Newbie with a container needing advice

[TimmehTim]

Hello.
I modified a shipping container into a tiny home (maybe this should have been posted to Shipping Container Mods, but oh well) on some hunting land my family owns. We only went up for a couple nights a couple times a year so a generator worked well. We are now looking to spend more time up there and we're thinking about going solar. A friend had done some solar work on his property and had a few left over parts including 9 solar panels and a 5000w inverter. I'm trying to take advantage of what he gifted me and just need to figure out what other components are needed.

Panels *see photo: Jinko 315 watt × 9
(Should I run them all to a Combiner Box or run them in a series? Which is better?)
Combiner Box: ?? (I assume any will do provided it has enough connections and I'm not running my PV in series)
Charge Controller: ?? Please help me determine the correct specifications needed for this component.
Inverter: WZRELB 5000w 24v
Disconnect between combiner box and charge controller: ??
Disconnect between charge controller and batteries: ??
Battery meter: ?? I assume any will work?

And biggest question, BATTERIES. I want to be able to run 2000w for 8 hours.

I appreciate any kind words of advice and guidance.

 

[rmaddy]

Given the amount of solar (2835W) and the size of the inverter (5kW) you will probably want a 48V based system.

With 9 panels you could do 9P, 3S3P, or 9S. If you use just 8 of the panels you can do 8P, 2S4P, 4S2P, or 8S.

With 9 panels you have 2835W. On a 48V system that would mean up to 60A of charge current. With 8 panels you have up to 52.5A of charge current. A 50A SCC would be fine for that.

The solar panels have a Voc of 46.2V. 9S would be 415.9V. Depending on temperatures you would need an SCC that can accept 500V. That's probably too much. 8S would be 369.6V. An SCC that accepts 450V would probably work. That's doable. At 3S you are at 138.6V and you would probably need an SCC that accepts about 165V. And last, at 2S you are at 92.4V so an SCC that accepts about 120V should work. It all depends on the coldest temperature you will ever experience at the container.

If you end up choosing a layout that is 1P or 2P then you don't need a combiner box. Once you get to 3P or more then each string needs to be fused in a combiner box.

The battery will be need to be large. 2000W for 8 hours is 16000Wh. A 48V LiFePO₄ battery is really 51.2V so 16000Wh / 51.2V is about 313Ah. Assuming the 2000W is the load at the inverter, the inverter will actually pull more like 2350W from the battery. For 8 hours that's about 18,800Wh. So now you are looking at about 368Ah. So you need s 400Ah 48V LiFePO₄ battery. If you go with a lead based battery then you can only use 50% so you would need 800Ah 48V of AGM, Gel, FLA, whatever of battery.

That battery estimate assumes just one 8 period of 2000W continuous usage with no recharging (such as one cloudy day). Depending on your expected weather, you might need enough battery to last 2, 3, maybe 4 days without any recharging. Pick the number of days and multiply that times the previous estimate.

Is the solar enough? If you use 18800Wh of power in a day, your 2835W of solar would take 6.6 hours to recharge the battery. But that assumes you get 100% out of the panels for that entire time. That's not realistic. And you probably will be at a hunting trip when there's less solar in a day. So basically you need close to double the amount of solar panels to support an 8 hour 2000W load each day.

So really your first step is to reduce your loads a lot. 2000W for 8 hours a day is too much. What are those loads? Electric heat? Not a good choice. Go with propane or a diesel heater.

You should do a proper energy audit so you can see real numbers.

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

Figure out what you really need. Figure out how to reduce what you need. Then figure out what you really need to make it work.

 

[rmaddy]

Oops. I just realized you stated the 5000W inverter is 24V. So that doubles the amperage of the charge controller's charge current and it doubles the Ah capacity of the batteries you need (since they will be half the voltage).

24V is not nearly as good as 48V for such a large inverter and for the amount of solar you will need. The inverter may have been free but it may force you into a system that isn't the best solution for your needs.

 

[Bobert]

Please do an energy audit. it is often cheaper to replace inefficient items than to create enough storage and solar to power the inefficient devices. For instance an old ac unit might use 1000w and replacing it with a $1000 high efficiency mini split might get the same cooling for 500k that reduces the figure you mentioned by 1/4. It would take 7 agm 100 ah batteries to cover just that portion of the load . At $300 a pop that’s $2100 so upgrading ac in that hypothetical scenario would save you $1100 over feeding the status quo. Fridges
Are another common energy hog. A battery bank that would supply 16000 watts of power is about 26 100ah agm batteries. That’s almost $8000 in batteries that will need to be replaced in 5 years if you treat them right.
2000w an hour is doable but very expensive.

 

[TimmehTim]

Thank you gor all the info. Yes, the inverter is 24v. My 2000w for 8 hours is the absolute most I would draw. That's if I need to resort to running a space heater should propane or wood for the fireplace not be available for a day or two. The container is insulated so even though I say I'd run the space heater for 8 hours, the heater cycles on and off so it probably uses about half of that. I'm in the hills of Central Cali where we rarely have overcast days any longer. I'll still have my generator to use when the batteries get drained because of one or two cloudy days though.

 

[Bluedog225]

What a great analysis Rmaddy!

 

[time2roll]

16 kWh use overnight probably needs close to 20 kWh battery. About 24 280Ah cells for about $3,000 + BMS and supplies if building your own battery. A lot more if ready made 24 volters are purchased.

315w x9 x90% x5hrs is 12.7 kWh solar generated on a good day. Not going to replace all the power daily. Need to conserve or add solar. Probably better to get everyone an electric blanket than use a space heater.

Just my random thoughts. Best of luck.

 

[TimmehTim]

Given the amount of solar (2835W) and the size of the inverter (5kW) you will probably want a 48V based system.

With 9 panels you could do 9P, 3S3P, or 9S. If you use just 8 of the panels you can do 8P, 2S4P, 4S2P, or 8S.

With 9 panels you have 2835W. On a 48V system that would mean up to 60A of charge current. With 8 panels you have up to 52.5A of charge current. A 50A SCC would be fine for that.

The solar panels have a Voc of 46.2V. 9S would be 415.9V. Depending on temperatures you would need an SCC that can accept 500V. That's probably too much. 8S would be 369.6V. An SCC that accepts 450V would probably work. That's doable. At 3S you are at 138.6V and you would probably need an SCC that accepts about 165V. And last, at 2S you are at 92.4V so an SCC that accepts about 120V should work. It all depends on the coldest temperature you will ever experience at the container.

If you end up choosing a layout that is 1P or 2P then you don't need a combiner box. Once you get to 3P or more then each string needs to be fused in a combiner box.

The battery will be need to be large. 2000W for 8 hours is 16000Wh. A 48V LiFePO₄ battery is really 51.2V so 16000Wh / 51.2V is about 313Ah. Assuming the 2000W is the load at the inverter, the inverter will actually pull more like 2350W from the battery. For 8 hours that's about 18,800Wh. So now you are looking at about 368Ah. So you need s 400Ah 48V LiFePO₄ battery. If you go with a lead based battery then you can only use 50% so you would need 800Ah 48V of AGM, Gel, FLA, whatever of battery.

That battery estimate assumes just one 8 period of 2000W continuous usage with no recharging (such as one cloudy day). Depending on your expected weather, you might need enough battery to last 2, 3, maybe 4 days without any recharging. Pick the number of days and multiply that times the previous estimate.

Is the solar enough? If you use 18800Wh of power in a day, your 2835W of solar would take 6.6 hours to recharge the battery. But that assumes you get 100% out of the panels for that entire time. That's not realistic. And you probably will be at a hunting trip when there's less solar in a day. So basically you need close to double the amount of solar panels to support an 8 hour 2000W load each day.

So really your first step is to reduce your loads a lot. 2000W for 8 hours a day is too much. What are those loads? Electric heat? Not a good choice. Go with propane or a diesel heater.

You should do a proper energy audit so you can see real numbers.

System Energy Audit and Sizing Spread Sheet

To get the spreadsheet, click on the orange button at the top of this page. This sheet is intended to help you plan your system. Fill it out down to the last decimal place, look at the results..... and then make your best guess;) Notes...

diysolarforum.com

Figure out what you really need. Figure out how to reduce what you need. Then figure out what you really need to make it work.

The 2000w for 8 hours would be the heaviest usage and would be for times propane or wood for the stove wasn't available.

Understanding that this is a 24v system, and under the assumption I run 8 panels 2S4P. What would you recommend for SCC? I'm not good at this math at all. And with that, what should the specs be for my disconnects between the panels and SCC and the SCC and batteries and between the batteries and the inverter.

For the battery, sounds like I'd should get two 24v 200ah batteries and start. I'll get LiFePO so they last longer and I can add more to the system in time to have more storage.

Sound ok for a beginner to try?

 

[TimmehTim]

16 kWh use overnight probably needs close to 20 kWh battery. About 24 280Ah cells for about $3,000 + BMS and supplies if building your own battery. A lot more if ready made 24 volters are purchased.

315w x9 x90% x5hrs is 12.7 kWh solar generated on a good day. Not going to replace all the power daily. Need to conserve or add solar. Probably better to get everyone an electric blanket that use a space heater.

Just my random thoughts. Best of luck.

I'm looking at getting a used propane rv furnace and plumbing it in. Also thought about turning my tankless waterheater into a boiler and doing ambient floor heat. But until then it's the wood stove or propane space heater. Definitely going to have motivation soon.

 

[rmaddy]

2 24V 200Ah LiFePO₄ batteries is about 10.2kWh. They can handle a 2000W load for 5 hours. Do keep in mind that LiFePO₄ batteries can't be charged below freezing. LiFePO₄ may not be the best choice if this container will be left unused in the winter. Though you could always take the batteries with you when not being used in the container. There are some heated LiFePO₄ batteries so that could be an option if needed.

Your panels have a Voc of 46.2V. 8 in 2S4P would be 96.4V and 2520W. 2520W / 24V = 105A. One option would be a Victron 150/100. That can accept up to 150Voc and can output 100A of charge current.

You will need a combiner box with 4 fuses for the 4 strings of panels. The output will be about 4 x 9A = 36A. You need appropriate wire that can handle the 36A at 96V based on how long the wire will be from the panels to the charge controller.

With the panels properly fused at the combiner box, you can use a 2-pole breaker as a disconnect near the charge controller. But it must be rated for at least 125V and at least 50A. It needs the higher amperage since it's not there to protect anything, just act as a disconnect.

If you end up with a charge controller that outputs up to 100A of charge current then you need a 125A fuse between the charge controller and battery. This requires at least 4AWG (2AWG would be better) from the SCC to the batteries.

A 5000W 24V inverter can pull up to 5000W / 24V / 85% efficiency = 250A from the batteries. You may never use the 5000W but it's best to wire for it. That will require 4/0 wire between the batteries and inverter. You should have a 300A Class T fuse close to the batteries.

 

[time2roll]

I keep thinking to go 3s3p on the solar panels to use them all. Need a 200v controller as 3s is too much for 150v.
Maybe this EPEVER: https://www.amazon.com/EPEVER-Controller-Negative-Battery-10420AN/dp/B07KB6FMCX?th=1

Would be slightly over paneled and might clip power but generally not going to be at 100% production very much anyway.

 

[TimmehTim]

I keep thinking to go 3s3p on the solar panels to use them all. Need a 200v controller as 3s is too much for 150v.
Maybe this EPEVER: https://www.amazon.com/EPEVER-Controller-Negative-Battery-10420AN/dp/B07KB6FMCX?th=1

Would be slightly over paneled and might clip power but generally not going to be at 100% production very much anyway.

What if I got a 10th panel and wired them in 2 series of 5 panels and used two PowMr 60amp 160vdc MPPT SCC (or similar)?

 

[TimmehTim]

2 24V 200Ah LiFePO₄ batteries is about 10.2kWh. They can handle a 2000W load for 5 hours. Due keep in mind that LiFePO₄ batteries can't be charged below freezing. LiFePO₄ may not be the best choice if this container will be left unused in the winter. Though you could always take the batteries with you when not being used in the container. There are some heated LiFePO₄ batteries so that could be an option if needed.

Your panels have a Voc of 46.2V. 8 in 2S4P would be 96.4V and 2520W. 2520W / 24V = 105A. One option would be a Victron 150/100. That can accept up to 150Voc and can output 100A of charge current.

You will need a combiner box with 4 fuses for the 4 strings of panels. The output will be about 4 x 9A = 36A. You need appropriate wire that can handle the 36A at 96V based on how long the wire will be from the panels to the charge controller.

With the panels properly fused at the combiner box, you can use a 2-pole breaker as a disconnect near the charge controller. But it must be rated for at least 125V and at least 50A. It needs the higher amperage since it's not there to protect anything, just act as a disconnect.

If you end up with a charge controller that outputs up to 100A of charge current then you need a 125A fuse between the charge controller and battery. This requires at least 4AWG (2AWG would be better) from the SCC to the batteries.

A 5000W 24V inverter can pull up to 5000W / 24V / 85% efficiency = 250A from the batteries. You may never use the 5000W but it's best to wire for it. That will require 4/0 wire between the batteries and inverter. You should have a 300A Class T fuse close to the batteries.

Ok. Maybe sealed lead acid because it does freeze at nights. What if I did four Mighty Max 12v 200ah sealed batteries in 2 series of 2 batteries? That would give me 24v 400ah, correct?

 

[Bobert]

Ok. Maybe sealed lead acid because it does freeze at nights. What if I did four Mighty Max 12v 200ah sealed batteries in 2 series of 2 batteries? That would give me 24v 400ah, correct?

It is very difficult to keep a lead acid battery bank properly charged in winter months depending on how far north you are. Lead acid will still work below freezing but performance charging and discharging drops exponentially as the temperature drops. I can elaborate later if you would like I. Went from an fla battery to lithium mid fall.

 

[time2roll]

What if I got a 10th panel and wired them in 2 series of 5 panels and used two PowMr 60amp 160vdc MPPT SCC (or similar)?

That is fine too. OK to stick with 8 panels and see how it goes for now.

 

[TimmehTim]

How do I calculate the my solar arrays outputs when wired in series?
These panels are 37.2v and 8.48amps, if I'm reading it correctly. So if I wire 5 in series, it'll become 186v and 8.48amps. Is my math right?

 

[rmaddy]

How do I calculate the my solar arrays outputs when wired in series?
These panels are 37.2v and 8.48amps, if I'm reading it correctly. So if I wire 5 in series, it'll become 186v and 8.48amps. Is my math right?

Correct. Things in series you add voltage. Things in parallel you add amperage.

But, importantly, it is Voc, not Vmp, that is needed when comparing the voltage against the max PV input voltage of an SCC.

 

[TimmehTim]

Correct. Things in series you add voltage. Things in parallel you add amperage.

But, importantly, it is Voc, not Vmp, that is needed when comparing the voltage against the max PV input voltage of an SCC.

Ok. So the Voc for these panels is actually 46.2v, so 5 in series would give me 231v... so if I got a 200v SCC it would be slightly over paneled by 31v. Am I following this right still?

Should I use Isc or Imp to calculate amps? Assuming I should use Imp, which is 8.48amps, wiring 2 sets in parallel would give me 16.96amps.

So wiring two 5 panel series together in parallel I'd get 231v and 16.96amps

If I took 5 panels and wired them in parallel I'd get 46.2v and 42.4amps. If I wired 2 of those arrays together in series I'd then get 92.4v and 42.4amps

Is that all right?

With all the above in mind, if I'm following it all correctly, that means that if I used
- option 1 (two parallel sets of 5 panels in series) I'd charge my batteries faster but I'd only have 16amps of service (during sunny hours) and I'd be producing more power than my system can actually bring in.
- option 2 (two series sets of 5 panels in parallel) I'd charge my batteries a bit slower but have access to 42amps of service (during sunny hours).

How did I do?

 

[rmaddy]

Ok. So the Voc for these panels is actually 46.2v, so 5 in series would give me 231v... so if I got a 200v SCC it would be slightly over paneled by 31v. Am I following this right still?

You must never exceed the SCC's max PV input voltage. And a panel's Voc goes up as it gets colder. You absolutely can't put 5 of those panels in series on a 200V SCC. Not even a 250V SCC would work unless you never ever see temperatures below freezing.

Overpaneling is not related to the panel voltage or the SCC's max input voltage. It's about the total wattage and what is normally supported by the SCC and the resulting possible charge current.

Should I use Isc or Imp to calculate amps? Assuming I should use Imp, which is 8.48amps, wiring 2 sets in parallel would give me 16.96amps.

The two values are always close. Just assume the larger one to calculate wire sizes.

So wiring two 5 panel series together in parallel I'd get 231v and 16.96amps

Yes.

If I took 5 panels and wired them in parallel I'd get 46.2v and 42.4amps. If I wired 2 of those arrays together in series I'd then get 92.4v and 42.4amps

Yes but you wouldn't do that. You are suggesting 5P2S. You should instead do 2S5P. Take two panels and put them in series. Repeat that 4 more times. You now have 5 pairs of panels with each pair in series. Now connect those 5 pairs in parallel.

Note that when you have 3 or more parallel strings (5 in this case) then you must use a combiner box and fuse each string.

- option 1 (two parallel sets of 5 panels in series) I'd charge my batteries faster but I'd only have 16amps of service (during sunny hours) and I'd be producing more power than my system can actually bring in.
- option 2 (two series sets of 5 panels in parallel) I'd charge my batteries a bit slower but have access to 42amps of service (during sunny hours).

The charging speed wouldn't change. Both ways are 10 panels and the same total wattage. The SCC will have the same amount of incoming power so it will put out the same charge voltage and current either way. This assumes no shading resulting in different input power.

 

[TimmehTim]

That is fine too. OK to stick with 8 panels and see how it goes for now.

If I used 2 SCCs, do they both have to have the same outputs to work? Can I wire one SCC with a 4 panel series and the second SCC with a 6 panel parallel? And then combine those SCCs at the battery bank. If one array was providing its SCC with 184.8v and 8.48amps, and the second array was providing its SCC with 46.2v and 50.88amps will it work?