Victron 250/(70,85,100) SCC question

[cdsolar]

The Victron 250/70 charge controller has 2 MPPT trackers and can support up to 4000W of panels for a 48V system. Great. My question is, must I distribute the 4000W amongst the 2 trackers or can I have 4000W on a single tracker and not use the 2nd tracker?

Same question for the 250/85 and 250/100, can I have unused trackers but have the full wattage on a single tracker?

https://www.victronenergy.com/upload/documents/Datasheet-SmartSolar-charge-controller-MPPT-250-70-up-to-250-100-VE.Can-EN.pdf

 

[Drunkin Solar]

Those SCC's are all single tracker units. So no options for two separate strings

Edit: I misspoke....you can have separate strings but they are all on a single tracker

 

[cdsolar]

Those SCC's are all single tracker units. So no options for two separate strings

Edit: I misspoke....you can have separate strings but they are all on a single tracker

Ok, so single MPPT per device, but the MC4 models allow you to parallel strings based on the number of MC4 pairs. Got it.

 

[sunshine_eggo]

Ok, so single MPPT per device, but the MC4 models allow you to parallel strings based on the number of MC4 pairs. Got it.

and each individual MC4 connector is limited to 30A with the total parallel limited to the unit's PV input current limit (70A for the 100).

 

[cdsolar]

and each individual MC4 connector is limited to 30A with the total parallel limited to the unit's PV input current limit (70A for the 100).

But for the 250/70, for example, if you have the Tr model you can go up to 35 A for ISc, whereas for the MC4 models each string can only be 30A.

 

[sunshine_eggo]

But for the 250/70, for example, if you have the Tr model you can go up to 35 A for ISc, whereas for the MC4 models each string can only be 30A.

I feel like you're saying what I said, so I'll say this....

35A is the maximum Isc limit with each of the two MC4 connections limited to 30A max. The 35A total supersedes the MC4 limitations, i.e., 30A on one MC4 pair means you're limited to 5A on the second MC4 pair.

 

[Sun Snatcher]

and each individual MC4 connector is limited to 30A with the total parallel limited to the unit's PV input current limit (70A for the 100).

I have a question about these higher current model Victron SCCs, such as 150/100 and 250/100.

The specs say the Max. PV short circuit current is 70 A (max 30 A per MC4 conn.). For those Tr models that do not have multiple MC4 inputs, how do you get more than 30 A fed into the charge controller when running multiple pairs of parallel strings?

For example, let's say I have 400W panels with ISC (short circuit current) of 13.87A. 5 strings in parallel would total 69.35 A, just under the 70 A Max. PV short circuit current.

But, each MC4 connector can only handle 30A, so one PV wire into the charge controller cannot carry 70 A. One could combine two strings in parallel with a y-branch connector to get ISC of 13.87A times two, which combined is 27.74 A, under the 30 A limit per wire. That would mean 1 PV wire being fed to the controller with two strings in parallel.

But, I assume I could not use a 1 to 3 branch connector and parallel three strings into one wire, because ISC of 13.87 A times three strings in parallel, exceeds the 30 A limit of MC4.

So, one could have two sets of parallel strings (2 x 27.74 A) which totals 55.48 A, and then another string (not paralleled) would be an additional 13.87 A + 55.48 A totals 69.35 A, which is under the 70A total limit.

So, it would seem, to not exceed the 30 A per MC4 connector PV wire limit, I would need 3 separate wires to be fed the controller, 27.74 A + 27.74 A + 13.87 A. (all three under 30 A)

With the Victron MC4 models, for my simple brain, it appears easy to achieve. Just take the two pairs of parallel strings each combined together into one wire (using branch connector) and feed those two PV wires with MC4 connectors into two of the SCC MC4 inputs, and then take the third string which is not paralleled, and feed that into the third pair of MC4 connectors on the unit.

The unit combines (parallels) all three together, just under 70 A limit, correct? But on the Tr models with no MC4 connector inputs, but rather screw terminal connections, how do I feed three PV wires from the 5 strings into the unit? I just stack or mash all three PV input wires together and screw them all together in the one terminal connection?

 

[sunshine_eggo]

I have a question about these higher current model Victron SCCs, such as 150/100 and 250/100.

The specs say the Max. PV short circuit current is 70 A (max 30 A per MC4 conn.). For those Tr models that do not have multiple MC4 inputs, how do you get more than 30 A fed into the charge controller when running multiple pairs of parallel strings?

Please show me one. I've not seen an MC4 fit Victron MPPT what didn't have sufficient MC4 inputs to handle the rated PV input current limit with 30A limit per MC4. I know the 250/100 with its 70A input current limit has THREE MC4 pairs on it.

 

[Sun Snatcher]

Please show me one. I've not seen an MC4 fit Victron MPPT what didn't have sufficient MC4 inputs to handle the rated PV input current limit with 30A limit per MC4. I know the 250/100 with its 70A input current limit has THREE MC4 pairs on it.

Perhaps with my admittedly long verbiage, you might have misunderstood my question? It looks easy to my simple brain, to max out the 100A MPPT models (which have a max 70A limit), since there are three pairs of MC4 inputs on these.

Two strings paralleled into one, for one MC4 pair, another two strings paralleled into one MC4, going to the second MC4 input, and then another single string (not paralleled) plugged into the third MC4 pair of inputs. Three PV wires with MC4 connectors into 3 pairs of MC4 inputs on the Victron MPPT. Seems simple.

I was unsure as to how to do this with the --> Tr models <-- not the MC4 connector models. Does not Victron also make a 250/100 that only has single screw terminals for the PV wire to come in? How do I get 3 PV wires (total of 5 strings) into the charge controller?

I guess to simplify my question, can you feed more than one wire from your multiple PV strings into the Tr screw terminal PV input of a Victron charge controller (*not* the ones with MC4 inputs)?

Or is the PV input designed to take only one single PV wire?

Thanks.

 

[sunshine_eggo]

Perhaps with my admittedly long verbiage, you might have misunderstood my question? It looks easy to my simple brain, to max out the 100A MPPT models (which have a max 70A limit), since there are three pairs of MC4 inputs on these.

Two strings paralleled into one, for one MC4 pair, another two strings paralleled into one MC4, going to the second MC4 input, and then another single string (not paralleled) plugged into the third MC4 pair of inputs. Three PV wires with MC4 connectors into 3 pairs of MC4 inputs on the Victron MPPT. Seems simple.

I was unsure as to how to do this with the --> Tr models <-- not the MC4 connector models. Does not Victron also make a 250/100 that only has single screw terminals for the PV wire to come in? How do I get 3 PV wires (total of 5 strings) into the charge controller?

Assuming the 5 strings are properly fused/breakered, if the sum of the 3 wires is less than 2awg, they should fit fine.

Would prefer a combiner box solution for 5P.

I guess to simplify my question, can you feed more than one wire from your multiple PV strings into the Tr screw terminal PV input of a Victron charge controller (*not* the ones with MC4 inputs)?

Or is the PV input designed to take only one single PV wire?

It will take up to 2awg. I have 2X 8awg in mine. There might be some rule against it, but I don't care.

 

[ricardocello]

It will take up to 2awg. I have 2X 8awg in mine. There might be some rule against it, but I don't care.

Rules, schmools. Torque it down good.

 

[Brucey]

I guess to simplify my question, can you feed more than one wire from your multiple PV strings into the Tr screw terminal PV input of a Victron charge controller (*not* the ones with MC4 inputs)?

Generally for five parallel strings you would have a combiner box with breakers or fuses or in the alternative, in line mc4 fuses. You would then take the single output from the combiner and connect that single pair of wires to the pv inputs.

 

[Brucey]

Assuming the 5 strings are properly fused/breakered, if the sum of the 3 wires is less than 2awg, they should fit fine.

Would prefer a combiner box solution for 5P.



It will take up to 2awg. I have 2X 8awg in mine. There might be some rule against it, but I don't care.

Two might be ok. Would you do five?

 

[sunshine_eggo]

Two might be ok. Would you do five?

Mebbe 3x 10awg?

He's paralleled 5 down to 3 already. The concern is the insulation. The wire itself might fit, but there might not be enough room for the insulation.

 

[ricardocello]

I would say “ferrule” to shove the conductors into, but that will start an argument.
So I’m not saying it.

 

[sunshine_eggo]

I would say “ferrule” to shove the conductors into, but that will start an argument.
So I’m not saying it.

I actually wouldn't argue in that case. gotta be easier to get a 3-1 ferrule into a MPPT terminal than 3 separate wires.

 

[Sun Snatcher]

Assuming the 5 strings are properly fused/breakered, if the sum of the 3 wires is less than 2awg, they should fit fine.

Would prefer a combiner box solution for 5P.



It will take up to 2awg. I have 2X 8awg in mine. There might be some rule against it, but I don't care.

Thanks for the answers, fellas. I thought I read and saw a video where they claimed it was not necessary to fuse 2 strings in parallel, only 3 or more. So, if I have five strings total (1+1) and (1+1) and (1) fed into the three pairs of MC4 inputs of the Victron, I do not need to fuse the two pairs which are in parallel, I just plug the three PV strings directly into the unit? I would not have three strings paralleled together on any one wire, except when all five strings were joined together at the Victron.

So, if I use the exact same setup with the non-MC4 (i.e. Tr version), I should use a combiner box? So, the MC4 version of the 150/100 or the 250/100 saves me from having to buy an extra box? I just use a couple pairs of y-branch connectors to combine two pairs of strings into parallel, and then a single string, all plugged directly into the 3 pairs of MC4 inputs?

At this point all this is only hypothetical, and I am not sure I will end up having five strings fed into a 150/100 or 250/100. I just know I have a pallet of 36 identical solar panels, and I am trying to assess the best method to deploy some or all of them to snatch some photons out of the air, and convert them into electrons.

Perhaps I will arrange it differently. But I do anticipate do at least some paralleling, because I do not have the ability to line up 36 panels in series, all facing the same identical direction. Some strings will be facing a different direction, and there will be some shading for part of the day on some of the panels, but not at the same time as others.

It's good to know that I can jam more than one wire into the screw terminals of the Tr models. I anticipate using 10 AWG PV wires, so three of those would not exceed the 2 AWG size limit.

I assume I could even do 8 AWG, because 8 AWG + 8 AWG = 4 AWG, right? And 4 AWG + 4 AWG = 2 AWG, so 8 AWG + 4 AWG is smaller than that. It appears I can cram three 8 AWG wires into a 2 AWG screw terminal.

 

[Brucey]

Thanks for the answers, fellas. I thought I read and saw a video where they claimed it was not necessary to fuse 2 strings in parallel, only 3 or more. So, if I have five strings total (1+1) and (1+1) and (1) fed into the three pairs of MC4 inputs of the Victron, I do not need to fuse the two pairs which are in parallel, I just plug the three PV strings directly into the unit? I would not have three strings paralleled together on any one wire, except when all five strings were joined together at the Victron.

So, if I use the exact same setup with the non-MC4 (i.e. Tr version), I should use a combiner box? So, the MC4 version of the 150/100 or the 250/100 saves me from having to buy an extra box? I just use a couple pairs of y-branch connectors to combine two pairs of strings into parallel, and then a single string, all plugged directly into the 3 pairs of MC4 inputs?

At this point all this is only hypothetical, and I am not sure I will end up having five strings fed into a 150/100 or 250/100. I just know I have a pallet of 36 identical solar panels, and I am trying to assess the best method to deploy some or all of them to snatch some photons out of the air, and convert them into electrons.

Perhaps I will arrange it differently. But I do anticipate do at least some paralleling, because I do not have the ability to line up 36 panels in series, all facing the same identical direction. Some strings will be facing a different direction, and there will be some shading for part of the day on some of the panels, but not at the same time as others.

It's good to know that I can jam more than one wire into the screw terminals of the Tr models. I anticipate using 10 AWG PV wires, so three of those would not exceed the 2 AWG size limit.

I assume I could even do 8 AWG, because 8 AWG + 8 AWG = 4 AWG, right? And 4 AWG + 4 AWG = 2 AWG, so 8 AWG + 4 AWG is smaller than that. It appears I can cram three 8 AWG wires into a 2 AWG screw terminal.

Ultimately you would have 5 strings in parallel and need to fuse each string. You don't need ocp for one or two strings. Once you hit three strings in parallel you could have a fault in one string bring fed by the two other strings.

What panels specifically? I recently got a 250/100 and its perfect for three parallel strings of five vikram 375W panels, 15 panels and 5625W of nameplate. Voc is 41V. Mc4 inline fuses, Staubli branch connectors.

For a pallet of 30+ panels I would go with two 250/100 each with 5s3p, assuming your voltage never exceeds 250V at your record coldest temp.

 

[Sun Snatcher]

Ultimately you would have 5 strings in parallel and need to fuse each string. You don't need ocp for one or two strings. Once you hit three strings in parallel you could have a fault in one string bring fed by the two other strings.

What panels specifically? I recently got a 250/100 and its perfect for three parallel strings of five vikram 375W panels, 15 panels and 5625W of nameplate. Voc is 41V. Mc4 inline fuses, Staubli branch connectors.

For a pallet of 30+ panels I would go with two 250/100 each with 5s3p, assuming your voltage never exceeds 250V at your record coldest temp.

So, if I have this right, everyone who makes use of all three pairs of MC4 connector inputs on their Victron MPPT, in effect has at least three strings in parallel, so everyone who plugs in strings to all three MC4 pairs on the SCC, is required to have fuses or breakers on each of those three strings? But, if I only plug two strings (wired in series) to the Victron MC4 connectors, I don't necessarily need to add in-line fuses or breakers to either of those two strings?

The panels are 405W bi-facials, with VOC 37.23 and ISC of 13.87A. That's why I was asking about 5 strings in parallel, because 13.87A ISC (short circuit) times 5 totals 69.35A, which is nicely just below the 70A limit on the Victron 150/100 and 250/100s.

I may not even deploy all 36 panels. I may only use something like 18 or 24 and sell the rest off. So I am keeping my options open and exploring different possibilities.

 

[Brucey]

So, if I have this right, everyone who makes use of all three pairs of MC4 connector inputs on their Victron MPPT, in effect has at least three strings in parallel, so everyone who plugs in strings to all three MC4 pairs on the SCC, is required to have fuses or breakers on each of those three strings? But, if I only plug two strings (wired in series) to the Victron MC4 connectors, I don't necessarily need to add in-line fuses or breakers to either of those two strings?

The panels are 405W bi-facials, with VOC 37.23 and ISC of 13.87A. That's why I was asking about 5 strings in parallel, because 13.87A ISC (short circuit) times 5 totals 69.35A, which is nicely just below the 70A limit on the Victron 150/100 and 250/100s.

I may not even deploy all 36 panels. I may only use something like 18 or 24 and sell the rest off. So I am keeping my options open and exploring different possibilities.

That's correct. For two mc4s you dont need fuses or breakers. With three or more you do. But fusing is not really that expensive, $35 for 5 in line fuses:

Amazon.com

 

[Brucey]

While you could design something with 5 parallel strings its much easier to keep the amps lower and the voltage higher by going with 5s strings and three in parallel.

 

[ricardocello]

So, if I have this right, everyone who makes use of all three pairs of MC4 connector inputs on their Victron MPPT, in effect has at least three strings in parallel, so everyone who plugs in strings to all three MC4 pairs on the SCC, is required to have fuses or breakers on each of those three strings? But, if I only plug two strings (wired in series) to the Victron MC4 connectors, I don't necessarily need to add in-line fuses or breakers to either of those two strings?

Three strings in parallel, even if combined inside the MPPT on its MC4 connectors, require fuses in case a short in one of the strings causes the other two strings to dump their power through the short and cause a fire. Inline MC4 fuses, or DC breakers in a combiner box are frequently used to satisfy this.

The panels are 405W bi-facials, with VOC 37.23 and ISC of 13.87A. That's why I was asking about 5 strings in parallel, because 13.87A ISC (short circuit) times 5 totals 69.35A, which is nicely just below the 70A limit on the Victron 150/100 and 250/100s.

The only way I would do these panels is 5s3p, like @Brucey.
And get two MPPT 250/100s, that will use up 30 panels.

Unless you plan to have an east facing string, three south facing strings, and a west facing string.
Maybe I’d consider 5s5p into a single MPPT. Doesn’t seem like a good investment though.

 

[ricardocello]

And 5s3p would be rated at 6075W, which is slightly overpaneling the 250/100 assuming 48V battery,
Depending on battery voltage, you might limit at 5600W PV, with a 0.99 efficiency giving you slightly less into the battery.

 

[Brucey]

And 5s3p would be rated at 6075W, which is slightly overpaneling the 250/100 assuming 48V battery,
Depending on battery voltage, you might limit at 5600W PV, with a 0.99 efficiency giving you slightly less into the battery,

No need to worry about that slight overpanelling. In general conditions he won't be approaching those numbers, and the 250/100 will just limit output at 100A on the rare occasions it does.

 

[Brucey]

Unless you plan to have an east facing string, three south facing strings, and a west facing string.
Maybe I’d consider 5s5p into a single MPPT. Doesn’t seem like a good investment though.

I'm going with south east, south and southwest strings to try and maximize the production window versus just traditional solar noon peak.