MPPT Controller Picker

How do I find the temperature coefficient?

Check the panel datasheet for “Voc temperature coefficient” (e.g., −0.30%/°C). We use its magnitude to increase Voc as temperature drops. If unknown, 0.30–0.35%/°C is a conservative estimate for many 60/120-cell modules.

What margin should I keep below Vmax?

Aim for at least **5–10%** headroom under the controller’s absolute Vmax. This covers meter error, panel tolerance (+Voc), and unexpectedly cold mornings.

What if my cold Voc exceeds the controller Vmax?

Reduce **series count (S)** or choose a **higher-voltage MPPT** class (e.g., move from 100 V to 150 V). Never rely on “it probably won’t get that cold.”

Does parallel increase Voc?

No. **Series** raises voltage; **parallel** raises current. Parallel affects **Imax** on the controller input; series affects both **Vmax** (cold) and **operating Vmp**.

Why check Vmp vs MPPT window?

Controllers track best when **string Vmp** sits **within** the window (above Vmin, comfortably below Vmax). Too low and you’ll stall; too close to Vmax and you risk clipping or shutdown in cool, bright conditions.