Solar panels in series: how it works

1. How to wire them

In series, the + of one panel goes to the − of the next. The − of the first and the + of the last remain free and go to the inverter (through the string box).

2. What happens

Voltage adds up, current stays the same. For example, three 40 V, 13 A panels in series give about 120 V and 13 A.

Higher voltage means less current for the same power, so thinner cables and fewer losses.

3. The most important check

Panel voltage rises in the cold. The string's open-circuit voltage must be calculated at the lowest local temperature and must stay below the inverter maximum. String calculator

For CEG systems: Growatt 6 kW up to 4 kWp per string, Growatt 12 kW up to 7.5 kWp per string (from the manuals), always within each MPPT's cold voltage and current limits.

4. Shading

In series the current is the same for all panels: one shaded panel slows down the whole string. Bypass diodes limit the problem, but it is better to keep panels with the same orientation in the same string.

5. Mistakes to avoid

• Calculating voltage in summer instead of in the cold.
• Mixing different panels in the same string.
• Putting panels with different orientations in the same string (see the east-west diagram).

6. The detailed wiring diagram

The block diagram helps you understand how it works. The detailed wiring diagram, with terminals and connections, is reserved for those who bought through Carmine Energia Gratis: write to Carmine with your CEG pre-order number. Wiring and testing must be done by a qualified electrician.

Ask for the detailed diagram All CEG diagrams

7. Frequently asked questions