Overview of Over-paneling an MPPT controller

Overview of Over-paneling an MPPT controller 2021-10-21

There is a misconception that putting more panels on an MPPT controller than the controller is able to use will damage the controller. However, in almost all cases it is possible and often desirable to put more panel wattage onto an MPPT controller than the controller is rated to use. This is called over-paneling

This paper is a high-level discussion of what over-paneling is, why it is useful and how it works.

A shout out to the following forum members for review and comment of early drafts:
@fafrd
@Randij
@wattmatters
@Will Prowse

As usual, if you have suggestions or corrections, please let me know so I can improve the resource.

Revisions:
9/30/2021 - Original Version.
10/18/21 - Added details for Victron and EPever controllers.
10/19/21 - Added specifics for Midnite Solar Classic controllers.
10/20/21 - Added specifics for Sol-Arc, Schnider Electric Conext, and Growatt controllers.
10/20/21 - Add a page with a discussion of controllers that limit the Array Isc.
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FilterGuy
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This is really a good paper!
Thanks for this. I am thinking about Way Over-Paneling a Classic 150 soon.

I am making a post about what I want to do and would appreciate any feed back so I do not make a huge mistake. I have not ordered anything yet.

https://diysolarforum.com/threads/over-paneling-a-3s3p-to-3s5p-with-slightly-different-panels-advice.29838/
Very usefull. Just a comment: victron states in their manual:

There are two limits, when determining the maximum array size that can be connected to an MPPT:

The Maximum PV open circuit voltage (Voc at STC)
The Maximum PV short circuit current (Isc at STC)

-> so so max overpaneling on victron MPPTs is most limited by the short circuit current. You can find the Isc at STC in every MPPT manual. One thing is interesting: the short current is the same for one series of MPPTs. e.g. 150/45 to 150/70 -> all have 50 amps max PV short current.

Jens
FilterGuy
FilterGuy
Previous Reply was deleted and replaced by this.

After additional research and communication with Victron, it has become clear that the Max Isc spec comes into play in more scenarios than just reverse polarity on the PV inputs. Victron has declined to elaborate on the additional scenarios but has made it clear that the scenarios exist. So, even though Victron has called the Max Isc spec a 'Soft limit' the designer has no choice but to treat it as a hard limit.

I have updated the resource to add pages with Victron specific information and how to deal with the Max Isc spec.
Good explanation and graphics.

Over paneling works with my VIctron 75/15 MPPT. I use 600 watts of panels to over-panel my 360 watt SCC and move the panels along with the sun to max charging.

I limit charging to 14 amps due to BMS limitations. For me, I want my panels to replace energy a 300 watt load consumes and still have a little left over to charge the battery.

Overpaneling does work in this application.
Extremely helpful for a confusing topic. Thank You!
Concise, easy to follow. Puts the topic to rest
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