How can I connect strings in parallel?

How can I connect strings in parallel? Connecting strings in parallel can be useful to connect more power to a single MPPT input of an inverter. However, to do this safely and effectively, there are a few key rules you need to follow. An incorrect setup can cause power losses or even damage to the system.

Important conditions for parallel connection

• Same type of solar panels

  Always use panels of the same brand and model, with identical specs and wattage. Never mix different panels in the same setup.

• Equal string length

  Make sure each string contains the same number of panels. Uneven lengths cause voltage differences, which creates problems when connecting in parallel.

• Same orientation and tilt angle

  All panels should be installed on the same roof surface, with the same orientation and tilt. Differences will lead to mismatches and reduced yield.

• Avoid shading

  Shading on one of the strings will affect the performance of the other string when connected in parallel. Only connect in parallel if there is no shading—or minimal shading at most.

Technical checks

• Check voltage

  Verify that the Voc (open-circuit voltage) stays below the maximum allowed by the inverter. Use the manufacturer’s string configurator to calculate this.

• Check MPP range

  Make sure the Vmpp (minimum and maximum MPP voltage) of the string falls within the inverter’s operating range.

• Check current (Idc)

  With two parallel strings, the inverter must handle double the current. For example: if one string has an Impp of 11A, the inverter must handle at least 22A.

Questions or doubts?

Contact our technical After Sales team at +31 (0)88 88 80 320 or email us at customersupport@libra.energy. We’re happy to help!