MPPT is giving lower amps than other


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walter_widmore

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Sep 6, 2021
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13
Hi,

I've 2 MPPT controllers, one with 8 solar panels and one with 12.
Problem: The one with 8 panels is giving a way higher amperage than the one with the 12 panels.


Both MPPTs are in the BULK stage. I would assume I've connected them wrong but the voltage seems accurate. The panels are all installed next to each other, no shadows.

Any idea what could go wrong?
Thanks
 

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cak

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Mar 14, 2021
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132
Odd. Hard to know without digging into everything really detailed. A couple things I would check is the voltage levels at all points of the system and compare them to what the MPPT is reporting. Also couldn't hurt to check the amperages with a clamp meter just to confirm mppt readings. Assuming all the panels are working properly the only possible thing I can think of is that the output voltage is lower on the low amp controller which would lead to less of the battery load being applied to that source. Maybe they are not playing nice with eachother and so that one controller is not matching the voltage of the other. Best of luck :)
 

gpn

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Jan 21, 2018
Messages
250
Are both controllers the same victron model? Do you have the same settings? You could get a bluetooth smart battery sense and throw it on a smart network so that it reports battery voltage to both MPPTs so they are all synced together. Heck, You might want to just add both MPPT to the same smart network anyway.

Are you using the same solar panels for both arrays? If you are then maybe you should move the 12 panel array to the same series arrangement as the 8-panel array.
 

walter_widmore

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Sep 6, 2021
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I'll check the voltages & amps for each panel and per string to see if there's anything wrong with the wiring or panels.

Both are new Victron MPPTs, one is a 250/100 the other a 250/85. The 250/85 is connected to 4S2P (8) panels, the 250/100 is connected to 4S3P (12) panels. However the 250/100 is giving a lower amperage than the 250/85.

Both MPPTs are connected to a Cerbo GX so I assume that is a smart network? See entire setup scheme attached.
All panels are the same.

Thanks for the help.
 

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Patalhetas

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Oct 24, 2019
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I'll check the voltages & amps for each panel and per string to see if there's anything wrong with the wiring or panels.

Both are new Victron MPPTs, one is a 250/100 the other a 250/85. The 250/85 is connected to 4S2P (8) panels, the 250/100 is connected to 4S3P (12) panels. However the 250/100 is giving a lower amperage than the 250/85.

Both MPPTs are connected to a Cerbo GX so I assume that is a smart network? See entire setup scheme attached.
All panels are the same.

Thanks for the help.
check all the connections
and you can use the victron calculator for checking the compatibility https://www.victronenergy.pt/mppt-calculator
 

Korishan

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You could also switch input sources between the two controllers and see if the issue follows, or stays.
 

Redpacket

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Feb 28, 2018
Messages
1,392
Sounds like you have some faulty connectors or panels.
Could also be the MPPT is faulty. It interesting the "bad" MPPT number show the voltage higher, like it has unloaded the panels.
Could the settings for target battery voltage be set too low?

If the test above (swapping controllers) shows fault with panel array then maybe try the below:
Separate the 12 panel array into 3 separate strings.
Start with one panel in the string, test current (with a trusted multimeter), voltage, add a panel in series, test again, look for loss of current.
If the 8 panel array is working normally, I'm guessing one string should be measuring approx 4.45A.
The current you're apparently getting from the 12 panel array isn't even one working string?

Check the panels & look for cracks in the silicon of the cells (not good if any found).
 
Last edited:

cak

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Mar 14, 2021
Messages
132
I would agree that it reads as a hardware problem the only other thing I can think of since they are networked together is if the master controller has a max combined amp charger rate and then it is deciding to meet that rate with the small array at full and the large array finishing off to the max amps it wants. I don't even know if this is a function of those charge controllers but if they are talking to each-other or a master controller I could programmatically see them doing something like that.
 

Patalhetas

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Oct 24, 2019
Messages
28
I'll check the voltages & amps for each panel and per string to see if there's anything wrong with the wiring or panels.

Both are new Victron MPPTs, one is a 250/100 the other a 250/85. The 250/85 is connected to 4S2P (8) panels, the 250/100 is connected to 4S3P (12) panels. However the 250/100 is giving a lower amperage than the 250/85.

Both MPPTs are connected to a Cerbo GX so I assume that is a smart network? See entire setup scheme attached.
All panels are the same.

Thanks for the help.
you find the problem ?
 
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