Series vs Parallel Solar Panels: Shade, Voltage, and Current

Solar-Panel Wiring Configurations

The video compares solar-panel wiring in series, parallel, and hybrid (series-parallel) configurations. The best option depends mainly on shading, the charge controller’s limits, and the distance between the panels and controller.

Series connections

• Connect the negative terminal of one panel to the positive terminal of the next.
• Voltages add together, while current stays the same.
  • For example, three panels rated at 20 V and 5 A produce 60 V at 5 A.
• Higher voltage can reduce wiring costs because thinner cables can carry the same power.
• Keep the combined voltage below the charge controller’s maximum input voltage. The video gives 100 V as a common example for an MPPT controller.
• A series string is vulnerable to shade: the panel producing the least current can limit the current of the whole string.
• Higher voltage can help the system reach a charge controller’s minimum operating voltage sooner in weak morning or evening sunlight.

Parallel connections

• Connect all positive terminals together and all negative terminals together, often using a combiner box or MC4 branch connectors.
• Voltage stays the same, while currents add together.
  • For example, three panels rated at 20 V and 5 A produce 20 V at 15 A.
• Panels can operate more independently, so shade on one panel is less likely to reduce the output of the others.
• Parallel wiring can make it easier to add or remove panels, but connections must be weatherproof.
• Higher current may require thicker cables and a charge controller rated for the larger input current.
• According to the video, parallel wiring is common with PWM charge controllers because of their input-voltage limitations.

Hybrid (series-parallel) connections

• Combine panels into series strings, then connect those strings in parallel.
• For example, with four panels, wire two panels in series in each group, then connect the two strings in parallel.
• This arrangement can be useful when panels are divided across different areas, such as opposite sides of a boat.

Other factors to consider

• Charge-controller limits: Verify that the system meets the controller’s minimum voltage and does not exceed its maximum voltage or input current.
• Shading: The presenter recommends parallel wiring, smaller panels, or a hybrid arrangement when shading is expected. If one panel in a series string is shaded, it can constrain the string’s current.
• Panel matching: The presenter advises against connecting different panel models, saying mismatched output can limit current, voltage, and power.
• Wire length and voltage drop: Longer wiring runs increase voltage drop. A low-voltage parallel setup may fail to reach the controller’s minimum voltage if the panels are far away.
• Temperature: The video says hot conditions reduce voltage, while colder conditions reduce the voltage drop.
• Cable size: Larger-diameter wires can help reduce voltage drop, especially over long distances.

Bottom-line guidance

• Choose parallel if shading is expected or if using a PWM controller.
• Otherwise, the presenter recommends series, using as many panels in series as possible without exceeding the controller’s maximum input voltage.
• If a series string would exceed that limit, use a hybrid arrangement or another charge controller.

Speakers and sources featured

• Presenter/narrator: Unnamed; explains the wiring options and recommendations.
• Illustrations and examples: The presenter references diagrams of series and parallel light circuits and solar-panel arrangements.