Tech Tip: Avoid the Outer Limits

July 22, 2021

Operational stability and reliability of a solar power system is of paramount importance, especially for those located in remote areas. When equipment runs near minimum or maximum operational limits, system stability and reliability are compromised. Generally, it is a good idea to operate equipment in the 20% to 80% range of its operational window. Staying within that range allows some margin for exceptional occurrences, cumulative effects, and degradation due to age and/or environmental conditions.

Issues that cause system operational instability include:

  • Operating the solar array near the upper voltage limit for the charge controller. When array voltages approach these limits, charge controllers start to derate their output power as indicated by derate graphs in their operation manuals.
  • Operating the solar array voltage too close to the actual battery voltage. If the array voltage (Vmp) is too close to the actual battery voltage, a fault can occur that will stop battery charging.
  • High ambient temperatures. One can mitigate this by venting and shading the equipment enclosures. All electrical components become more stressed at high temperatures. To reduce this stress, Morningstar products are designed to derate output power above certain thermal limits as specified in the product’s operation manual.
  • Weak or undersized battery banks that can cause erratic charging system instability.
  • Under-sized or excessively long wiring that causes a pronounced voltage loss and a reduction in system performance.

Issues that cause instability in remote monitoring and data transfer include:

  • Operating data cables near the maximum recommended length for the communication protocol.
  • Streaming excessive amounts of data rather than reducing polling and data collection at longer intervals.
  • Inadequate or unstable DC voltage power on the data cables.
  • RFI interference caused by routing data lines too close to other equipment or cabling.

Just as you would not redline or lug the engine of your car, you do not want to run your solar system at the extremes either. For good service life, and stable, reliable operation, designing for a reasonable operational window is highly recommended.

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