Does This Setup Make Sense?

[cohunter14]

I purchased an off-grid cabin last summer that has a small solar setup on it. I am looking at expanding the cabin a bit and also adding a well, so I am trying to optimize the solar setup the best I can while using as much of what I currently have as possible to avoid extra expenses.

The current setup has six golf cart batteries, two different inverters (a Cobra CPI 880 (800w) and a Vector 2000 (2,000w)), two controllers (a Renogy Wanderer and a Sun Saver 10L), and two solar panels (a 100w and an 80w).

After doing a bunch of reading and watching videos, I am understanding solar more and more. The main issues I see with the current setup is, obviously, it's way under paneled, and the current controllers won't really allow for the appropriate number of panels. I have also read that it's difficult to charge six batteries evenly. Another thing I've realized is the 2,000-watt inverter uses a decent amount of power while it's on.

With all of that being said, here is what I'm considering doing: I'd like to separate the batteries into a set of two and a set of four and do two different solar setups. The first setup will utilize both of the current charge controllers, the 800-watt inverter, and the 100-watt panel. I would also add a 200-watt panel to this setup. This would then primarily power the lights in the cabin and a handful of outlets that will be used to charge phones, etc and I would plan on just leaving the inverter on the whole time I'm there since it doesn't use much for power. At most, I see this using 1,300 watts in a day.

For the larger setup with four batteries, I am thinking of using the 2,000-watt inverter along with this 600-watt kit from Rich Solar that Will recommends on his website: Rich Solar 600w Kit. This setup would power my well pump as well as the outlets in the kitchen, which would be used for high watt appliances like coffee makers, microwaves, the propane oven, and the occasional vacuum. I would anticipate this being used for 1,800ish watts a day, or just over 2,000 if I decided to leave the inverter on all day instead of turning it on only when needed.

I know theoretically I could use more panels than this, but this is in an area that's rated for 5.5 hours of optimal sun per day, so I'm only planning on really using enough panels to supply what I'll potentially use (and it's actually quite a bit more). We don't have much for winter access, so I'm not too concerned about that timeframe. If we do use it during that period, we won't be using the well either as we will winterize it.

I'd appreciate any input you have on this setup. Anything you would recommend or do different?

 

[sunshine_eggo]

After doing a bunch of reading and watching videos, I am understanding solar more and more. The main issues I see with the current setup is, obviously, it's way under paneled, and the current controllers won't really allow for the appropriate number of panels. I have also read that it's difficult to charge six batteries evenly. Another thing I've realized is the 2,000-watt inverter uses a decent amount of power while it's on.

Nice conclusions. You're a quick study.

Assuming 2S3P (12V) battery configuration, proper cabling and connection practices can ensure good charging on all 3 strings. It won't be perfect, but it will be acceptable.

With all of that being said, here is what I'm considering doing: I'd like to separate the batteries into a set of two and a set of four and do two different solar setups. The first setup will utilize both of the current charge controllers, the 800-watt inverter, and the 100-watt panel. I would also add a 200-watt panel to this setup. This would then primarily power the lights in the cabin and a handful of outlets that will be used to charge phones, etc and I would plan on just leaving the inverter on the whole time I'm there since it doesn't use much for power. At most, I see this using 1,300 watts in a day.

For the larger setup with four batteries, I am thinking of using the 2,000-watt inverter along with this 600-watt kit from Rich Solar that Will recommends on his website: Rich Solar 600w Kit. This setup would power my well pump as well as the outlets in the kitchen, which would be used for high watt appliances like coffee makers, microwaves, the propane oven, and the occasional vacuum. I would anticipate this being used for 1,800ish watts a day, or just over 2,000 if I decided to leave the inverter on all day instead of turning it on only when needed.

I would personally not choose this route. There is no advantage to simply just turning the 2kW inverter on and off as you need it. You are proposing to split your battery and solar into two separate systems. What happens when one is full, but the other needs charging? Now you have charging resources attached to the other system that are being unused, and a battery bank that can't be used for your immediate needs. You will also have two systems to manage. The idea of small and large inverter to address idle power is fine, but I wouldn't consider splitting them out without a very pressing reason.

Concerning a well pump, do your homework. Depending on the type of pump, well depth, etc., pumps can be a massive drain on a system. Pump motors often have a very large surge 5X the running current. Additionally, pump ratings are in OUTPUT. To get 3/4 hp out of a pump, you're going to have to put in 1.5-2X of electrical power.

I know theoretically I could use more panels than this, but this is in an area that's rated for 5.5 hours of optimal sun per day, so I'm only planning on really using enough panels to supply what I'll potentially use (and it's actually quite a bit more). We don't have much for winter access, so I'm not too concerned about that timeframe. If we do use it during that period, we won't be using the well either as we will winterize it.

"5.5 hours of optimal sun." Is this 5.5 solar hours (the equivalent "high noon" exposure with panel exposure from sunrise to sunset) or 5.5 hours of actual exposure? 5.5 solar hours is great. 5.5 total hours of solar exposure is terrible.

Sounds like you're off to a good start. You're planning, researching and asking questions before risking dollars.

 

[Wellbuilt]

for a cabin I like a 48volt system , 3600watt inverter / charger Quality charge controller
with 4000watts of solar I think this will be where you end up one day .?‍
That being said I would not split your system , keep your battery’s together .
i would use the 2000watts inverter get a quality mppt charge controller and fill it with panels 1200watts .
Your inverter most likely won’t start a well pump unless you have a soft start unit and your water is not deep .
Your microwave will run on low if your battery’s are @ full charge and I would make coffee in a pot on the stove .
I allso like to have at least 200watts of charging per golf cart battery .
As far as a well pump gos a 5500watt generator will power a smaller well pump , you can pump water into a tank and run a a/c or d/c RV pump to pressurize your system .

 

[MichaelK]

Frankly, I'd throw out all the low-end junk you have and just start over. The batteries I think are the only parts here worth keeping. I'd second WBs advice and go with a higher system voltage; that will require you to get two more golf-cart batteries. You can wire it either as 24V, 4S2P; or 48V, 8S1P.

Before starting though, complete an energy audit and actually determine what level of power you need. You mention the well pump. Is it 120V or 240V AC? Do you know how many amps it draws? Do you know the startup amperage draw? SE is very correct about well-pump power draw. For my 1hp pump, the startup surge is 8900W, and running wattage is 2200W. I answered those questions first before I started building my own system, which does run my well-pump.

At my own cabin on days when I do not pump water, I find myself using about 3000Wh per day of power. You may find it easier and cheaper to design a somewhat smaller system that can make that much power, but use a generator to power the pump. Or, you can dive in and build a system big enough to handle everything.

Let's say you buy the two extra batteries and wire them for 48V. Are they 250Ah batteries? To charge them properly you want to charge at 1/8th of C (250Ah?). 1/10 of C is still very good though. You should also factor in that panels almost never produce their rated power, so I always include a compensating fudge factor. I like to use 85% or 1.175X.

So, your math would be (250Ah/8) X 50V charging X 1.175FF = 1836W of panels. 1/10th C would be 1470W. Don't buy panels online. Buy locally, with local pickup. In my area right now I'm seeing 250W grid-tie panels for about 75$ each. Six or eight of those would cost you between 450 and 600$.

Next replace the PWM controllers with a good MPPT controller. Take a look at Epever's Tracer 5415AN controller. You could wire six panels in 3S2P. With a higher voltage controller like the Tracer 6420AN you could wire eight panels as 4S2P.

Get a sine-wave inverter to power the whole cabin. With sine-wave, you could power a refrigerator and any other motor-driven appliances. I'd look at Samlex, Magnum, Outback, Schneider, and Victron. Some models of each brand can be hard-wired directly into the cabin's main electrical panel. Don't shop for an inverter on Amazon.

 

[50ShadesOfDirt]

I'm assuming you have a 12v system? Is there some kind of charger? Cabin is expanding, and so will your power needs ...

1. add a generator ...

By adding a (propane) genny, you are covered no matter the scenario (low sun hours, high equipment loads and/or usage times, etc.) Can be a small 2000w inverter/generator, or a larger open-frame generator in the 5kw or thereabouts range (bigger is always better, unless you also want it to be portable for other needs). Propane is cleanest fuel, stores forever, and you can either do a larger service-fed tank, or smaller portable tanks. Any time the battery bank is low, top it off with a manual generator run. If solar is adding to the battery bank, no need to run the genny that day. If there is no charger, then you'll also need a charger matched to the battery voltage, and sized to replenish the battery bank. Generator also gives extra power for cabin expansion construction ...

2. Now tackle solar panels, to reduce generator runtimes. Don't know how old the old ones are, or what your possibilities are to get to 300w or larger panels, all of same brand. With the genny in place, no pressure to get the right amount of solar panels, just find the right deal along with necessary bits & bobs, and get that part done.

3. Take a hard look at the inverter(s) ... are they even pure sine wave output; are they possibly old technology? A bigger one is generally better, for various reasons discussed all over this site; newer is better (better programming, monitoring, etc.) Consider moving the two odd ones on, and apply the money to a larger 3kw with more features. Consider system voltage, inverter/chargers, and try to get to 24v or 48v ...

4. Finally, do the same with the batteries ... move these on, and try to get to a LiFePO4 battery bank, matching the inverter's voltage setting.

Unless very careful with one's power budget, loads and usage will almost always grow ... the above gives you headroom for the growth.

Hope this helps ...

 

[cohunter14]

Wow, lots of great information here. Let me respond to a bunch of this:

I would personally not choose this route. There is no advantage to simply just turning the 2kW inverter on and off as you need it. You are proposing to split your battery and solar into two separate systems. What happens when one is full, but the other needs charging? Now you have charging resources attached to the other system that are being unused, and a battery bank that can't be used for your immediate needs. You will also have two systems to manage. The idea of small and large inverter to address idle power is fine, but I wouldn't consider splitting them out without a very pressing reason.

What route would you go in my situation? The primary reason I am going this route is because of not being able to charge six batteries equally, and I've also read that I don't want to add new batteries to old, so I can't just make this an eight battery system without buying eight new batteries, when these six seem to be in solid working condition.

Concerning a well pump, do your homework. Depending on the type of pump, well depth, etc., pumps can be a massive drain on a system. Pump motors often have a very large surge 5X the running current. Additionally, pump ratings are in OUTPUT. To get 3/4 hp out of a pump, you're going to have to put in 1.5-2X of electrical power.

Great point. I have just made the assumption, again based on reading, that a well pump is going to be 1,000 watts. I'll have to speak to my well guy and see what pump he is planning on installing so I can get more information.

"5.5 hours of optimal sun." Is this 5.5 solar hours (the equivalent "high noon" exposure with panel exposure from sunrise to sunset) or 5.5 hours of actual exposure? 5.5 solar hours is great. 5.5 total hours of solar exposure is terrible.

Sorry, that is peak sun hours. This is in the mountains of Colorado, so plenty of sunshine.

for a cabin I like a 48volt system , 3600watt inverter / charger Quality charge controller
with 4000watts of solar I think this will be where you end up one day .?‍
That being said I would not split your system , keep your battery’s together .
i would use the 2000watts inverter get a quality mppt charge controller and fill it with panels 1200watts .

So, you would recommend just keeping it as a six battery setup? That would make things easier for sure. I've just heard that's a no-no.

Your microwave will run on low if your battery’s are @ full charge and I would make coffee in a pot on the stove .
I allso like to have at least 200watts of charging per golf cart battery .

That 2,000 watt inverter already does run a microwave and coffee maker in it's current setup, which is nice.

As far as a well pump gos a 5500watt generator will power a smaller well pump , you can pump water into a tank and run a a/c or d/c RV pump to pressurize your system .

That's something we have considered as well. In a perfect world, we would love to have the solar power the well pump on its own, so we don't have to fire up a generator that often.

 

[cohunter14]

Frankly, I'd throw out all the low-end junk you have and just start over. The batteries I think are the only parts here worth keeping. I'd second WBs advice and go with a higher system voltage; that will require you to get two more golf-cart batteries. You can wire it either as 24V, 4S2P; or 48V, 8S1P.

As I mentioned before, isn't adding new batteries to older batteries considered a bad idea?

Before starting though, complete an energy audit and actually determine what level of power you need. You mention the well pump. Is it 120V or 240V AC? Do you know how many amps it draws? Do you know the startup amperage draw? SE is very correct about well-pump power draw. For my 1hp pump, the startup surge is 8900W, and running wattage is 2200W. I answered those questions first before I started building my own system, which does run my well-pump.

At my own cabin on days when I do not pump water, I find myself using about 3000Wh per day of power. You may find it easier and cheaper to design a somewhat smaller system that can make that much power, but use a generator to power the pump. Or, you can dive in and build a system big enough to handle everything.

I do need to get more details on the well pump, like I mentioned above. Outside of the well pump and any power an inverter uses, I am projecting our solar usage to be just under 2,000Wh. This is a pretty small cabin though. It's currently just over 700 sq ft, and with the expansion it will probably be 1,100ish with a 300ish sq ft loft.

Let's say you buy the two extra batteries and wire them for 48V. Are they 250Ah batteries? To charge them properly you want to charge at 1/8th of C (250Ah?). 1/10 of C is still very good though. You should also factor in that panels almost never produce their rated power, so I always include a compensating fudge factor. I like to use 85% or 1.175X.

So, your math would be (250Ah/8) X 50V charging X 1.175FF = 1836W of panels. 1/10th C would be 1470W. Don't buy panels online. Buy locally, with local pickup. In my area right now I'm seeing 250W grid-tie panels for about 75$ each. Six or eight of those would cost you between 450 and 600$.

Next replace the PWM controllers with a good MPPT controller. Take a look at Epever's Tracer 5415AN controller. You could wire six panels in 3S2P. With a higher voltage controller like the Tracer 6420AN you could wire eight panels as 4S2P.

Get a sine-wave inverter to power the whole cabin. With sine-wave, you could power a refrigerator and any other motor-driven appliances. I'd look at Samlex, Magnum, Outback, Schneider, and Victron. Some models of each brand can be hard-wired directly into the cabin's main electrical panel. Don't shop for an inverter on Amazon.

I believe the batteries are 210Ah (they are the Costco Interstate Batteries brand).

That's crazy that you are finding panels that cheap. How do you find local companies selling panels at those prices?

I'm assuming you have a 12v system? Is there some kind of charger? Cabin is expanding, and so will your power needs ...

1. add a generator ...

Yes, 12v and there are charge controllers, but no other charger right now other than the small panels. And yes, the plan would also be to add a propane generator for backup.

3. Take a hard look at the inverter(s) ... are they even pure sine wave output; are they possibly old technology? A bigger one is generally better, for various reasons discussed all over this site; newer is better (better programming, monitoring, etc.) Consider moving the two odd ones on, and apply the money to a larger 3kw with more features. Consider system voltage, inverter/chargers, and try to get to 24v or 48v ...

4. Finally, do the same with the batteries ... move these on, and try to get to a LiFePO4 battery bank, matching the inverter's voltage setting.

The current inverters are not pure sine wave. The plan would be to use these for now, and eventually upgrade, especially the higher voltage one. But that one does run the current appliances without issue.

As far as the batteries go, I don't think lithium is a good idea based on what I've read. We won't be using the system that often, and it also has the potential to get pretty cold in the winter since it's in the mountains of Colorado.

 

[12VoltInstalls]

like to separate the batteries into a set of two and a set of four and do two different solar setups.

Assuming 2S3P (12V) battery configuration, proper cabling and connection practices can ensure good charging on all 3 strings. It won't be perfect, but it will be acceptable.

I agree. With a three-equal-length pos(+) and neg(-) cable setup joined to one single cable or busbar you will have balanced charge and balanced output to inverters and 12V loads. I differ only in that I think that’s more than acceptable

The 600W solar mppt kit is a good solution but maybe still a tad small for the battery bank? Wildhat guessing-wise.

If you won’t be too deep into the batteries it should be good. You can run the other two panels on one or two of the PWMs maybe facing South East or something for some earlier 160 or 180 nominal watts. You just want to still be 100% at sundown imho, and try to not dip below 75% charge overnights.

(a Cobra CPI 880 (800w) and a Vector 2000 (2,000w)

I’d want at least one of those to be pure sine wave not modified sine inverters. Mod sine is fine for coffemakers, hot plates, incandescent lights, heating elements, etc. but computers, tool chargers, microwaves, well pumps, fridges, some phone or most laptop chargers want a true sine wave. While they may work for a while on mod sine they probably either won’t or will fail in time - worse they could burn up immediately.

I could live with these components.
Sounds like you’re heading in a good direction.

Just for fun, instead of a kit try proving out some components and panels separately. You might be able to get more panels for the same cost. If it’s not doable time or convenience-wise the Rich kit saves the thinking a bit.

 

[12VoltInstalls]

As I mentioned before, isn't adding new batteries to older batteries considered a bad idea?

Yes. But if you fully charge and test the electrolyte and they’re good adding batteries isn’t going to nuke your system. It’s still not best practice but I’ve added lead acid batteries to things in the past and over the last few years to my own system without apparent consequences.
But there could be consequences in overall life of the new batteries, and apparent or not- a weak battery next to a good battery can make for charging/draining issues.

I view it like this: if you treat a lead acid battery well it most often lasts way longer than it should. So if you get 125% or 150% of general life expectancy (or more) and you “lose” 5% or 10% or whatever have you actually lost anything?! My current batteries are at oldest around 3? years old. Adding some on purpose last year and two years? back and more recently replacing two stolen ones…. It’s fine for me.
I’m certainly not recommending doing what I do- it’s not best practice and I know the issues. In fact I’d say it’s a bad idea. But no bunnies in Sri Lanka will die and you will not be arrested for assault and battery of a battery.

 

[Bellyman]

It sounds like your well pump is one of your biggest problems. I thought maybe I'd throw out a thought.

Could you put in some kind of storage tank that you could draw from with an RV water pump or similar to provide you pressurized water when you need it? If you could run a generator periodically to refill that storage tank, it would take the burden off of your main system to have to be able to deal with that large well pump at all.

Having lived in an RV for nearly a decade, having a 40 gallon (or so) fresh water tank onboard was quite livable. We had the typical 12v water pump but we added a pressure tank to smooth out the flow. It wasn't expensive or complicated. And I've been in houses that didn't have as nice of water pressure or flow. We just had to be careful of how much we used.

Some might depend on just how much water you're using. And if you would happen to be able to put a storage tank high enough above your intended point of use, gravity may be useful for providing pressure.

I can see the value in pumping hundreds (?) of gallons at a time rather than a half gallon here, another gallon in 3 minutes, another half gallon in 2 minutes, etc. All of those small uses use a lot of energy just in startups.

Perhaps of no help, but just thought I'd throw out the thoughts that came to mind. Good luck!

 

[TorC]

Since you'll be putting in a pump new, you have a much easier time of it than trying to power an existing well. There are the Grundfos SQFlex pumps that will take solar direct, battery, or even AC. There are soft starters that are pretty good for regular pumps, at least the 3-wire ones. You can also put in a 3-phase pump with VFD, that has nearly no start-up surge.

 

[Wellbuilt]

I use the SQF and pump from 700’ @ 6 gallons a min .
I was going to power it from solar panels but it seams like a wast of power .
I have 750’ of 10 g wire running into a 20 amp breaker with a timer switch
set for 30 mins the pump give me 180g and will use 350 watts every 3/4 days
this would be easy if the well was not so deep . The pump is $$$$$

 

[sunshine_eggo]

I use the SQF and pump from 700’ @ 6 gallons a min .
I was going to power it from solar panels but it seams like a wast of power .
I have 750’ of 10 g wire running into a 20 amp breaker with a timer switch
set for 30 mins the pump give me 180g and will use 350 watts every 3/4 days
this would be easy if the well was not so deep . The pump is $$$$$

Which model?

 

[Wellbuilt]

Which model?

I believe it’s a G SQF 6-3 rated for 820’
they have a lot of pumps with different pump curves I could of bought a pump SQF 3-3 that pumped 3Gallons
a min at 665’ and used half the power , I just did not run close to max out put .
My water gos from 150’ water level to 500’ some years .

 

[sunshine_eggo]

I believe it’s a G SQF 6-3 rated for 820’
they have a lot of pumps with different pump curves I could of bought a pump SQF 3-3 that pumped 3Gallons
a min at 665’ and used half the power , I just did not run close to max out put .
My water gos from 150’ water level to 500’ some years .

Thanks!