Paralleling slightly different panels to One Victron.

[JRH]

Going to add more panels in spring..the shade of winter is killin me… several new strings of larger panels , each string will go to its own Victron 100/50 and be totally separate on its way to the system and batts… no problem , I’m ok with this.

BUT …

I have plenty of room left for “a new string “ on the 150/ 100 CC I use now ,but I cannot find the “exact spec panels” anymore to match with the (16 panels ) I have now…bought them new 2 years ago ….they are no longer made exactly the same by renogy, for that same sized panel.
Everything is about 10% more efficient on all specs…they are still 100 watt panels ..

The old string I’m using joins at it’s combiner box /IMO / SPD etc, and feed to the 15O CC 65 ft away…it’s working fine.

. The new string (16 panels) like the old one will also be 4s4p and go to its own combiner box /IMO/ SPD etc ,and will join with the original string at the 150/100 CC in paralell….The two strings to the 150 will NOT be connected anywhere except at the input of the 150 CC , AND the bonding point of the chassis ground like all else in the system.

the 150 would be far better utilized with the new string ( slightly over paneled in perfect conditions) and way under its voltage limits In all conditions…

SO,


being the new ones are 10% higher numbers ( VOC- IMP - etc) ….will this :

1) drag the new ones down to the old ones output..?
2) combine to a new midpoint Output ...?
3) do something else I’m not thinking of…?

If I only get the production from the new ones that mirrors the old ones , I am fine with that…

Just trying to know before I buy panels after the first of the year…

Thanks J.

 

[sunshine_eggo]

Mostly #2.

#3 would be the higher voltage string discharging to through the lower voltage string giving you nothing at the MPPT.

This will typically only occur if Vmp of the higher voltage string is ABOVE the Voc of the lower voltage string.

If Vmp is less than about 10% different, should be fine. Each string will pay a 5-10% penalty vs. rated.

If you want to completely avoid the potential of #3, get an MC4 in-line diode for each string. This well prevent any potential back flow through either string. You'll lose about 1V off the string voltage due to the drop across the diode.

 

[garetwo]

Mostly #2.

#3 would be the higher voltage string discharging to through the lower voltage string giving you nothing at the MPPT.

This will typically only occur if Vmp of the higher voltage string is ABOVE the Voc of the lower voltage string.

If Vmp is less than about 10% different, should be fine. Each string will pay a 5-10% penalty vs. rated.

If you want to completely avoid the potential of #3, get an MC4 in-line diode for each string. This well prevent any potential back flow through either string. You'll lose about 1V off the string voltage due to the drop across the diode.

Would Tigo optimizers enable mixing? I need to add panels as well and cannot match existing

 

[sunshine_eggo]

Would Tigo optimizers enable mixing? I need to add panels as well and cannot match existing

No idea. Doubt it. Can you really not get Vmp within 10%?

 

[JRH]

Mostly #2.

#3 would be the higher voltage string discharging to through the lower voltage string giving you nothing at the MPPT.

This will typically only occur if Vmp of the higher voltage string is ABOVE the Voc of the lower voltage string.

If Vmp is less than about 10% different, should be fine. Each string will pay a 5-10% penalty vs. rated.

If you want to completely avoid the potential of #3, get an MC4 in-line diode for each string. This well prevent any potential back flow through either string. You'll lose about 1V off the string voltage due to the drop across the diode.

Hmmmmm ….didn’t know that… thank you…the number are as follows…the numbers are pretty tight.

old ones VOC….21.6 …( panel label)
new one VMP …20.4 … ( online….)

that only about 1 volt difference…hmmm

that’s assuming the Chinese have really taken carefull measurements to insure excellent accuracy for American customer…?

I don’t have to add this string..im adding a bunch more with different and larger panels and seperate CC‘s I already own .. I can totally live without it but it seems a waste to use about half the potential of a really nice 150/100 CC …

So the diode would be put in the positive of both old and new strings ..( total of two diodes ) is that correct ..? As in most stuff ,are there good ones and cheap ones? are they all the same ?


J.

 

[sunshine_eggo]

You technically don't need a diode in the higher voltage string. My brain likes symmetry, so that's where I go.

Sure, there are higher quality ones... probably with recognizable names. I'm very price driven on stuff like that, so I typically just order a spare of the cheap ones.

Even high quality diodes are very inexpensive. I just bought some 6A 1000V Schottky diodes to repair my benchtop power supply because my dumb ass hooked the leads up backwards to a 12V battery. The excessive forward current from the battery shorted it out, and the output of the power supply was continuously shorted through the failed diode (it's across the main (+) and (-) to prevent backflow). It's really weird to see your display read 14.4V and 10A with nothing plugged into it...

I bought 25 for something like $7.

Most of the cost in the MC4 diode is the MC4 connector itself.

 

[garetwo]

No idea. Doubt it. Can you really not get Vmp within 10%?

I just know the existing ones are no longer available. The dialogue started by JRH sparked my question. I will follow this - sorry to intrude JRH.

 

[JRH]

You technically don't need a diode in the higher voltage string. My brain likes symmetry, so that's where I go.

Sure, there are higher quality ones... probably with recognizable names. I'm very price driven on stuff like that, so I typically just order a spare of the cheap ones.

Even high quality diodes are very inexpensive. I just bought some 6A 1000V Schottky diodes to repair my benchtop power supply because my dumb ass hooked the leads up backwards to a 12V battery. The excessive forward current from the battery shorted it out, and the output of the power supply was continuously shorted through the failed diode (it's across the main (+) and (-) to prevent backflow). It's really Weird to see your display read 14.4V and 10A with nothing plugged into it...

I bought 25 for something like $7.

Most of the cost in the MC4 diode is the MC4 connector itself.

Ok last question, if the lower power string is approx 23 ish amps at 86 VOC the new string is approx 24 amps at 97 VOC .. with those numbers in mind , what amp rating or other value does the diode need to be …or is this even pertinent to this matter…

sry, but I have never bought a diode in my life…(it’s starting to sound like an electric check valve to me, but I’m just guessing.)

thanks , J

 

[JRH]

I just know the existing ones are no longer available. The dialogue started by JRH sparked my question. I will follow this - sorry to intrude JRH.

No prob…

 

[sunshine_eggo]

Ok last question, if the lower power string is approx 23 ish amps at 86 VOC the new string is approx 24 amps at 97 VOC .. with those numbers in mind , what amp rating or other value does the diode need to be …or is this even pertinent to this matter…

1.25X the Isc of the string. More is better. 30A should be fine for either.

$21 for 10: https://www.amazon.com/BAITHNA-30A-Connectors-Waterproof-Anti-backflow/dp/B0BGLN6HL7

sry, but I have never bought a diode in my life…(it’s starting to sound like an electric check valve to me, but I’m just guessing.)

Perfect analogy.

They are rated for a maximum current (gpm), and they can be overwhelmed and allow reverse flow if they experience a voltage > rated (pressure).

The 6A 1000V diodes I mentioned will block any reverse voltage 1000V and below. It can pass 6A in the forward direction.

Unlike an actual check valve, which can prevent molecules from flowing in reverse, diodes typically leak a tiny tiny tiny tiny amount of current (microamps) when a reverse voltage is applied. Like a check valve, a certain minimum pressure is required to open it, the diode consumes about 1V of potential to "open" the circuit.

 

[JRH]

1.25X the Isc of the string. More is better. 30A should be fine for either.

$21 for 10: https://www.amazon.com/BAITHNA-30A-Connectors-Waterproof-Anti-backflow/dp/B0BGLN6HL7



Perfect analogy.

They are rated for a maximum current (gpm), and they can be overwhelmed and allow reverse flow if they experience a voltage > rated (pressure).

The 6A 1000V diodes I mentioned will block any reverse voltage 1000V and below. It can pass 6A in the forward direction.

Unlike an actual check valve, which can prevent molecules from flowing in reverse, diodes typically leak a tiny tiny tiny tiny amount of current (microamps) when a reverse voltage is applied. Like a check valve, a certain minimum pressure is required to open it, the diode consumes about 1V of potential to "open" the circuit.

Truley appreciate the help , as usual…you have a great christmas, Thank you…