PV String & Cold-Voc Sizing
Here is the mistake that kills charge controllers: panel voltage rises as temperature drops, and a string sized for a warm day can exceed the controller's maximum input voltage on a cold morning — permanently.
Why cold matters
Every panel has a temperature coefficient for open-circuit voltage (Voc). In cold weather, Voc climbs above its rated value. VoltForge applies the correction for your lowest expected temperature so worst-case string voltage stays inside the controller's MPPT window.
Series and parallel
Panels in series add voltage; panels in parallel add current. The goal is a string whose cold Voc is under the controller maximum, and whose operating voltage sits in the MPPT range for your battery voltage. The calculator works out how many panels in each configuration fit your chosen controller.
Common questions
What happens if Voc exceeds the controller limit?
The controller can be damaged. This is a hard limit, not a guideline — always include cold-temperature headroom.
Can I mix panel models in a string?
Not recommended. Mismatched panels drag the whole string down to the weakest panel's current. Keep a string identical.