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Brian Ray
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# Posted: 31 Aug 2020 02:23pm
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I have four - 100 watt moncrystalline panels wired in parallel for 12 volts. These are installed in an area that receives mixed sun/shade throughout the day. I would like to wire these in series for 48 volts, but I'm concerned they may not function as well at 48 volts due to the partial shade.
My thought is, wired for 12 volts, one panel will produce current in direct sunlight even if the other three are in shade. Wired in series for 48 volts, do all four panels need direct sunlight? Or will I still get 48 volts if some of the panels are in shade?
Unfortunately, the alternating sun/shade throughout the day is unavoidable in my area.
Thanks for your time.
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Brettny
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# Posted: 1 Sep 2020 07:13am
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Do some tests. You could also wire 2 in series and 2 in parallel.
my real world tests showed that wireing in series is better in shade. This keeps the voltage up. Wireing all in parallel means that when there all shades its prob not going to charge any. The charge controller cant output voltage below battery voltage so 12v pannels on a 12v system can be really limiting.
I did real world tests useinf two 235w pannels wired in series. I covered one with a piece of cardboard and the charging amps went down to nearly nothing. But in actual real world use two pannels next to one another would have about the same sun exposure. Having my pannels out in a shady area confirmed this.
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Brian Ray
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# Posted: 1 Sep 2020 11:01am - Edited by: Brian Ray
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Thanks for the input Brettny.
The reason I'm researching this is because I would like to move the panels to an area that gets the most sun. This location is further from the cabin and I would like to avoid the large cable that would be needed at 12 volts.
I now have six – 6 volt deep cycles so I would need to invest in a new battery bank to go 48V, a bit of an investment so I want to get it right the first time.
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ICC
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# Posted: 1 Sep 2020 11:19am - Edited by: ICC
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Quoting: Brian Ray I now have six – 6 volt deep cycles so I would need to invest in a new battery bank to go 48V....
No.
The battery bank should be a lower voltage than what the panels are rated at.
The charge controller must be able to accommodate whatever the incoming voltage is AND it must be designed for use with the voltage of the battery bank. Many CC can handle a 12, 24 or 48 volt battery. This assumes you have an MPPT charge controller. Those can efficiently use the higher input voltages on a lower voltage battery bank.
I have up to 440VDC going into the CC for a 48 volt battery bank.
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Brettny
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# Posted: 1 Sep 2020 11:34am
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Wireing in series to get to your CC means you also have less line loss. Wireing pannels to 48v with a 12v system just means you would need a MPPT charge controller. Get a decent one. The cheap ebay ones sold by many dif sellers are not efficient at all. My pannels can output 62v in series and my CC converts that down to 12v with higher amps.
Maybe you should tell us about your system more.
If your sun is far away from the point of use some times it's better just to make the long run 120v AC. Ac travels better but this would mean having all your equipment near the sunny area.
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Brian Ray
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# Posted: 1 Sep 2020 02:16pm
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Quoting: ICC No. The battery bank should be a lower voltage than what the panels are rated at.
I would need to upgrade my battery bank to run a 48 volt system.
These 12 volt panels have an operating voltage of about 18 volts, so would exceed the 50+ volts of a 48V system.
I have a Morningstar controller. It's not MPPT, but has been very reliable.
My concern is the efficiency of 4 - 12V panels wired in series with half the panels in shade.
Response from the panel manufacturer: "When you connect your panels into a series connection, the tendency will be if one panel is shaded, it will be a domino effect for all your panels. We highly suggest that as much as possible, you connect your panels using a parallel connection"
Quoting: Brettny Maybe you should tell us about your system more.
Four - 12V – 100 watt panels wired in parallel to a Morningstar Tristar TS-45 controller. The controller is charging six – 6V deep cycle batteries wired in series/parallel for 12 volts.
The system is about 5 years old and has been very reliable, but when November comes, I find myself running a generator to supplement the low output from the panels. I have an area on my property that gets a little more sun than the panels current location, but is about 30 feet from the battery bank. I could relocate the entire system to the solar panel location and run 120V AC to the cabin, but I would like to store the batteries in the cabin to keep them warm while I'm there.
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ICC
Member
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# Posted: 1 Sep 2020 02:38pm - Edited by: ICC
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Quoting: Brian Ray These 12 volt panels have an operating voltage of about 18 volts, so would exceed the 50+ volts of a 48V system.
Yes, the panel would have a Vmp of about 17 to 18 volts or so. A 12 volt battery, when being charged via most charge controllers will be at a voltage of 14.4 volts. The charge voltage must be higher than the nominal battery voltage in order to push the current in.
A 48 volt battery would be charged at about 14.4 x 4 = 57.6 volts.
The TS45 can handle input of up to 125 volts. It could be used to charge the 12 volt bank but it would be very wasteful of the series connected voltage.
Thirty feet is still well within the range of connecting panels. Depending on your wire they might be okay and just need splicing extra lengths. That could be calculated when all the panel details and wire sizes are known.
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ICC
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# Posted: 1 Sep 2020 02:50pm - Edited by: ICC
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While shade on one panel of a series connected string will reduce the string output thete can also be problems in parallel arrays. On cloudy days the voltage may be so low as to be insufficient to get s charge pushed into the battery. If it is a hot but cloudy day it gets worse as panel voltage drops as the panels get hotter. That is one reason I don't like roof mounted panels.
Brettny was pointing out that series can be beneficial when sunshine is sub-optimal. While the output of a shaded or cloud obscured panel in parallel may be too low, a MPPT controller with panels in series, feeding a lower voltage battery, would very likely be able to still charge the battery bank.
Does that make sense?
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Brettny
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# Posted: 1 Sep 2020 03:14pm
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Thank you ICC. That is what I'm saying.
Change your PWM Charge controller for a MPPT gives you the ability to use all the other equipment you own now and wire the pannels in series. I believe its also the cheapest option. EP ever charge controllers that are 40a are under $150.
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scott100
Member
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# Posted: 8 Sep 2020 02:44pm - Edited by: scott100
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Ok, I'll be the oddball here, but wiring it all in series can kill the output of the system if only 1 of those panels is partially shaded. Since all the cells are in series on the shaded panel, its current is limited severely by the shaded cells. If all is wired in series, that panel will limit the other 3 to its current.
If you wire the 4 panels in parallel for a 12 v system, you at least get a chance to get something out of the other panels. True, the voltage will be limited by the shaded panel, but in most cases you will at least have enough for some charging current.
Here's a good link for an explanation of shade effect:
https://www.google.com/url?sa=t&source=web&rct=j&url=https://blog.aurorasolar.com/sha ding-losses-for-pv-systems-and-techniques-to-mitigate-them/%3Fhs_amp%3Dtrue&ved=2ahUK Ewitv-jXldrrAhXJt1kKHeeQCXAQFjACegQIARAB&usg=AOvVaw0-Qtho4ZJah8vy6DAVxbc4&cf=1
Other possibilities....use 2 controllers. I did this on our boat where half of the solar array can get more sun than the other half. The 2 victron controllers are networked to work together for optimum efficiency.
Ideally, get the panels out in the sun. At our cabin I mounted ours on the roof of our "solar shed". It's in a field 200' from the cabin. Controller, battery bank, and inverter is inside the shed and 120v ac is run to the cabin from there.
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Steve_S
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# Posted: 9 Sep 2020 09:51am
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I quickly ran through this thread and have a couple of thoughts in general.
If you want a 24V or 48V battery system, you will need sufficient voltage & amperage off the panels to support that Battery Voltage. You will also need enough panel to be able to charge your battery bank during the "Lowest Sun Hour Days" (December/January in North America).
Your Battery Bank, once you have it sized up to support your load requirements and reserve storage, you can then determine the amount of Panel required to support the batteries.
The Solar Controller should then be sized to support the amount of panels required for the battery bank it has to charge. SCC's (Solar Charge Controllers) can support up to 250V solar Input and some even higher. Some SCC's can be placed in series to handle separate array's while charging a single battery bank. (some interact, others do not).
In the US, you also have easy access to companies like https://www.santansolar.com/ who have incredible deals on New, New Old Stock & Used Certified panels. Pretty damned near impossible to get a better deal anywhere.
UNFORTUNATELY. There is no indication here why you are considering 48V and given what your starting out with I have to question this. How many Watts do yu think your cabin will pull ? What is the target power genetaion that you need ? kWh per day usage, Highest Peak Loads and so on.
12V supports up to 2000W which is 166A @12V *
24V supports up to 4000W which is 166A @ 24V *
48V supports up to 8000W which is 166A @ 48V *
* = uncorrected for inefficiecies. This is basic and also excluding surge potential which for Low Frequency Inverters, that is typically 3X. Systems can exceed these sizes with upgraded writing etc.
Lastly, appreciate that LFP, LiFePo4 batteries have dropped seriously in pricing, to the point where using FLA batteries now is nearing ridiculoussness.
LFP Prismatic Packs are the easiest to build & setup, here'sa quick tidbit example.
12V requires 4 Cells, 24V = 8 cells, 48V = 16 Cells in simple series to make one complete battery pack.
280AH cell Example. (Most popular currently)
Cell Cost Delivered DPP to USA duty/taxes included.
4 Pcs 3.2V 280Ah = US $457.60 {3,360wh min}
8 Pcs 3.2V 280Ah = US $891.44 {6,720wh min}
16Pcs 3.2V 280Ah = US $1,621.38 {13,440wh min}
REF: Shenzhen Luyuan Technology Co., Ltd. These are NEW, Grade-A class cells.
Regarding Solar Controllers, Inverters and such. As you are aware, there are a myriad of ways to skin that Herd of Cats. Over the past 5 years Huge Strides have occured in the industry and rings are changing very fast and increasingly so. Solar Power is mainstream now.
There is component builds with separate pieces, there are Unified Famiy products that work together (Vistron for example) and there are "AIO'S" or All In Ones which solve a heap of issues.
Gowatt is a Huge Tier-1 company makes excellent tech. MPP-Solar is a 2nd tier company, offerring similar products like GroWatt at a lower price point. They may be worth your while to have a look at.
REF:
GroWatt USA
MPP SOLAR USA
BTW, I use component system, with Midnite Solar C-200 & Samlex EVO Inverter/Charger, running with 956AH of Lead & 910AH of LFP, will be pure LFP Only by end of this month.
Bottom line, figure out what your intended usage in watts & watt hours will be, add 20% for the unexpected. then you can size battery bank to support that load / need at which point you will know how to size the solar controller & panels to support it.
Have a Plan because without a Plan you risk financial "ouch" and failure. Take you time, don't rush, NO Impulse Buying (there are always deals), no such thing as a "once in a lifetime gotta get it now or you'll loose out" stuff. If you see something like that RUN !!!
Hope it Helps, Good Luck
Steve
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Brian Ray
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# Posted: 9 Sep 2020 02:51pm
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Quoting: scott100 If you wire the 4 panels in parallel for a 12 v system, you at least get a chance to get something out of the other panels.
Thank you Scott100, you've answered my question and confirmed the information from the panel manufacturer.
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Brian Ray
Member
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# Posted: 9 Sep 2020 03:13pm - Edited by: Brian Ray
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Quoting: Steve_S I quickly ran through this thread and have a couple of thoughts in general.
Thanks Steve_S,
The property south of mine is full of old growth big leaf maples.
The 12V system I have in place is ok, I was just thinking about increasing performance by moving the panels to an area with more sun exposure. Due to the distance, I would need to increase the wire size to 2 gauge.
I was thinking about a 48 volt system to get away with a smaller conductor, but I will still be getting spots of shade throughout the day, so I'll keep it as is at 12 volts.
I appreciate all the responses.
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Steve_S
Member
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# Posted: 9 Sep 2020 03:35pm
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I wonder how you are figuring that. With panels in Series, the line voltage increases, in parallel the amperage is increased. My panels for example 4 in Sewries, 2 parallel strings, produces just under 200VDC which runs 45' underground to my powerhouse & SCC , Batteries & Inverter/Charger. That in turn runs AC underground 75' to the "Shack".
The combinner at the panels brings it all together and delivers the DC power to powerhouse via 10/2 with very minimal loss.
Good Luck, Have Fun, it's all an adveture.
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Brian Ray
Member
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# Posted: 9 Sep 2020 04:30pm
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4 panels in parallel are capable of about 20 amps, to run 100' to the controller and battery bank would require 2 AWG cable to avoid a significant voltage drop. The batteries need to stay in the cabin.
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Brettny
Member
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# Posted: 9 Sep 2020 06:45pm
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100' run of 12v is asking alot. Raise the voltage, series connect them and get more pannels.
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scott100
Member
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# Posted: 10 Sep 2020 12:18am
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Or
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scott100
Member
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# Posted: 10 Sep 2020 07:34pm
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Here's the rest of what I tried to write above. For whatever reason, my phone wasn't playing with the web site last night well. Couldn't edit above or post another message. Got the "forbidden" error, like I wasn't logged in, even though I was.
Or just put the inverter at the location of the solar panels and run 120 vac from there to cabin (provided you are planning to run the cabin on ac and not dc).
I did this on ours as I had a 200' run and it was cheaper and more efficient to run the ac that distance than to buy big copper dc cables to do it.
At the solar panel end (6 x 160 watt panels), I did a 24v series / parallel run so I could get by with 10 ga wire and use mc4 connectors.
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