Beginner w/8 100W 12v panels in series to chg 2 LiPo4 12v batts: 60Amp MMPT or PWM for shade?

[Mattb4]

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/Float and general settings via the master SCC.

Selectively cheery picking things to bolster your argument. The MSB at 60a can easily expand by going to a 24v or 48v battery setup. Plus even following your argument $283 dollars can buy a lot of things to use, such as an inverter or more battery capacity.

Victron SCC do not have on device screens with buttons to select features needed. You have to connect them to something else. That something else costs more money. Victron is a ecosystem who's approach is being buried somewhere in a boat or RV and monitored/controlled elsewhere. For this it makes sense to not put things you can not access directly. It also makes sense to be built to withstand the rigors and perhaps corrosive atmosphere (salt water) that being on a boat or aboard a RV would entail. However for a fixed land based setup that is not needed.

Nothing wrong with Victron, just terrible expensive for what you get.

 

[Pi Curio]

@Mattb4

We are on the same side here bro, trying to help out El Tigre with his first solar build.

Trying to teach him as much as possible about how things work and the math behind it, and suggest what we think could be the best bang for his buck going forward and why.

It's not about whos right or wrong, ego has no ground here.

I have no need to selectively cheery pick things to bolster my argument, the things I suggest are things I believe would be the most beneficial route to go with for the OP based on my humble experience with solar and the math behind my suggestion.

Goes without saying, that doesn't mean my suggestion is necessarily the best possible option for the OP, merely what I within my ability think might be a good way to go about his solar project.

We can only do so much to help, hopefully giving enough useful information to the OP so he can make as an informed decision about his solar system build as possible, going forward.

 

[Mattb4]

@Mattb4

We are on the same side here bro, trying to help out El Tigre with his first solar build.

...

Was not trying to form up sides. I try to simply put things into context. Everything needs to be examined on the merits.

In the end both of us are seeking to help out. Heck of a deal for the price.

 

[Black Pearl]

I don't remember if this what brought up yet, but the output current and/or the distance between the solar array and the SCC will require a more less specific gauge of wire.

I'm pretty sure I did it right from the get go, using a line loss chart - allowing for some expansion in the future. I used all 10g solar wire for my array, which ends shortly below the roof I have it on. I bought a kit, and made all my own custom lengths of solar wire.

From there, a quality array disconnect switch, merging into #4 fine stranded copper for about ~35 - 40 feet (in conduit) to the SCC.

I have another SCC disconnect inside my garage where the rest of my solar gear is located.

I used mc4's for everything on the roof, and eventually utilized 15 amp inline fuses when I exceeded 2 series strings into parallel. I currently have 4s4p, but began with 4s2p. All 12v 100 watt panels.

It all adds up...

Side note... My latest 4s4p system charges like a champ, compared to the former 4s2p setup. My charging rate more than doubled, and I doubled my LiFePO4 battery bank capacity during my last upgrade.

Still learning...

 

[Rednecktek]

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 Included with combiner box
106$ - cheap 4-string PV combiner box
Total of; 734$

Fixed the math there, the combiner box comes with the fuses and DC breaker so no need for inline holders.

One piece of advice I like to give is that if you think you're going to break something, break a CHEAP something. In this case it really isn't a life-or-death-full-time-living-off-the-grid situation so spending nearly $300 more on Victron equipment then having to spend all the extra for Victron only compatible equipment at their markup really gets into $$RealMoney$$ fast. The difference between going cheap and simple even with your basic Victron system is the difference of a whole 100Ah LFP battery. The price of a single Victron 30a is on par with a mid-tier 60 or 80a SCC, so not a great value for the I'm-there-once-in-a-while-camping-shack.

Is dropping $$StupidMoneys$$ worth the return for the use case? The OP is very much on a budget trying to get the most value for the dollar and "Budget" and "Victron" tend to be mutually exclusive terms. If the budget wasn't an issue and this was the primary system keeping your life working and your fridge running 24x7 reliably and your water flowing then Victron might (and I say MIGHT) be a very good option for the peace of mind of a higher chance of everything just working. With the fact that it's basically a camping getaway and only used a few days a month at best, adding in that getting around the inherent paywall of solar exists to begin with, it just doesn't seem like going Victron is worth the extra cost in this use case.

But that's just my opinion, what do I know?

 

[Pi Curio]

Fixed the math there, the combiner box comes with the fuses and DC breaker so no need for inline holders.

Not quite there yet, did you account for the additional cost of additional cabling and cable sizes?

One piece of advice I like to give is that if you think you're going to break something, break a CHEAP something. In this case it really isn't a life-or-death-full-time-living-off-the-grid situation so spending nearly $300 more on Victron equipment then having to spend all the extra for Victron only compatible equipment at their markup really gets into $$RealMoney$$ fast. The difference between going cheap and simple even with your basic Victron system is the difference of a whole 100Ah LFP battery. The price of a single Victron 30a is on par with a mid-tier 60 or 80a SCC, so not a great value for the I'm-there-once-in-a-while-camping-shack.

Is dropping $$StupidMoneys$$ worth the return for the use case? The OP is very much on a budget trying to get the most value for the dollar and "Budget" and "Victron" tend to be mutually exclusive terms. If the budget wasn't an issue and this was the primary system keeping your life working and your fridge running 24x7 reliably and your water flowing then Victron might (and I say MIGHT) be a very good option for the peace of mind of a higher chance of everything just working. With the fact that it's basically a camping getaway and only used a few days a month at best, adding in that getting around the inherent paywall of solar exists to begin with, it just doesn't seem like going Victron is worth the extra cost in this use case.

But that's just my opinion, what do I know?

Look, I don't understand why some might have an issue with the Victron.

They have the largest portfolio of available SCC sizes for all sorts of possible use cases, all it takes is to dig deeper into the math and evaluate what might be the most economical and beneficial route to go with going forward. Period.

I make the component selections based on math, cost, budget, use case, solar conditions for a given installation, plans on further expansions, whether there are components already bought/in use, and so on and on.

As long the math supports it, I will suggest Victron anytime any day.

When I make a suggestion to the OP I'm trying to help, his interests are my only priority.

El Tigre doesn't have to settle for a 'budget' system. With a bit of pacing over a period of time, incrementally, with the additional 286$ ish down the line, he could have a high-quality system as far as the solar side of it is concerned. I'm merely trying to point that out to him.

In short, let's agree we disagree on this one.

 

[El Tigre]

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.

Welp, remaining decisions may be simplified since, with initial purchases, I seem to have gone closer to option 1.
1. I bought the very nice MakeSkyBlue 60A-V119 (see sketch below)
https://makeskyblue.com/products/60a-mppt-solar-charge-controller-w-wifi?variant=31426587918470
2. I bought 4 100W panels for an initial test with 2S2P (then will add 4 panels to go to 4S4P--sketch below is 4S2P)
https://www.amazon.com/HQST-Monocrystalline-Efficiency-Charging-Applications/dp/B095WRXB55/ref=sr_1_20?keywords=watt+solar+panels&qid=1679800734&refinements=p_72%3A2661618011&rnid=2661617011&sr=8-20&ufe=app_do%3Aamzn1.fos.ac2169a1-b668-44b9-8bd0-5ec63b24bcb5
3. I bought a half dozen MC4 connectors (male & female)
https://www.amazon.com/gp/product/B073TX1N5Q/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&th=1
& 2 Y-adapters (at right in sketch below)
https://www.amazon.com/BougeRV-Connectors-Branch-Parallel-Adapter/dp/B0753X68PS/ref=pd_bxgy_img_sccl_1/146-9103404-9796832?pd_rd_w=yh8Sf&content-id=amzn1.sym.6ab4eb52-6252-4ca2-a1b9-ad120350253c&pf_rd_p=6ab4eb52-6252-4ca2-a1b9-ad120350253c&pf_rd_r=HY1ERD0FXAFGA1TVPGVN&pd_rd_wg=eXYSO&pd_rd_r=16cef64d-8544-4a37-9dcd-1433631ea847&pd_rd_i=B0753X68PS&th=1
4. & I guess I will now need to buy at least 1 15A fuse (based on what I'm hearing from the helpful hints here).
https://www.amazon.com/PowMr-M-C-4-Waterproof-Line-Holder/dp/B08C26GJGQ/ref=psdc_6355937011_t1_B08L5771XR?th=1
Seems like I heard fuse references in the plural but it would seem that one fuse would break the circuit.
A. Do I need 2 (just 1 in sketch)? B. IF I just need 1 fuse, is the red (positive) the one to be fused? C. 15Amp or other fuse?
D. Do I need a combiner box and or switch? (and, if so, any suggestions?...think already over budget )
You are so right that there is a lot to know ! (Sketch below)

 

[El Tigre]

......also...Using 10AWG wire.

 

[Pi Curio]

2. I bought 4 100W panels for an initial test with 2S2P (then will add 4 panels to go to 4S4P--sketch below is 4S2P)

At 4S4P you'll need the combiner box, with additional expenses for cabling and obviously, the only option, you'll need to switch to a 24V system voltage to have any use of the additional 8x 100W solar panels because your SCC hit the limit at 720W and it can't work with another SCC in a synchronized manner.

Unfortunately, this probably means you'll need to buy a new, 24V inverter.


I guess either that or getting a new, bigger SCC, or at least one that can work in parallel with another SCC.

4. & I guess I will now need to buy at least 1 15A fuse (based on what I'm hearing from the helpful hints here).
https://www.amazon.com/PowMr-M-C-4-Waterproof-Line-Holder/dp/B08C26GJGQ/ref=psdc_6355937011_t1_B08L5771XR?th=1
Seems like I heard fuse references in the plural but it would seem that one fuse would break the circuit.

The diagram you've shared below is for a 4S 2P configuration, the one you previously said you are interested in was a 2S 4P because of the shading challenges at your installation.

With that said a single 15A inline fuse on the main can be beneficial in a 4S 2P configuration.

A. Do I need 2 (just 1 in sketch)? B. IF I just need 1 fuse, is the red (positive) the one to be fused? C. 15Amp or other fuse?

If you want a fuse there, you need only 1, on the positive(red), 15A is above the combined 4s2p Array Isc so it won't accidentally trip when used there.

D. Do I need a combiner box and or switch? (and, if so, any suggestions?...think already over budget )

The combiner box is essential only when you go with the previously mentioned 4S4P eventually.

Would suggest at least having the means to disconnect the PV from the SCC, a simple properly rated DC double pole circuit breaker in between the SCC PV input and the solar main cables would do.

You are so right that there is a lot to know ! (Sketch below)
View attachment 145071

 

[El Tigre]

oops...that is correct...I sent the wrong sketch...I plan to start out 2S2P and, assuming that works, add 4 more panels and set for 2S4P. (should delete old out of date sketches; sorry that one got sent) Will send 2S4P sketch

 

[El Tigre]

Ignore previous message for now...reviewing posts...

 

[Black Pearl]

At 4S4P you'll need the combiner box

I used all mc4 branch connectors on my 4s2p system, and when I upgraded to 4s4p, I am still well within the limits of the mc4 branch connectors themselves (30a). I could add another identical series string (4 panels), and still be within the limits of the mc4 branch connectors.

At that point, I'd be 4s5p, but I wouldn't chance that with my current SCC, with all those panels facing the same direction as they are now.

Yeah, I obviously did upgrade to a 24v system, and my original SCC supported that upgrade. In hindsight, I wish I would've started out on that platform, mainly due to the cost of LiFePO4's. Live and learn...

I agree with others that LiFePO4 batteries in parallel is the way to go, and I ended up with 4 12v 200ah BMS LFP's (2s2p) during my recent upgrade. I haven't got around to installing the 2 12v balancers I recently bought, but I really didn't seem to have a more reasonable choice when it came to the decision of what to do with my original pair of 12v LFP's. 2 new 24v 200ah LiFePO4's would've set me back another ~3k...

I ended up buying 3 24v inverters, but only utilize 2 of them.

Some of what I am describing is what people that have been through all this are trying to save others from having to go through.

It's all good though. I learned a lot of stuff hands on in the process - which is priceless.

 

[Mattb4]

At 4S4P you'll need the combiner box, with additional expenses for cabling and obviously, the only option, you'll need to switch to a 24V system voltage to have any use of the additional 8x 100W solar panels because your SCC hit the limit at 720W and it can't work with another SCC in a synchronized manner.

Unfortunately, this probably means you'll need to buy a new, 24V inverter.


I guess either that or getting a new, bigger SCC, or at least one that can work in parallel with another SCC.



...

You can add more SCC (with their own PV array) to a battery bank without them needing to be synchronized other than establishing charge profiles. Paralleling DC output devices is not a big deal. You can parallel batteries easily of the same voltage and different amperage. Just like you can charge batteries with multiple chargers so long as you do not exceed battery max charge amperage. Incidentally AIO's run both a MPPT SCC and charging via AC at the same time if you want it.

So while not going 4S4P you can easily go 2 SCC with their own 2S4P arrays feeding the same battery bank.

 

[Pi Curio]

@Mattb4
I stand corrected.

For some reason I was under the impression that two SCCs might fight each other at different charging stages.

Learn something new every day


That quite literally changes the math.

I guess instead of spending budget on the combiner box he could get another such SCC, having 4 panels in 2s2p per SCC.

For the cost of this SCC, that would pretty darn nice setup.

 

[Mattb4]

@Mattb4
I stand corrected.

For some reason I was under the impression that two SCCs might fight each other at different charging stages.

...

Interesting enough in my system that has a second array of 800w, utilizing a 30a MSB feeding the battery bank, it acts to help with overall solar production because it floats while the AIO has turned off charging from the 1200w Main array (sometimes at 1pm on a good sun day) after reaching full charge.

I have the MSB set to charge to .2v less than the AIO. (BTW I had to calibrate voltage reading on the MSB to match my DMM and AIO, it does have a calibration feature in the programing mode which my AIO does not) The sequence seems to be both arrays work at max watts available until the MSB reaches the voltage limit I set for it and shuts down production. The AIO however keeps charging until it concludes full charge and then it shuts down charging. Loads bring battery down to below the MSB voltage and it begins drawing enough wattage to supply loads while holding battery charged. That is usually in mid to late afternoon. During late afternoon into evening, if loads bring my batteries below the AIO's Fully charged recovery voltage, both arrays will output so solar production is not lost and the battery bank has more of a charge when going into night.

You do want to tinker a bit with charge settings for how each SCC goes in and out to get your best overall solar yield.

The units that are designed to synchronize eliminate the need to tune outputs since they act together. This is the principle behind SigSolar's Chargeverter. Inside of it is two 50a chargers that output a combined 100a.

 

[El Tigre]

Thanks!
Here's a spreadsheet I did just to quickly "see" what my options look like.
If you see errors, I'm still a dummy! (If you can use the .xls, let me know. It's meant to calculate results for any values you plug into the blue part of line 5).


So, if, after I set up a 4S2P layout (in line 9 above and sketched below), it looks like the best I could do if I wanted to still avoid a combiner box by staying with 2 runs (though do plan to have a 15 amp fuse...see below), the best I could add on without a combiner box would be 2 100W panels for 5S2P.

Do I understand this yet?
Still a beginner,
John

 

[Rednecktek]

Yup, looks good!