Black Pearl
New Member
- Joined
- Jun 12, 2022
- Messages
- 34
Within the limits of your wire and/or connections that is...
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Beginner w/8 100W 12v panels in series to chg 2 LiPo4 12v batts: 60Amp MMPT or PWM for shade?
- Thread starter El Tigre
- Start date
Great to know.
I modified my sketches to use Voc for voltage (I know it doesn't really create 480.4W but, with our margin of error included by using the higher Voc it looks bigger...below it I also showed the calculations that come to the correct normative 400W). But I will, as suggested use the higher Voc voltage values in calculating how much voltage from a set of cells can be handled by a given SCC....
...also, just wondering,
1. In the sketches above (in addition to using VoC for the voltage in considering SCC limitations) should I also be using the higher current value (the short circuit current Isc of 6.5) for the amps when considering the limitations of some SCC? Or should I continue to use the Optimum Operating Current (Imp) which is 5.56A as I did in the above?
2. is the reason fuses aren't required because, in your example just above, the Voc (even when multiplied by 4 in series) is less that the 150v? What is the rule margin for that? (At what magnitude of margin do you say "hey, who needs a fuse?" (or is there some other criteria for deciding whether or not to use fuses?
Thanks!
Rednecktek
Solar Wizard
Since you're nowhere near the maximum input level I wouldn't worry about it. Something that took me a while to wrap my head around is that solar panels don't PUSH power into a system, the system ASKS for power and the panels provide what is asked. If your system is shut down and only drawing 50w, the panels are only going to produce 50w. If the system is asking for 500w they're going to try to produce 500w and just not make it. In your case the 6.5a is what could be produced if you just dead shorted the wires of the panel together which is a "bad thing" and the 5.5a Imp is what the panel can shove through the wires if it really has to. Since you're not trying to shove massive amounts of current through there, there's no worries. When calculating for "How much Should I get out of these panels" use the 5.5a Imp numbers.
Nope, the reason fuses aren't needed is because you only have 2 strings. An oversimplification might be that if you have a pair of 200w strings and one of those strings has a short, the other string balances it out and you just lose performance. If you had 3 sets of 200w strings and one string shorted, then that would be 2x the power from the good strings trying to go through the path of least resistance and into the bad string. Now you want a fuse to pop instead of your string. Basically, you don't need fuses unless you have 3 or more strings.
Other than that it looks like your sketch is spot on.
1. So, when I do later expand to an 800W-900W system, I might choose to use 4S2P instead of 3S3P (despite the ~100W potentiall difference in yield) just to avoid needing fuses? (Just making sure I understand the "rule of fuses"Since you're nowhere near the maximum input level I wouldn't worry about it. Something that took me a while to wrap my head around is that solar panels don't PUSH power into a system, the system ASKS for power and the panels provide what is asked. If your system is shut down and only drawing 50w, the panels are only going to produce 50w. If the system is asking for 500w they're going to try to produce 500w and just not make it. In your case the 6.5a is what could be produced if you just dead shorted the wires of the panel together which is a "bad thing" and the 5.5a Imp is what the panel can shove through the wires if it really has to. Since you're not trying to shove massive amounts of current through there, there's no worries. When calculating for "How much Should I get out of these panels" use the 5.5a Imp numbers.
Nope, the reason fuses aren't needed is because you only have 2 strings. An oversimplification might be that if you have a pair of 200w strings and one of those strings has a short, the other string balances it out and you just lose performance. If you had 3 sets of 200w strings and one string shorted, then that would be 2x the power from the good strings trying to go through the path of least resistance and into the bad string. Now you want a fuse to pop instead of your string. Basically, you don't need fuses unless you have 3 or more strings.
Other than that it looks like your sketch is spot on.
)2. Do the fuses provide any additional protection that might make me want them anyway? These here...
https://www.amazon.com/Leehitech-Co...65960&sprefix=mc4+inline+,aps,242&sr=8-4&th=1
claim solar surge protection, etc.?
Thanks!
(Please see the post just above too.)
I love the price!!! Wondering about how well it works with LiFePo4 batteries (and maybe noise). What do you think (here's a review at the Amazon link you sent:
If your application uses anything except lithium ion batteries I think this product is very acceptable, not great but very acceptable.
The problem with lithium ion batteries is when they are fully charged they disconnect. The output of this charge controller will then jump above set the set output voltage causing any load to possibly malfunction or be damaged.
What I originally liked about the product is that it has a high transfer efficiency and is able to support up to 60 A into a 48 V battery bank. It is fan cooled when the output current starts rising significantly but the fan is not at all noisy.
The user interface is rather primitive and there is no Bluetooth or remote monitoring function available so what you see on the screen is what you get it takes a little while to get used to how to program it and the program options are fairly limited.
Thoughts?
Thanks!
I am using my MSB with my LiFePO4 battery bank. You do have to set the unit to lithium battery and in my case I dropped the charge voltage less than my AIO on the Main array is set to. This allows the second array to act as a float when the main array is curtailed after reaching full charge status. The fan on the MSB only comes on when the unit goes above 45C and than back off at 40C.
Regarding the review. it sounds like the reviewer did not understand how to set the SCC. Lithium batteries would only disconnect (BMS) if they were overcharged or a cell imbalance has happened. The comment about not having Bluetooth or remote monitoring is correct. Though there is a WiFi model available. In my opinion I do not care for things like remote monitoring or Bluetooth. I also do not use BMS communication. I like things simple.
My thinking on the MSB is it is a basic SCC of better quality than the real simple dead cheap ones that lack a screen for readout and are questionable about if they are MPPT and actual capacity.
ETA: I am not saying for your needs the MSB SCC is the best choice. Indeed you might be best off with the Victron SCC or a Midnight Solar.
Regarding the review. it sounds like the reviewer did not understand how to set the SCC. Lithium batteries would only disconnect (BMS) if they were overcharged or a cell imbalance has happened. The comment about not having Bluetooth or remote monitoring is correct. Though there is a WiFi model available. In my opinion I do not care for things like remote monitoring or Bluetooth. I also do not use BMS communication. I like things simple.
My thinking on the MSB is it is a basic SCC of better quality than the real simple dead cheap ones that lack a screen for readout and are questionable about if they are MPPT and actual capacity.
ETA: I am not saying for your needs the MSB SCC is the best choice. Indeed you might be best off with the Victron SCC or a Midnight Solar.
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Thank you ALL for your help!!! I'm sure there's more to buy but here's (sketch below) of all I know that I'm buying (unless somebody responds with "well hold on just a minute partner...")
1. I heard here that I didn't need fuses with 4S2P so none are shown in the sketch below.
2. The 24" cables seem able to connect to each other as is. Of course I'll need cables to get to the SCC which I'd like to have inside the house.
3. Have to attach to the roof w/something. How about:https://www.amazon.com/HQST-Solar-P...12f-8610-7837ce06dc22&pd_rd_i=B06Y5QX9VX&th=1
4. Does this 4S2P connected system look like it would work well? Thanks again!!
1. I heard here that I didn't need fuses with 4S2P so none are shown in the sketch below.
2. The 24" cables seem able to connect to each other as is. Of course I'll need cables to get to the SCC which I'd like to have inside the house.
3. Have to attach to the roof w/something. How about:https://www.amazon.com/HQST-Solar-P...12f-8610-7837ce06dc22&pd_rd_i=B06Y5QX9VX&th=1
4. Does this 4S2P connected system look like it would work well? Thanks again!!
Rednecktek
Solar Wizard
Looks good!
Black Pearl
New Member
- Joined
- Jun 12, 2022
- Messages
- 34
Looks good. You gotta get your hands dirty and start learning hands on somewhere.
IDK if this link will be helpful, but it was helpful to me several years ago. I didn't incorporate my first system into a vehicle, nor did i purchase everything on the list, but as a newbie to something bigger than a solar powered gate opener back then, it was helpful.
Good luck!
IDK if this link will be helpful, but it was helpful to me several years ago. I didn't incorporate my first system into a vehicle, nor did i purchase everything on the list, but as a newbie to something bigger than a solar powered gate opener back then, it was helpful.
Good luck!
Large RV Solar Power Blueprints
Building a vehicle mounted solar power system? Let me help.
www.mobile-solarpower.com
Should get you going.
Depending on your shading you might find trying a 2S4P setup to be more productive. Since you are running 12vDC batteries you can get by with the ~45Voc if wired that way. If you do go that direction I would suggest getting a combiner box.
OH... also use 10awg solar wire even if you could get by with 12awg on the proposed first setup. It will allow your more latitude for changing things about in the future.
Yes, I guess 2S4P would be better (I'd read that parallel was better for shady environments because if one panel gets shade it doesn't limit the overall harvest as much). I wonder then, would 1S8P (all 8 panels in parallel) be even better (if 4 get shade the other 4 get full current and the shady 4 still kick in a little since current is summed in parallel). But would an all parallel network make use of the MMPT SCC?? If I regularly got half in shade for part of the day would it be better or no better than PWM ?
Problem with all 8 in parallel is your amps go to ~45a which is beyond MC4 connector ratings plus you would need heavier gauge wiring. With 2S4P you are ~22a which is less than the 30a rating and within reasonable run length for 10awg.
Rednecktek
Solar Wizard
Just stick with 2 strings, keep it simple.
Pi Curio
Sunlicious
With DC, the only difference is in the flexibility of the cable, that is, a multi-strand cable is more flexible and easier to work with.
However, I would suggest going with a multi-strand 10AWG PV cable. Should be around .33$ - .5$ per ft. PV cable has tinned copper strands and its insulation is rated for outdoor use, UV and moisture-resistant.
Also, I thought the plan was to go with a 4S2P configuration to keep it simple and avoid further expenses for a combiner box and inline fuses.
However, I would suggest going with a multi-strand 10AWG PV cable. Should be around .33$ - .5$ per ft. PV cable has tinned copper strands and its insulation is rated for outdoor use, UV and moisture-resistant.
Also, I thought the plan was to go with a 4S2P configuration to keep it simple and avoid further expenses for a combiner box and inline fuses.
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Someone suggested:
"Depending on your shading you might find trying a 2S4P setup to be more productive. Since you are running 12vDC batteries you can get by with the ~45Voc if wired that way. If you do go that direction I would suggest getting a combiner box."
I can see that there are tradeoff advantages but I don't know enough to weigh them against each other.
A. For example, I guess folks are saying that 4S2P has the advantage of not needing space-using and money-costing combiner box and inline fuses. That would be nice....
B. However, 2S4P gets more power in periodically very shady environments where some panels fall into deep shade.
IF by some miracle I actually said that correctly in the previous 2 sentences, then, because shade creeping in is such a big issue with me, I guess (unless you tell me otherwise) I'd go with 2s4P. Am I reading everybody right?
Rednecktek
Solar Wizard
Yup, you get the basic concept. Another tradeoff to going 2s4p is that because you're running about double the amps at half the volts, you're going to need heavier wires out of the combiner box and depending on the box you might need to replace the fuses inside to a 15a flavor as the 2s strings will be about 11a and often the more affordable boxes come with 10a fuses inside.
So, in a nutshell:
Pro's: Better performance in shadey areas, expansion in the future,
Con's: Higher up front cost to add equipment, requires larger wire to SCC, may require larger fuses, more wire runs required.
Many times a solar project can seem simple until shading rears its ugly head.
So, in a nutshell:
Pro's: Better performance in shadey areas, expansion in the future,
Con's: Higher up front cost to add equipment, requires larger wire to SCC, may require larger fuses, more wire runs required.
Many times a solar project can seem simple until shading rears its ugly head.
Pi Curio
Sunlicious
Yes, Mattb4's 2s4p configuration suggestion is spot on everything considered, and you seem to have a good grasp of why it's so.
All said in this thread aside, here are my thoughts.
If there's a single component that should never, ever be a subject of cutting costs in building your solar panel system, it's the heart of your system, the Solar Charge Controller.
With that said, there might be a more elegant solution to your solar installation shading challenges. Although not as elegant as 2x 400W half cut(duo panels) in the 1s2p configuration I've previously suggested, it's certainly more elegant than a combiner box and inline fuses @800W of solar.
If you go with the SCC that can work with another such SCC in a synchronized manner, you could start with a single SCC with four 100W panels in 2S2P configuration, and later, add another such SCC/panel set at your convenience.
If things have started to look more expensive and complicated with the addition of the combiner box and inline fuses for 800W of solar currently, just wait till you start looking into expanding your solar array on the foundations you've built initially if you choose to go with the combiner box/inline fuse route now.
As you've probably noticed, there's more depth to solar panel system design than what meets the eye at first glance.
Last but not least, have you already purchased your SCC?
All said in this thread aside, here are my thoughts.
If there's a single component that should never, ever be a subject of cutting costs in building your solar panel system, it's the heart of your system, the Solar Charge Controller.
With that said, there might be a more elegant solution to your solar installation shading challenges. Although not as elegant as 2x 400W half cut(duo panels) in the 1s2p configuration I've previously suggested, it's certainly more elegant than a combiner box and inline fuses @800W of solar.
If you go with the SCC that can work with another such SCC in a synchronized manner, you could start with a single SCC with four 100W panels in 2S2P configuration, and later, add another such SCC/panel set at your convenience.
If things have started to look more expensive and complicated with the addition of the combiner box and inline fuses for 800W of solar currently, just wait till you start looking into expanding your solar array on the foundations you've built initially if you choose to go with the combiner box/inline fuse route now.
As you've probably noticed, there's more depth to solar panel system design than what meets the eye at first glance.
Last but not least, have you already purchased your SCC?
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I disagree. Especially for starter systems, or small systems, a decent lower priced SCC makes much more sense than a highly expensive one. The one big issue here is where the SCC is being used. If on a mobile platform such as a boat or RV that is subject to stress from constant movement a SCC designed for this application (such as Victron) makes good sense.
No need for filet mignon when hamburger will do.
Pi Curio
Sunlicious
Is it really cheaper?
Option 1;
78$ MakeSkyBlue 60A SCC - 720W solar @12V - no further functionality expansion possible
550$ -2x 4x100W HQST Solar panels, 800W of solar
40$ - cheap 4x MC4 10A Solar fuse inline holder, most likely would need to buy 8A fuses
86$ - cheap 4-string PV combiner box
Total of; 754$
Option 2;
452$ 2x Victron SmartSolar 100V 30A SCCs, 880W solar@12V - the whole nine yards of further functionality expansion within the whole Victron ecosystem
550$ -2x 4x100W HQST Solar panels, 800W of solar
35$ 2x cheap DC circuit breaker
Total; 1037$
Summary; Option 1 is 283$ cheaper than Option 2.
With everything you know about solar @Mattb4 , would you say that option 1 is really the cheaper option going forward?
To expand further on option two, the OP could start with 400W of solar now, with no cost for MC4 Y cables by simply having 2x100W in series per SCC.
And with just another 283$ later, he could have a full-blown 800W solar without any fuses or combiner box with each 400W per SCC in 2S2P fully addressing the shading challenges he has at his installation area.
And still left with the whole nine yards of potential added functionality within the Victron ecosystem, starting with the synchronized charging between the two SCCs in regards to Bulk/Absorption/Float and general settings via the master SCC.
Option 1;
78$ MakeSkyBlue 60A SCC - 720W solar @12V - no further functionality expansion possible
550$ -2x 4x100W HQST Solar panels, 800W of solar
40$ - cheap 4x MC4 10A Solar fuse inline holder, most likely would need to buy 8A fuses
86$ - cheap 4-string PV combiner box
Total of; 754$
Option 2;
452$ 2x Victron SmartSolar 100V 30A SCCs, 880W solar@12V - the whole nine yards of further functionality expansion within the whole Victron ecosystem
550$ -2x 4x100W HQST Solar panels, 800W of solar
35$ 2x cheap DC circuit breaker
Total; 1037$
Summary; Option 1 is 283$ cheaper than Option 2.
With everything you know about solar @Mattb4 , would you say that option 1 is really the cheaper option going forward?
To expand further on option two, the OP could start with 400W of solar now, with no cost for MC4 Y cables by simply having 2x100W in series per SCC.
And with just another 283$ later, he could have a full-blown 800W solar without any fuses or combiner box with each 400W per SCC in 2S2P fully addressing the shading challenges he has at his installation area.
And still left with the whole nine yards of potential added functionality within the Victron ecosystem, starting with the synchronized charging between the two SCCs in regards to Bulk/Absorption/Float and general settings via the master SCC.
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