Dazu finde ich bei Victron keine Angaben.
All Victron mppts have a max voc and a max isc rating. (Should have temp co efficients apllied) Both are hard limits.
All datasheets and mppt tech specs have a max input short circuit rating.
100/30 tech specs state max isc 35A.
250\60 tech specs. 60A isc
A higher short circuit current may damage the solar charger in case of reverse polarity connection of the PV array.
Who cares ?
Also in the case of if battery over charge protection is triggered.
The victron mppts actually short the input in a number of scenarios, so it does matter the total isc of the incoming pv strings.
I think a warranty claim will make someone care.
Where do you find this information, in all cases it should be sufficient to turn of the tracker, in no way is an mppt able to burn 100es of watts
It shorts the pv input when there is over charge detected. Or to prevent charging all these ones.
One off the top of my head error 29.
And the datasheet/tech specs says there is a max …
The input protection works as follows:
If the rated input voltage is exceeded (by a small threshold) the a FET is turned on to clamp the input.
This is to protect the MPPT’s switching FETS, which could otherwise be destroyed by the over-voltage. The result of this type of failure would connect the battery directly to the Solar modules - via a fuse.
So the Max input current must not exceed the power /current rating of this clamping FET.
There is no great power dissipation, as the input voltage drops to near zero from the PV. The fet is a few 10’s of miliohms when on, so power dissipation is only a few watts.
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Too many iffs.
If i have fi a 100 mppt and 80v pvmax this situation will never occur.
The max current has a footnote specifying this for reverse voltage.
For a 48v system its almost impossible to meet these restrictions
All these errors are reactions to malfunctioning of the mppt.
And most have been corrected with updates and newer versions.
If there is a problem with the battery (and it can happen particularly with lithium) the mppt will short its input. Still happens in the field.
I tech supported a site not even 2 weeks ago that had a fault and the pv input was shorted. One failed because the person over paneled too high an isc. (No warranty). The other mppt was fine resumed working when the battery voltage came down.
Not all are mppt problems.
I don’t understand how we got into this discussion, with 4 seperate strings of 2 panels in series as the to specified and 4 100/30 mppt’s the system is well within all specifications
Hi. Interesting discussion. Just wanted to give my honest opinion. I don’t quite want to fill one side of my wall with 4 different MPPTs, it also sounds much more complicated. What I decided, is just going for 1 150/45 unit, or 1 250/85 unit.
I just found out that the 250/85 can be connected with two different strings (4 mc4 connectors). My theory is, I would be able to connect some of my solar panels in series while others in parallel, in that case, the voltage of one array would remain the same, but the amperage would increase. While the other array, wired in series, would just add up voltage that wouldn’t exceed the MPPT’s original specification.
Let me know what you think. I am still considering the 150/45 unit. I wonder how many watts could I expect to pull from it with three solar panels (according to Victron calculator).
If you want all your panels on one mppt, the most ideal set up is to keep the voc the same for both strings.
There are two mc4 connections but they don’t track differently, you will lose power there.
You don’t list your temp coefficients so can’t help with specifics.
Your original thread is still here. I was trying to keep the topic from digressing.
The 100/30 is very small compared to a 250/xx,
there is nothing complicated about it, just a bit more wiring.
Hi. The temperature coefficients of each panel are:
Temperature Coecient (Pmax) -0.29 % / °C
Temperature Coecient (Voc) -0.25 % / °C
Temperature Coecient (Isc) 0.05 % / °C
Understood. Just to make things clear, you believe that by using four of the 100/30 MPPTs, I would have a larger watt input from my solar panels compared to using just a single 250/85 unit, that would only work with 5 panels. Correct?
Could I wire the 4 strings in series? Thank you.
1: 85 Amps output @ 24V = ~2000W, your 8 panels have a total of ~3400W that can be fully used with 4 100/30 MPPT’s at lower cost.
2: NO
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Thanks for sharing more details on the power output. How should I wire each 4Ă—2 strings then, in parallel?
No, series is easier
Let me add my 2 cents to the original question.
Direct / correct connection:
The entire PV panels ensemble / array, no matter how is built, has a resulting ISC.
When the MPPT scans for maximum point, it must explore the entire V/I curve of the array.
This means that, at some point, it will “shorten” the array and the array will pump its max current.
The FETs inside are sized accordingly with that max ISC the MPPT can handle. So better not exceed it.
Inverse / incorrect connection:
A normal FET has a reverse diode protection inside.
When the array is connected in a reverse manner, that diode is in direct conduction.
So all the energy that the array can generate is “shortened” by that diode. The MPPT will heat up but will not function.
The parameters of that diode are also a characteristic of the chosen FETs inside MPPT. So better not exceed those parameters.
So, you see, you either exceed the switching parameters of the “harvesting” FET or you exceed the reverse diode parameters inside the FET.
Neither is good, so the max ISC of an MPPT, being a consequence of the chosen electronic components inside, really matter… 