Wiring 2 Victron Smart charge controllers in parallel on PV side

[martan]

I'm not sure this was ever discussed here, most likely yes. But I'll ask anyway, I can't seem to find much about this.
I have two Victron Smart controllers MPPT 150-35, identical units and I'd like to connect my array that brings about 50-60 amps into it as 1 array. I don't want to split it and then need another set of wires for 2 smaller arrays. Is it possible to wire these controllers in parallel on PV side so they act as one unit charging with 70 amps?
Has anyone tried this?

 

[sunshine_eggo]

I'm not sure this was ever discussed here, most likely yes. But I'll ask anyway, I can't seem to find much about this.

Yep.

I have two Victron Smart controllers MPPT 150-35, identical units and I'd like to connect my array that brings about 50-60 amps into it as 1 array. I don't want to split it and then need another set of wires for 2 smaller arrays. Is it possible to wire these controllers in parallel on PV side so they act as one unit charging with 70 amps?

No.

Has anyone tried this?

Victron expressly prohibits this.

You have two controllers trying to find the optimal power output. When one makes a change, the other responds. They'll essentially fight each other perpetually never quite finding MPP. Even in a VE.Smart network, they only coordinate their output, and that doesn't help on the input.

Recommend you swap for a 150/70.

Have you left enough headroom to ensure you don't exceed 150V in cold weather?

Essentially, if you want to consistently get your peak available PV power, you need to wire to the MPPT separately or replace the two with a larger unit.

 

[martan]

Have you left enough headroom to ensure you don't exceed 150V in cold weather?

Those are 12V panels wired to 48V array, so at most I'm getting under 90V (never crossed 85V) , that's so far at least. I don't think voltage would jump over 150V.
I guess I'll have to sell at least one of the smaller ones and go for larger, I wanted to avoid doing this. They are not even a year old, like new.
Thanks.

 

[sunshine_eggo]

Those are 12V panels wired to 48V array, so at most I'm getting under 90V (never crossed 85V) , that's so far at least. I don't think voltage would jump over 150V.

If your Voc is maxed at ~90V on panel spec, you're good. 4S is good. You could go to 5S safely in most cases.

I guess I'll have to sell at least one of the smaller ones and go for larger, I wanted to avoid doing this. They are not even a year old, like new.
Thanks.

Can you imagine if you had to sell a 150/100 to replace it with a 250/100 because you didn't anticipate blowing 150V with cold temps? Asking for a friend.

 

[martan]

Can you imagine if you had to sell a 150/100 to replace it with a 250/100 because you didn't anticipate blowing 150V with cold temps? Asking for a friend.

I can't, but ask your friend if he would exchange 150/100 for two 150/35, also asking for a friend.

 

[sunshine_eggo]

I can't, but ask your friend if he would exchange 150/100 for two 150/35, also asking for a friend.

(I'm the "friend," and my wallet still hurts).

 

[martan]

(I'm the "friend," and my wallet still hurts).

I figured that much. Don't we all have these little "occasions" along the way... I guess some more than others. Don't ask me how many BMS's and cheap charge controllers I have laying around, that I will never use.

 

[sunshine_eggo]

I figured that much. Don't we all have these little "occasions" along the way... I guess some more than others. Don't ask me how many BMS's and cheap charge controllers I have laying around, that I will never use.

I call it tuition. ?

 

[RoadTurtle]

I call it tuition. ?

Big meanie!

I'm absorbing info as fast as I can, but even amongst experts, there's a lot of misleading opinions,and a lack of good industry standards. Solar is still in the early adopter stage.
.
A really good example, over paneling. My research shows this isn't a bad idea and likely gains you a total gain in total electrons. But one professional installer I talked to said he would never ever over panel, because it clips the peak output. Integrating under the curve would show that it's better to over panel. How much is too much??? Saleman I working with at BB, was insistent that it's not good. As it turns out, the best combination for me right now doesn't include over paneling, but I may try to add a panel or two later on.

 

[sunshine_eggo]

Big meanie!

I'm absorbing info as fast as I can, but even amongst experts, there's a lot of misleading opinions,and a lack of good industry standards. Solar is still in the early adopter stage.
.
A really good example, over paneling. My research shows this isn't a bad idea and likely gains you a total gain in total electrons. But one professional installer I talked to said he would never ever over panel, because it clips the peak output. Integrating under the curve would show that it's better to over panel. How much is too much??? Saleman I working with at BB, was insistent that it's not good. As it turns out, the best combination for me right now doesn't include over paneling, but I may try to add a panel or two later on.

If you don't have an ideal tilt and ideal facing in ideal sun with no shading all day long, over-paneling may be a very viable solution. Yes. One can argue there is never a good reason to not capture what's available, but MPPT aren't generally cheap, and there may be other limitations like maximum charge current, etc.

Something that gets hidden in the mess is that most MPPT end up being under-paneled because the vast majority of the time, you're not getting max PV output - 70-80% is typical. Based on real-world results, it's almost foolish to NOT overpanel by 20% just to get what you think you have coming.

 

[Checkthisout]

Overpanelling makes sense where I live.

It saves money vs adding controllers.

You're only blowing through the CC's limit late June early August and it's only a few hours a day.

Depending your needs, those are the longest, warmest days if the year when you need to energy the least.

 

[martan]

If your Voc is maxed at ~90V on panel spec, you're good. 4S is good. You could go to 5S safely in most cases.

With 5S I'm at 105V max, monitoring for 2 days now, I'm thinking adding one more shouldn't top 135 -140V in any condition.
Btw. , what happens to the Victron controller if 150V are exceeded, even if just for a quick spike ? Is it done? Cooked? Ready for new one ?
(it's probably somewhere in the manual)

 

[RoadTurtle]

With 5S I'm at 105V max, monitoring for 2 days now, I'm thinking adding one more shouldn't top 135 -140V in any condition.
Btw. , what happens to the Victron controller if 150V are exceeded, even if just for a quick spike ? Is it done? Cooked? Ready for new one ?
(it's probably somewhere in the manual)

My understanding, as it gets colder, panels will put out higher than rated voltage. Mine on the roof at 70F are exceeding published VOC, and colder will only make that worse. It's why I'm staying with parallel and using two controllers.

 

[martan]

My understanding, as it gets colder, panels will put out higher than rated voltage. Mine on the roof at 70F are exceeding published VOC, and colder will only make that worse. It's why I'm staying with parallel and using two controllers.

It is winter here and this is probably as cold as it gets here, with 5 panels I'm stable at 95-98V, occasionally jumping to 105. Maybe I'll give it a try with the 6th one. And if it fails, I'll have a reason and excuse to buy a new controller . I'll probably go for the biggest one , 250/100. Buy once cry once. I know myself, I'll be speculating and buying more panels with no stop to it.

 

[RoadTurtle]

It is winter here and this is probably as cold as it gets here, with 5 panels I'm stable at 95-98V, occasionally jumping to 105. Maybe I'll give it a try with the 6th one. And if it fails, I'll have a reason and excuse to buy a new controller . I'll probably go for the biggest one , 250/100. Buy once cry once. I know myself, I'll be speculating and buying more panels with no stop to it.

No reason to do this at my primary residence... I have room for one more panel on the roof of my 5th wheel. Going with six for now.

 

[martan]

No reason to do this at my primary residence... I have room for one more panel on the roof of my 5th wheel. Going with six for now.

Only reason, for now, is not wanting to add another set of long wires to another array. If I add a sixth panel and voltage gets dangerously high, I'll split it into 3+3 panels into 2x 36V arrays, this should max my 150/35 controller at around noon. I'll still have one set of wires going to it and 1 controller handling it.

 

[sunshine_eggo]

With 5S I'm at 105V max, monitoring for 2 days now, I'm thinking adding one more shouldn't top 135 -140V in any condition.
Btw. , what happens to the Victron controller if 150V are exceeded, even if just for a quick spike ? Is it done? Cooked? Ready for new one ?
(it's probably somewhere in the manual)

That's a never exceed voltage. Yes, there's almost certainly some wiggle room, but spec is spec. Never go over it.

If you're going to use measurements to verify, you need to disable charging and monitor voltage for the first 30 minutes after sun hits the panels.

Panels are heated by the sun, and you need to find where Voc is max when temp is min.

If your measurements are not in agreement with the specifications of the panel, but the specifications of the panel indicate you will break 150Voc

 

[martan]

If you're going to use measurements to verify, you need to disable charging and monitor voltage for the first 30 minutes after sun hits the panels.

How about monitoring it with software and logging the highest voltage of the whole array for the day, that's what I'm doing right now.

 

[sunshine_eggo]

How about monitoring it with software and logging the highest voltage of the whole array for the day, that's what I'm doing right now.

Only if charging is disabled, otherwise a draw from the MPPT will lower the voltage:

 

[martan]

Only if charging is disabled, otherwise a draw from the MPPT will lower the voltage:

Looking at Victron app, the V max for this array today was 116.07V, that's the highest of the week. Adding another panel would be getting close, but still safely under 150V I think. I'm not planning on risking it, I'll most likely make two 36V arrays from 6 panels to be safe. But just theoretically it looks like 6 panels would be doable while still keeping the voltage below 150V.