small solar installation and 1KW generator

Hi all.

About a year ago I posted about this application here.  We're finally at the point of pulling the trigger, and was hoping the forum would be kind enough to lend some advice before I buy anything.

With respect to solar panels, I'm looking for something cost effective in terms of watts/$, but I probably don't want to go as far as ordering panels from alibaba.  These will be installed on the roof of my garage, and I'm looking for somewhere between 3 and 5 KW total.  Panels that also create hot water are intriguing, but I've heard horrible stories about them failing catastrophically if the pump stops working, so unless that problem has been solved, I'll probably avoid those.

With respect to the inverter/smart battery bank, I was recommended "an outback vfxr in any wattage/voltage combination or a radian 4048".  Are those still the way to go, or has something changed in the last year?  I presume I'll need overcharge protection from my generator to the battery bank, and I don't believe that any of the inverter/battery banks do that out of the box.  I'm not familiar with these products, and so I could use some advice, assuming they aren't all pretty much the same thing.

Lastly, the generator will produce a lot of waste heat.  (It actually runs on heat (see original post), but isn't very efficient overall).  In the winter that's a good problem to have, but I'm not sure what to do about it in the summer.  The chimney can be insulated, but a lot of the heat will come off the engine itself.  There's a waterjacket that can be used to pull that heat away and make the engine more efficient at the same time, but what should I exhaust it to?  Something like a cooling tank which I install outside of the garage?

Thanks in advance.

Solar Panel = 4KW = 16x 250W  (Daily Production = 4KW x 4H = 16KWH)
Charge Controller = 48V x 100A = 4.8KW
Battery Bank Storage = 48V x 400AH = 19.2KWH (some folks recommend having 3day of storage aka 48KWH)
Inverter = 4KW = 48V x 85A (you will probably need 2 of these for 240V split-phase AC)

Inverter+Charger
https://www.wholesalesolar.com/1440335/wholesale-solar/power-centers/outback-radian-gs8048a-01-8-000-watt-with-fm80-power-center
https://www.wholesalesolar.com/1440348/wholesale-solar/power-centers/outback-radian-gs4048a-4-000-watt-with-fm80-power-center
Solar Panel
https://www.wholesalesolar.com/1930029/canadian-solar/solar-panels/canadian-solar-315-watt-module-black-mono-perc-mc4-cs3k-315ms-35mm-frame-solar-panel
Battery
https://www.wholesalesolar.com/solar-battery-banks
Best Ready to go grid-tied kit
https://www.wholesalesolar.com/1893213/wholesale-solar/complete-systems/3.84-kw-gridtied-battery-backup-solar-system-with-outback-power-center-and-12x-heliene-320-panels

S Bengi wrote:Solar Panel = 4KW = 16x 250W  (Daily Production = 4KW x 4H = 16KWH)
Charge Controller = 48V x 100A = 4.8KW
Battery Bank Storage = 48V x 400AH = 19.2KWH (some folks recommend having 3day of storage aka 48KWH)
Inverter = 4KW = 48V x 85A (you will probably need 2 of these for 240V split-phase AC)

Inverter+Charger
https://www.wholesalesolar.com/1440335/wholesale-solar/power-centers/outback-radian-gs8048a-01-8-000-watt-with-fm80-power-center
https://www.wholesalesolar.com/1440348/wholesale-solar/power-centers/outback-radian-gs4048a-4-000-watt-with-fm80-power-center
Solar Panel
https://www.wholesalesolar.com/1930029/canadian-solar/solar-panels/canadian-solar-315-watt-module-black-mono-perc-mc4-cs3k-315ms-35mm-frame-solar-panel
Battery
https://www.wholesalesolar.com/solar-battery-banks
Best Ready to go grid-tied kit
https://www.wholesalesolar.com/1893213/wholesale-solar/complete-systems/3.84-kw-gridtied-battery-backup-solar-system-with-outback-power-center-and-12x-heliene-320-panels

If I wanted to save some money, could I skip the batteries and just grid-tie both the solar panels and the generator using the same inverter?  It seems it would be more efficient overall compared to storing energy in a battery for later use.  I realize that I will be paying retail for the energy and selling it back at more like wholesale, but considering the cost of battery banks, I feel like it would take a long time to break even based solely on the difference

I've seen some videos online about making your own battery bank, and from what I recall it's a lot cheaper than a pre-built solution and not hard to do.

https://www.wholesalesolar.com/1892012/wholesale-solar/complete-systems/solar-sky-4.14-kw-grid-tied-solar-system-with-sma-and-12x-astronergy-solar-345-panels
Yes the ready to go system above works with or without battery. And can be grid-tied or off grid.

Here is a 4KW ready to go kit for only $6,000 (grid tie only)
https://www.wholesalesolar.com/1892012/wholesale-solar/complete-systems/solar-sky-4.14-kw-grid-tied-solar-system-with-sma-and-12x-astronergy-solar-345-panels
Ready to go kit with later tie in for battery and generator to make it off grid capable ($8,200)
https://www.wholesalesolar.com/1823833/wholesale-solar/complete-systems/3.78-kw-storage-ready-grid-tied-solar-system-with-outback-power-and-12x-canadian-solar-315w-panels


If you are not going to have a battery setup, then I recommend a sunnyboy 5KW $1500 grid-tie contoller/inverter. It has 3 independent DC inputs with built in DC shutoff.
For $3700 you can get a 5KW outback one that allows you to connect a regular generator and battery bank at a later date.
https://www.wholesalesolar.com/2550550/outback-power/inverters/outback-power-skybox-sbx5048-120-240-inverter

You mention that you have a 1KW generator. Can you describe the output of that generator.
Is it AC or DC, what is the output voltage and current?
If it is AC is it pure sine wave?
Is it running 24/7 or winter only or only when the power goes out?
What type of fuel does said generator use

EDIT:
It seems like this is the generator that you are using
https://seftonmotors.com/products/the-melvin-package
It seems that your generator outputs DC
12V (or 24V with special request) and 1200W. So 12V x 100A or 24V x 50A

You can add a DC-DC step up converter.
12V to 120VDC and maybe interface that with the 3rd independent DC input on the SunnyBoy Controller/Inverter.

For a second lets simplify and forget about the solar aspect of your system.
How does one go about tie-ing your 12v, 1200W generator that you want to feed into the grid and get paid for?
Will it need a wind controller/inverter that will break, or a solar controller that will just idle, or is it a hydro controller that needs a dump load.

Lets say it will idle safely similar to a solar controller. One would need to bring the voltage up from 12V to 100V/250V. Because that is the min DC voltage for most grid tie system.

Now if we go back to having both solar and this "weird generator" both being grid tied. Does both the Solar leg and the 'weird Generator" leg both get their own controller/inverter.
Or can they both connect to the same controller/inverter, but on different independent string inputs.

Except the generator will not operate like solar panel where there will be dip in voltage as current request increase.
So we would have to treat it like a wind turbine and thus give it, it's own controller/inverter.

I know how to get up an off grid system with a separate solar panel and wind/hydro sub-system both charging a common battery system. But how does this work for a grid tied system. And how will it react when there is a power outage and there is no battery to store energy but there is a power/voltage feedback, how about the utility workers isn't the system suppose to shutdown to protect them and prevent a lawsuit/jail time.

S Bengi wrote:
If you are not going to have a battery setup, then I recommend a sunnyboy 5KW $1500 grid-tie contoller/inverter. It has 3 independent DC inputs with built in DC shutoff.
For $3700 you can get a 5KW outback one that allows you to connect a regular generator and battery bank at a later date.
https://www.wholesalesolar.com/2550550/outback-power/inverters/outback-power-skybox-sbx5048-120-240-inverter

You mention that you have a 1KW generator. Can you describe the output of that generator.
Is it AC or DC, what is the output voltage and current?
If it is AC is it pure sine wave?
Is it running 24/7 or winter only or only when the power goes out?
What type of fuel does said generator use

EDIT:
It seems like this is the generator that you are using
https://seftonmotors.com/products/the-melvin-package
It seems that your generator outputs DC
12V (or 24V with special request) and 1200W. So 12V x 100A or 24V x 50A

You can add a DC-DC step up converter.
12V to 120VDC and maybe interface that with the 3rd independent DC input on the SunnyBoy Controller/Inverter.

Thanks again for the reply.

With respect to the generator input on the SBX5048, I'm looking through the manual and it appears to only take AC generators.  Where could I hook up a 24VDC generator?

There's quite a price jump from inverters with battery inputs to those without them.  The outback is almost 2.5 times the cost of the SunnyBoy.  Is it just the battery support driving the price?  Overall the Outback seems pretty neat.

There's quite a price jump from inverters with battery inputs to those without them.  The outback is almost 2.5 times the cost of the SunnyBoy.  Is it just the battery support driving the price?  Overall the Outback seems pretty neat.

The outback system is really a 4-in-1 device (generator interface, battery charger, battery inverter and solar panel controller-converter). The sunnyboy is just 1 device (solar panel controller-converter)

Where could I hook up a 24VDC generator?

As far as I can tell to have a grid tie solar + generator (wind/hydro/hydrocarbon/biomass) a battery bank is needed in the middle otherwise you can only have one, not both.
or

https://www.wholesalesolar.com/1823833/wholesale-solar/complete-systems/3.78-kw-storage-ready-grid-tied-solar-system-with-outback-power-and-12x-canadian-solar-315w-panels
So in addition to the ready to go outback kit above you will also need a battery + generator to battery interface.
It can be the tiniest battery bank of just one as long as the voltage is 48V. The interface is just a charge controller (24v input, 48v output).
While I was able to find 24v to 48v step charge controllers, they dont seem to support 50A (Genasun GV-Boost controllers) and victron dc-dc https://www.victronenergy.com/dc-dc-converters

[quote=S Bengi]For a second lets simplify and forget about the solar aspect of your system.
How does one go about tie-ing your 12v, 1200W generator that you want to feed into the grid and get paid for?
Will it need a wind controller/inverter that will break, or a solar controller that will just idle, or is it a hydro controller that needs a dump load.

Lets say it will idle safely similar to a solar controller. One would need to bring the voltage up from 12V to 100V/250V. Because that is the min DC voltage for most grid tie system.

Now if we go back to having both solar and this "weird generator" both being grid tied. Does both the Solar leg and the 'weird Generator" leg both get their own controller/inverter.
Or can they both connect to the same controller/inverter, but on different independent string inputs.

Except the generator will not operate like solar panel where there will be dip in voltage as current request increase.
So we would have to treat it like a wind turbine and thus give it, it's own controller/inverter.

I know how to get up an off grid system with a separate solar panel and wind/hydro sub-system both charging a common battery system. But how does this work for a grid tied system. And how will it react when there is a power outage and there is no battery to store energy but there is a power/voltage feedback, how about the utility workers isn't the system suppose to shutdown to protect them and prevent a lawsuit/jail time.[/quote]

As to the last part, my understanding is that grid tie systems must automatically stop feeding the grid if grid power is lost.  Is it more complicated than that?

I'm not sure what the engine is most like, other then a regular genset.  One difference might be that it starts slower.

I looked over the heat engine specs. Am I correct that it comes with a pma head from Missouri solar? If that is the case you would have to run it into it's own charge controller. Missouri solar has an interesting one but probably not code compliant. If you want a charge controller that is code compliant the midnite solar classic  is a good choice. Usually you pair it with a dump load but since you can feed the grid you dont need to as the grid is your dump load.
If your heat engine is putting out dc from that pma head you will need to use a battery based grid tie inverter like the radian listed above. You could also go for the solarc which is a newer unit and has all the function you would need and all the components are built into one unit making it more cost effective.
You are going to get a lot of diy advice on grid connecting but the regulations are quite strict so you need code compliant gear with all the utility approved disconnects and safeties. The digital utility meters can detect current flow direction and any unauthorized flow can land you in a load of trouble. Forget options like induction engines or plug in grid tie inverters those guerrilla solar days are gone.  Please let me know if I'm wrong about the heat engine power head...
Cheers,  david

The manufacturer of the heat engine generator might be able to give you a 48V output. (they already offer a 12v and 24v setup).
The original manufacturer actually offers a 48V version. https://mwands.com/freedom-pmg-permanent-magnet-generator

So all you would need is:
1KW Generator (48V) https://seftonmotors.com/collections/frontpage/products/the-melvin-package
Generator Charge Controller (48V) https://mwands.com/xantrex-c40-hybrid-wind-turbine-solar-panel-charge-controller
Battery (48V) https://www.wholesalesolar.com/9580101/simpliphi/batteries/simpliphi-phi-3.8-kwh-48v-lfp-battery
Solar Grid-Tied Kit https://www.wholesalesolar.com/1823833/wholesale-solar/complete-systems/3.78-kw-storage-ready-grid-tied-solar-system-with-outback-power-and-12x-canadian-solar-315w-panels


$2,400 Generator 1KW (Combined Heat, Hot Water and Electricity device from tri-fuel incl. wood)
$140 Generator Charge Controller (48V)
$3,000 Battery (48V)
$8,200 Solar Grid-Tied Kit (can support 6KW of solar vs just 4KW)

Brian Church wrote:Panels that also create hot water are intriguing, but I've heard horrible stories about them failing catastrophically if the pump stops working, so unless that problem has been solved, I'll probably avoid those.

The neatest, low-tech hot water heater I have ever seen was a simple black metal tank mounted on a pole above the roof of a summer cottage. I was told that it worked well during the warm months, but I never had the chance to test the water myself, so to speak. I was also told that this was a common old-school solution to heating water at the summer community I was visiting. Having always imagined that a solar water heater had to be high-tech, this idea struck me as remarkable at the time but now seems quite obvious. The hot water would, of course, vary in temperature and would require some sort of expansion tank and/or pressure release system, so don't try this without professional supervision!

As for panels, I am quite happy with my 8 Panasonic 325 watt panels with Enphase IQ7X Microinverters. They do a pretty good job of powering my efficient home if you average the electricity over the year. Since we are in a city with a reliable power grid, we use the grid as our battery backup, with the meter running backwards when we are creating more power than we need (net metering). I am watching batteries come down in price and thinking that it might not be long before there are affordable, plug-in versions of battery backup systems to rival portable gas generators. When I bought my system, however, I did the math and realized that a portable gas generator was a more affordable backup system in our location.

We use natural gas for on-demand heat and hot water.

Good luck with your system!

I think the simpliphi batteries are overkill for this application just a small agm bank woud be more affordable. I don't think the C40 charge controller would not do it since the heat engine is going to fluctuate in output so an mppt option would be better. The classic is affordable if you pair it with the agms instead of the lithium I believe...
CHeerrs,  David

Seeing as how battery backup isn't really needed yet.
Four 12V battery for $100 each could easily be use for a total of $400 vs $3,000. I completely agree

For the classic are you think this $1300 setup https://mwands.com/midnite-classic-200-mppt-all-in-one-charge-controller-board-for-solar

S Bengi wrote:Seeing as how battery backup isn't really needed yet.
Four 12V battery for $100 each could easily be use for a total of $400 vs $3,000. I completely agree

For the classic are you think this $1300 setup https://mwands.com/midnite-classic-200-mppt-all-in-one-charge-controller-board-for-solar

that is a neat assembly but the breakers could be included in the radian enclosure and a bridge rectifier would be required as well...

David Baillie wrote:I looked over the heat engine specs. Am I correct that it comes with a pma head from Missouri solar? If that is the case you would have to run it into it's own charge controller. Missouri solar has an interesting one but probably not code compliant. If you want a charge controller that is code compliant the midnite solar classic  is a good choice. Usually you pair it with a dump load but since you can feed the grid you dont need to as the grid is your dump load.
If your heat engine is putting out dc from that pma head you will need to use a battery based grid tie inverter like the radian listed above. You could also go for the solarc which is a newer unit and has all the function you would need and all the components are built into one unit making it more cost effective.
You are going to get a lot of diy advice on grid connecting but the regulations are quite strict so you need code compliant gear with all the utility approved disconnects and safeties. The digital utility meters can detect current flow direction and any unauthorized flow can land you in a load of trouble. Forget options like induction engines or plug in grid tie inverters those guerrilla solar days are gone.  Please let me know if I'm wrong about the heat engine power head...
Cheers,  david

Hi, I believe you're correct about the powerhead.  Does code compliance matter if the goal is for a battery bank to sit between the generator and the grid?

S Bengi wrote:The manufacturer of the heat engine generator might be able to give you a 48V output. (they already offer a 12v and 24v setup).
The original manufacturer actually offers a 48V version. https://mwands.com/freedom-pmg-permanent-magnet-generator

So all you would need is:
1KW Generator (48V) https://seftonmotors.com/collections/frontpage/products/the-melvin-package
Generator Charge Controller (48V) https://mwands.com/xantrex-c40-hybrid-wind-turbine-solar-panel-charge-controller
Battery (48V) https://www.wholesalesolar.com/9580101/simpliphi/batteries/simpliphi-phi-3.8-kwh-48v-lfp-battery
Solar Grid-Tied Kit https://www.wholesalesolar.com/1823833/wholesale-solar/complete-systems/3.78-kw-storage-ready-grid-tied-solar-system-with-outback-power-and-12x-canadian-solar-315w-panels


$2,400 Generator 1KW (Combined Heat, Hot Water and Electricity device from tri-fuel incl. wood)
$140 Generator Charge Controller (48V)
$3,000 Battery (48V)
$8,200 Solar Grid-Tied Kit (can support 6KW of solar vs just 4KW)

I can ask him to change it or refund it and buy my own.  I preordered this system some time ago (incidentally the price was a bit lower), but I was waiting to ship it for some upstream logistical reasons.

Karl Treen wrote:
We use natural gas for on-demand heat and hot water.

Good luck with your system!

Thanks for the reply.  It seems like trying to add solar and hot water in the same system from the get-go is over-engineering it in my case.  While the property has forced hot water radiator heat, it may actually be easier to try and capture waste heat from the engine.

David Baillie wrote:I think the simpliphi batteries are overkill for this application just a small agm bank woud be more affordable. I don't think the C40 charge controller would not do it since the heat engine is going to fluctuate in output so an mppt option would be better. The classic is affordable if you pair it with the agms instead of the lithium I believe...
CHeerrs,  David

David Baillie wrote:

S Bengi wrote:Seeing as how battery backup isn't really needed yet.
Four 12V battery for $100 each could easily be use for a total of $400 vs $3,000. I completely agree

For the classic are you think this $1300 setup https://mwands.com/midnite-classic-200-mppt-all-in-one-charge-controller-board-for-solar

that is a neat assembly but the breakers could be included in the radian enclosure and a bridge rectifier would be required as well...

Thanks again, I will do my homework on that asap.

Your 1KW DC generator/wind turbine, has a few options for a MPPT charge controller.
$520 Midnite Wind Kid https://mwands.com/midnite-kid-marine-charge-controller
$640 Midnite Classic https://mwands.com/midnite-solar-classic-mppt-charge-controller-150
$1300 Midnite Classic Code Compliant Kit https://mwands.com/midnite-solar-classic-150-mppt-all-in-one-charge-controller-board-for-solar
$1670 Midnite Classic Full Kit https://mwands.com/midnite-classic-mppt-wind-turbine-charge-controller-board

Instead of buying the kit for $1300/$1670 you could probably cobble some shutoff for cheaper, but with the unit you could install a real wind turbine in the future easily, assuming it makes sense for your location.

A few questions about your 1KW generator package.
Does it come with:
1) Firebox (what does it burn and not burn propane, natural gas, oil, bio-fuel, wood-rocket stove. BTU=50,000 aka 14.6KW, 900F)
2) Water Jacket/Heat Loss (upto 11KW....About 100gal of DHW... or radiator space heat/radiant floor heating... how much of can really be captured)
3) Turbine/Engine (1.2KW, where ΔT=600F, P=24psi, efficiency=8%)
4) Generator (1KW, efficiency=6.8%)
5) Exhaust (T=150F, 2.4KW)

How many hours per day will you run it aka how many KW will you produce a day/month/year.
Is the main purpose of your generator to heat a greenhouse, domestic hot water, winter space heating, or just to produce electric from your extra fuel/waste stream/biochar production.

Where the seller states that 1000W is possible it looks like only 300W is the norm. Do you see 300W being the norm for you or will you optimize/pressurize your setup.

In a way they basically created a heat driven(temperature deferential) wind tunnel and stick a wind turbine in it. Which is pretty cool. Is that how you view their design.

S Bengi wrote:Your 1KW DC generator/wind turbine, has a few options for a MPPT charge controller.
$520 Midnite Wind Kid https://mwands.com/midnite-kid-marine-charge-controller
$640 Midnite Classic https://mwands.com/midnite-solar-classic-mppt-charge-controller-150
$1300 Midnite Classic Code Compliant Kit https://mwands.com/midnite-solar-classic-150-mppt-all-in-one-charge-controller-board-for-solar
$1670 Midnite Classic Full Kit https://mwands.com/midnite-classic-mppt-wind-turbine-charge-controller-board

Instead of buying the kit for $1300/$1670 you could probably cobble some shutoff for cheaper, but with the unit you could install a real wind turbine in the future easily, assuming it makes sense for your location.

A few questions about your 1KW generator package.
Does it come with:
1) Firebox (what does it burn and not burn propane, natural gas, oil, bio-fuel, wood-rocket stove. BTU=50,000 aka 14.6KW, 900F)

It can burn wood, gas, or waste oil.  I have a steady supply of WVO.

S Bengi wrote:
2) Water Jacket/Heat Loss (upto 11KW....About 100gal of DHW... or radiator space heat/radiant floor heating... how much of can really be captured)

My understanding is that it won't get water up to the 80-90 C needed for providing standalone heating via radiators.  That said, some baseboard or a radiator would at least take the edge off the area not directly by the exhaust pipe, and increase efficiency by cooling the water.

S Bengi wrote:
3) Turbine/Engine (1.2KW, where ΔT=600F, P=24psi, efficiency=8%)
4) Generator (1KW, efficiency=6.8%)
5) Exhaust (T=150F, 2.4KW)

It comes with the generator.

S Bengi wrote:
How many hours per day will you run it aka how many KW will you produce a day/month/year.
Is the main purpose of your generator to heat a greenhouse, domestic hot water, winter space heating, or just to produce electric from your extra fuel/waste stream/biochar production.

The purpose is to create heat and electricity for a garage and a loft space.  I'm not sure if it won't create too much heat in the summer, even with the stack and firebox insulated.  In the winter, I'm hoping to run it 18 hours per day, or more.  I've been thinking about other ways I might be able to use the waste heat, aside from what comes out of the water jacket,

S Bengi wrote:
Where the seller states that 1000W is possible it looks like only 300W is the norm. Do you see 300W being the norm for you or will you optimize/pressurize your setup.

In a way they basically created a heat driven(temperature deferential) wind tunnel and stick a wind turbine in it. Which is pretty cool. Is that how you view their design.

Pretty much, although the internal mechanics aren't driven by the combustion updraft.  Instead it's the expansion and contraction of a working fluid (air) in a sealed system.  I'm hoping to be able to get above 800 W consistently.

Thanks for the suggestions above.  Since my last post I was looking at the Sol-Ark 8K, for the inverter.  If I'm understanding, the battery control unit would charge the batteries independently of the grid-tie inverter.  However, the grid-tie inverter would also need to interface with the batteries, so am I correct in assuming the battery bank will have two inputs for charging?

Thanks again.

Yes two charge inputs. You would have to talk to solark to see if one of the mppt inputs can be used for the pma. Maybe... that would save on gear and it's already wired in and comes with the unit... missouri solar could probably tweak a charge controller just for your application I've found them very helpful.

Ahh, it's a sterling engine.

I called Sol-Ark, and they also said I should use a separate charge controller.

Although I'm having trouble finding an example at the moment, I've come across inverters which have multiple DC inputs for solar.  Presuming I had a 48V generator, couldn't I the 2nd input for the generator?

No you cant add both solar and motor/generator to the same charge controller. Even though it has two Solar DC string input.

Brian Church wrote:I called Sol-Ark, and they also said I should use a separate charge controller.

Although I'm having trouble finding an example at the moment, I've come across inverters which have multiple DC inputs for solar.  Presuming I had a 48V generator, couldn't I the 2nd input for the generator?

what solark probably meant is their charge controllers are not made for taking the input from a pma. Now we know...

I noticed that you mentioned that you cant find a charge controller for your generator. Check the quote below for quite a few of them.
And yes you will need two SEPARATE charge controller the solar panels will plug into the Sol-ark and the generator into the Midnite.

S Bengi wrote:Your 1KW DC generator/wind turbine, has a few options for a MPPT charge controller.
$520 Midnite Wind Kid https://mwands.com/midnite-kid-marine-charge-controller
$640 Midnite Classic https://mwands.com/midnite-solar-classic-mppt-charge-controller-150
$1300 Midnite Classic Code Compliant Kit https://mwands.com/midnite-solar-classic-150-mppt-all-in-one-charge-controller-board-for-solar
$1670 Midnite Classic Full Kit https://mwands.com/midnite-classic-mppt-wind-turbine-charge-controller-board

S Bengi wrote:I noticed that you mentioned that you cant find a charge controller for your generator. Check the quote below for quite a few of them.
And yes you will need two SEPARATE charge controller the solar panels will plug into the Sol-ark and the generator into the Midnite.

S Bengi wrote:Your 1KW DC generator/wind turbine, has a few options for a MPPT charge controller.
$520 Midnite Wind Kid https://mwands.com/midnite-kid-marine-charge-controller
$640 Midnite Classic https://mwands.com/midnite-solar-classic-mppt-charge-controller-150
$1300 Midnite Classic Code Compliant Kit https://mwands.com/midnite-solar-classic-150-mppt-all-in-one-charge-controller-board-for-solar
$1670 Midnite Classic Full Kit https://mwands.com/midnite-classic-mppt-wind-turbine-charge-controller-board

S Bengi,

Thanks for your continued help.  I'm seeing some good deals on inverters.  For instance, the Solaredge 10K Watt model can be had for under $1000 right now.

Given that there's a battery between the sources of generation and the inverter now, and this can't be all integrated into the inverter purchase, does it make sense to spend a bit less on the inverter and more on the charge controllers?

My understanding is that some charge controllers can be linked together in order to provide a single interface for monitoring, and presumably play a bit nicer than simply wiring them in parallel.

The inverter, on the other hand, doesn't even need to be that smart.  Some basic charging/usage profiles should be enough.

The solar edge inverter will not work for this use case.
It will not talk to a 48v or 24v or 12v battery bank. They are 100% grid tied a few support 450v LG Chem batteries.
So you will have to stick with the existing line up of 2 charge controllers
For PV panels it is  Sol-Ark
For the generator Midnite Classic

S Bengi wrote:The solar edge inverter will not work for this use case.
It will not talk to a 48v or 24v or 12v battery bank. They are 100% grid tied a few support 450v LG Chem batteries.
So you will have to stick with the existing line up of 2 charge controllers
For PV panels it is  Sol-Ark
For the generator Midnite Classic

I heard from a vendor that they don't recommend the Sol-Ark 8K inverter as they claim it has problems with certain loads.

That leaves the 12K model, which is quite a bit of money.

Are you saying that the Sol-Ark is my only option for a grid-tie inverter because of the price?  If that's the case, then it might not be the best option if I have to go up to 12K.

I called a vendor and it does seem like my options are pretty limited.  They don't carry Sol-Ark, but they did recommend some inverters from Schneider or the Outback Radian series or potentially the Outback Skybox.  We were only talking about inverters that support batteries, and I didn't get into the heat engine.  Nonetheless, the 8K Outback Radian is about $3K US less than the Sol-Ark 12K.  I hear they make good stuff.  Is there any reason that would not work?

Just spit-balling here:  does it make sense to get a separate inverter just for the engine and batteries?  This would allow me to go way smaller on the expensive inverter, and potentially save some money.  I'm seeing that two 4K inverters are sometimes significantly cheaper than one 8k, though obviously I'd have more work and miscellaneous expenses.

Thanks again for the replies.

Brian Church wrote:
some inverters from Schneider or the Outback Radian series or potentially the Outback Skybox.

These would all work, but yes they have to be battery based and grid-interactive.

I want to know what type of load the sol-ark 8kw was having problems with that a outback skybox or outback radian with 8kw of power would do better with.

Yes the Schneider, the radian, or the sol ark would be my choices.
I would want to know who had problems and with what kind of loads. In terms of pricing dont forget to add in the legally required breakers and disconnects you have to add on with the radian and Schneider built into the sol ark. Then add on the solar charge controller you have to add and the inverter controller all those items are seperate add ons from radian and schneider... the skybox is a different kind of unit also high frequency like the solark so if the 8k had problems starting loads the skybox would as well...

Pardon the delayed response.

S Bengi wrote:
I want to know what type of load the sol-ark 8kw was having problems with that a outback skybox or outback radian with 8kw of power would do better with.

I wish I'd asked that question, and now I can't recall which vendor I called.

David Baillie wrote:In terms of pricing dont forget to add in the legally required breakers and disconnects you have to add on with the radian and Schneider built into the sol ark. Then add on the solar charge controller you have to add and the inverter controller all those items are seperate add ons from radian and schneider... the skybox is a different kind of unit also high frequency like the solark so if the 8k had problems starting loads the skybox would as well...

If Sol-Ark's promotional material is to be believed -- and as you point out, there's at least some veracity to it -- then it may actually be the most affordable option.

With respect to problems with certain loads, I recall the rep said that Sol-Ark offers solutions to the problem, but they are not happy enough with them to recommend the 8k.  The price difference between the 8K and the 12K is not all that much, so it may make sense to go with the 12K just to be safe.  I'll dig a bit deeper into that.


Thanks for all the input guys.  I feel much better informed than going in.  I recognize I still have a lot to learn, but for now I'm on to researching batteries.  Thanks again!

You just need a battery/battery bank that can handle the max 1000W charge rate.
48V x 20Ah = 1000Wh (50x20)
Battery banks like a 25% charge rate aka 4x. So you need 4x1000W = 4000W
48V x 20Ah x 4 = 48V x 80Ah = 4000Wh

So a battery bank with 80AH is what you are looking for. But just 1000Wh will work esp given that the battery is not actually being charged or discharge, its just acting as a middle man.

Now if the grid goes down and your generator is still going and your battery is full, you will have to do something with that power aka a dump load.

Also if the grid goes down you will have very little power in your house if any, due to not having a sizable battery bank.
So how much power will you have, generator + battery aka P=G+B
P=1000W + (Battery x Discharge Rate)
P=1000W + (1000W x 5hr discharge rate)
P=1000W + (1000W x 0.2)
P=1000W + 200W (but technically you could pull it all out, in 1hr vs 5hrs)
With these numbers best case you can get 2kW but more like 0.6kW, now with a huge battery bank you could more.

Li-polymer battery with 12C x 48V x 20Ah = 12C x 1000w = discharge of 12,000W
LiFePO4 with 1C x 48V x 240Ah = 1C x 12,000Wh = 12,000W
Lead Acid = 0.2C x 48 x 1200Ah = 0.2C x 60,000Wh = 12,000W

S Bengi wrote:You just need a battery/battery bank that can handle the max 1000W charge rate.
48V x 20Ah = 1000Wh (50x20)
Battery banks like a 25% charge rate aka 4x. So you need 4x1000W = 4000W
48V x 20Ah x 4 = 48V x 80Ah = 4000Wh

So a battery bank with 80AH is what you are looking for. But just 1000Wh will work esp given that the battery is not actually being charged or discharge, its just acting as a middle man.

Now if the grid goes down and your generator is still going and your battery is full, you will have to do something with that power aka a dump load.

Also if the grid goes down you will have very little power in your house if any, due to not having a sizable battery bank.
So how much power will you have, generator + battery aka P=G+B
P=1000W + (Battery x Discharge Rate)
P=1000W + (1000W x 5hr discharge rate)
P=1000W + (1000W x 0.2)
P=1000W + 200W (but technically you could pull it all out, in 1hr vs 5hrs)
With these numbers best case you can get 2kW but more like 0.6kW, now with a huge battery bank you could more.

Li-polymer battery with 12C x 48V x 20Ah = 12C x 1000w = discharge of 12,000W
LiFePO4 with 1C x 48V x 240Ah = 1C x 12,000Wh = 12,000W
Lead Acid = 0.2C x 48 x 1200Ah = 0.2C x 60,000Wh = 12,000W

Thanks for the reply, and pardon the delay.

I saw some pretty good looking AliBaba sourced batteries reviewed on YouTube.

The specs list a max pulse discharge rate of 3C, so I presume they are 1C.

I was thinking of getting 1 kit of 4, 1P4S, so 48 V * 100 Ah = 4800 Wh

I didn't realize battery banks like a 25% charge rate, so it seems like my max input should be around 1200 W or 1.2 KW.

I could double that with 2P4S at some point down the road, which would allow me 9.6Kw hours of storage, which at a 25% charge rate would allow me an input of 2.4Kw.   I see that the MidNite Classic 150 supports up to 72V battery banks, so that would allow me to go up to 2P6S:

72 V * 200 Ah = 14400 Wh or 14.4 KWh

14.4 KWh * 1 C * 25% = 3.6 KW

Did I get that all right?

Thanks again!

It's $600 for 12v so you will need 4X for 48v. S0 $2,400.
You will then have to buy and setup a BMS. So the cost increases.
Then you have the consider the quality of the product that you just created and the fact that they are not CE UL certified.
Personally I would just drop in a single one of these $2,950 48V units. https://www.wholesalesolar.com/9580101/simpliphi/batteries/simpliphi-phi-3.8-kwh-48v-lfp-battery

Now if you can get some cheap/free used LiFePO4 cells, then I would go thru the hassle of making it over buying the 48v simpliphifi battrry.
Alternatively you could just use lead acid batteries. Sizing it so that it never goes above 80% charge(higher and charge efficiency plummets)

You have to match your battery bank to your inverter which is 48v. Now if both the charge controller, and inverter supports 72V, then yes you would have a go ahead.

Your 24KWH/day generator sub-system breakdown
$3,000 Generator
$1,000 Charge Controller
$3,000 Battery
Total = $7,000

This interface with your 16KWH/day solar system
$3,000 Solar Panel (4000watts)
$1,000 Charge Controller (estimated cost)
$6,000 Inverter  (the combined 12kW sol-ark inverter+charge converter is $7,000)
Total = $10,000

Backup (Grid Down)
$0 for the already accounted for Sol-Ark inverter
$0 extra for the 48v battery bank (for realistic backup you could 1 to 4 more $3,000 battery banks)
$0 extra for the two charge controllers
$0 extra for the night time and daytime energy source (1kw generator and 4kw day time only solar panel)

S Bengi wrote:It's $600 for 12v so you will need 4X for 48v. S0 $2,400.

You make good points beyond this (e.g. finding UL underwritten), but I got hung up on the first line because I totally thought they were each 12V.  That certainly changes the calculus.

I'll do more research on the DIY end, and compare it to your recommendation so I can generate an educated response.

To be honest, I am kinda attracted to DIY per se, but there's also something to be said for keeping it as simple and safe as possible.

Thanks again.



PS  I know I need a BMS, but I haven't done much research on that from a DIY perspective, so I didn't bring it up so as not to expand the scope of this thread anymore.

Excuse me, I know solar panels is safer, cheaper, and better for the environment.But I don't know how to heat greenhouse with solar panels? Can you give some advices? Thanks

Oh! I have found some information in here: https://www.avasolar.com/how-to-heat-a-greenhouse-with-solar-panels/ . I think someone maybe need it. It really useful for me.

Natalee/Moderators we should probably make this a separate thread.
Based on the link that you provided, after watching and listening the video. He only use a the solar panel to operate a fan to even out the greenhouse temperature that a wood stove was providing. The temperature at the top of the greenhouse was 90F but by the ground it was only 39F, basically the air temp was very stratified.

If you want to heat a greenhouse with solar energy,  you have to spend your money on insulating the the walls, leaving only the longer south/sun facing wall exposed (think solar heated passive house).

Here is the video that was embeded in the link that you posted previously.

As far as batteries- the most expensive and fragile part of a system- you might try industrial batteries. They are big heavy and expensive but last a lot longer. We’re running 4 Trojan Ind17-6’s now for almost 7 years and they’re still doing well. About to add a separate system with 4 Rolls 27-6’s. These were had for less than the Trojans bought years ago. It really pays to shop around for batteries!!! Saved hundreds if not a thousand $   Smart vendors will compete for your business if only you ask. If they’re put off, buy elsewhere. Ours we got from Solarbiz- they were very good and have been in solar business since Adam went off-grid.
Try shopping Craigslist ( Craig should get a Nobel prize)- I’ve seen great deals on entire systems. Happy hunting. Tom