Solar Battery Bank Wiring: Series vs Parallel vs Series-Parallel Configurations

How you wire batteries together determines system voltage and capacity. Getting this wrong can damage batteries, reduce efficiency, or create safety hazards. Here is everything you need to know.

Series Connection

Positive of Battery 1 to Negative of Battery 2

• Adds voltage (V): Total V = V1 + V2 + …
• AH capacity unchanged
• Use when you need higher system voltage

Example: 4x 12V 100Ah batteries in series = 48V 100Ah

Parallel Connection

All Positive terminals together; All Negative terminals together

• Adds capacity (AH): Total AH = AH1 + AH2 + …
• Voltage unchanged
• Use when you need more run time at same voltage

Example: 4x 12V 100Ah batteries in parallel = 12V 400Ah

Series-Parallel (Most Common)

Series strings connected in parallel. Achieves both higher voltage AND higher capacity.

Example: 4x 2V 1000Ah cells

• Step 1: 24 cells in series = 48V 1000Ah (one string)
• Step 2: Add second identical string in parallel = 48V 2000Ah

Maximum recommended parallel strings: 4 strings (beyond this, current balancing becomes difficult)

Critical Wiring Rules

• All batteries must be identical: Same model, same age, same capacity
• Use interconnecting cables of equal length: All parallel strings must use same gauge and length cables
• Ring terminals: Always use proper ring terminals, never alligator clips
• Torque specifications: Tighten to manufacturer spec. Over-tightening damages terminals.
• Power logging: Verify with thermal camera after first charge cycle