Which Victron devices do I need for an off grid 12kW system?
- Thread starter cajocars
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sunshine_eggo
Happy Breffast!
As much as I smurf my Victron stuff, you'll never see me smurfing a Lynx product.
bds70
New Member
The BMV702 (not BMS) works fine with non Victron batteries.
sunshine_eggo
Happy Breffast!
Yep. Got one.
This is one of those cases where my BMS is more accurate than my BMV. I sync them up every so often... it's been awhile.
sunshine_eggo
Happy Breffast!
sunshine_eggo
Happy Breffast!
Also meant to mention that if I had to do it all over again, I'd have gone with the MP-II 48/5kVA... they didn't exist when I was looking for 48/5kVA.
@Adam De Lay makes me Jelly!
Adam De Lay
Solar Wizard
They are nice, especially if you don't need multiple AC INs that the Quattro has.
sunshine_eggo
Happy Breffast!
My only option for utilizing the two AC inputs are two generators. The Quattro was the only 48/5kVA option in 2019.
bds70
New Member
As someone else said, they are simply a neg/pos busbar with 4 fuse capability and if paired with a Lynxx shunt can provide a safe setup with a lot of control. That said their not strictly necessary.
When you look at some of the videos on line about large off grid systems you often see the arrangements people use. It can be useful in helping you decide.
I have been toying with changing my system to a 48v with an AIO hybrid Inverter/charger but have decided that with the quality of the Victron products, that I already have, their features and track record I am staying with them and just redesigning my battery setup keeping it at 12v.
There is so much information out there, and so many opinions etc, it can be confusing
I have learnt much from Will's video series, from Andy's off grid garage series, and from Explorist.life series and from this forum.
It's a fascinating journey.
sunshine_eggo
Happy Breffast!
I am not a religious man, but THANK GOD!!!!
green mountain boys
Solar Enthusiast
@sunshine_eggo
Could you elaborate a little more about the current limitations in light of this information from the Victron Manual Page 8 section 3.5?
"The maximum operational input current for each tracker is 18 A.
MPPT PV inputs are protected against reverse polarity, to a maximum short circuit current of 20 A for each tracker.
Connecting PV arrays with a higher short circuit current is possible, up to an absolute maximum of 30A, as long as connected
with correct polarity. This outside of specification potential allows for system designers to connect larger arrays, and can be useful
to understand in case a certain panel configuration results in a short circuit current just slightly above the maximum of the reverse
polarity protection circuit."
According to this, would it be acceptable to configure a PV string for 1 MPPT tracker that had a current of 25amps? If so, what scenario could this be beneficial given the other contraints of maximum voltage and the 4000W limit/tracker. I understand this says if you screw up and connect more than 20 amps in reverse polarity you will burn something up. I find it to be confusing because the spec sheet for this unit does not reference this 30A limit only the lower 18A/20A limit.
Thanks
Hedges
I See Electromagnetic Fields!
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Do you actually have a single PV string that puts out 25A? Or multiple strings in parallel?
Disconnect extra strings so you have a single string under the 20A limit. Connect MPPT. Confirm correct operation. Then shut off and parallel additional string(s).
That should protect the reverse-polarity protection diodes.
Of course, also confirm acceptable Voc before connecting that first string.
And confirm ~0V delta before paralleling strings.
Disconnect extra strings so you have a single string under the 20A limit. Connect MPPT. Confirm correct operation. Then shut off and parallel additional string(s).
That should protect the reverse-polarity protection diodes.
Of course, also confirm acceptable Voc before connecting that first string.
And confirm ~0V delta before paralleling strings.
sunshine_eggo
Happy Breffast!
The max the MPPTs can use is 18A each.
To retain reverse polarity short circuit protection, do not exceed 20A Isc.
If you're willing to forego short circuit protection, you can go to as high as 30A Isc.
It's effectively an over-paneling limit, i.e., if you have really shitty solar, and you want to over-panel the snot out of it, you could hang about 8600W @ 320Vmp and 27Vmp on each tracker and be within safe limits, but you would only get 4000W max per MPPT up to the maximum output of the controller.
green mountain boys
Solar Enthusiast
No, I do not have a 25A string. I am just trying to understand why Victron has designed this with the 18A/20A/30A specifications and could there be a scenario where someone would want to push the amps that high instead of splitting the string across 2 trackers.
green mountain boys
Solar Enthusiast
Thanks, I guess it would be fairly impractical to over panel that much. I was just playing around with some string designs and thought it was strange that I hit the current limit on the Victron string calculator as soon as I put a sizeable panel in parallel. I guess the Victron calculator does not allow current over the 18A/20A limit because I was certainly less than 30amps.
sunshine_eggo
Happy Breffast!
Most high voltage MPPT have disappointing PV input current limits. Victron is no different. Anything over 18A Imp is wasted/over-paneled.
One of the Growatt units had a 250Voc limit and I think a 17A PV input current limit, yet it claimed a 80A/4000W rated MPPT - there was no combination of panels that could get you to 4kW without blowing the Voc limit. It was hard to get anything more than about 3.2kW on it.
Adam De Lay
Solar Wizard
It gives you some flexibility with paralleled strings.
I wana say my panels are 11.5/12a panels so I would be wasting potential during the summer if I paralleled a few strings together, but during the winter time with more shadows across the longer strings, it seems like I could split a string of 8 into two strings of 4 to try and maximize on potential, knowing that I probably wouldn't be maxing out the amperage anyways.
While some inverters "allow" for over-paneling, they don't spell it out clearly the max amperage thats allowed for over-paneling. Victron does.
I wana say my panels are 11.5/12a panels so I would be wasting potential during the summer if I paralleled a few strings together, but during the winter time with more shadows across the longer strings, it seems like I could split a string of 8 into two strings of 4 to try and maximize on potential, knowing that I probably wouldn't be maxing out the amperage anyways.
While some inverters "allow" for over-paneling, they don't spell it out clearly the max amperage thats allowed for over-paneling. Victron does.
Daddy Tanuki
Solar Wizard
I am a magnum person myself, but once you have used tier one products taking a step backwards is well... backwards. I think you would quickly regret that move even if the inverter lasted more than 3 or 4 years. just my thoughts.
Daddy Tanuki
Solar Wizard
thats so you can over panel in locations with crappy winter solar. you would be saying goodby to a few watts in the summer but you could get up to your full 4 k watts in the winter by overpaneling. most of the tier one SCC can do this. I know morningstar has had that option since day one of their MPPT series.
green mountain boys
Solar Enthusiast
I like the Victron MPPT string calculator but I think there is some room for improvement. It took me a while to realize the calculator was not allowing strings that were possible even though you checked the box that says "allow over-paneling above 130%" The results they provide are good but they could do a better job of clearly showing the novice user exactly why the string is a failure and what can be done to fix it.
Victron should put the 30A limit on the data sheet. I would have found that a whole lot sooner if they had done that.
Victron should put the 30A limit on the data sheet. I would have found that a whole lot sooner if they had done that.
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