Series and parallel battery wiring

Battery systems often rely on combining multiple cells, but how you connect them determines the final voltage, current, and capacity. Series and parallel wiring follow simple electrical rules, yet they lead to very different behavior under load. This brief post will walk through the core differences so you can understand the impact of each configuration.

Serial battery wiring

Let's look at 4× 1.5V batteries in series connection ...

Serial Battery Wiring - it keeps System Capacity, but increases System Voltage

Wiring:  (+) [1.5V] (–) to (+) [1.5V] (–) to (+) [1.5V] (–) to (+) [1.5V] (–)

What happens:

• Voltage adds up: 1.5 V × 4 = 6 V
• Capacity (mAh) stays the same: same as one battery
• Final setup: 6 V with the same mAh capacity as a single cell

Typical use:

• Creating higher voltage: 4 AAA batteries in a flashlight to get 6V total

Parallel battery wiring

Let's look at 3× 1.5V batteries in parallel connection ...

Parallel Battery Wiring - it keeps System Voltage, but increase System Capacity

Wiring: all pluses together, all minuses together

What happens:

• Voltage stays the same: still 1.5 V
• Capacity (mAh) adds up: 3 × capacity of one battery
• Final setup: 1.5 V with triple the mAh of a single cell

Typical use:

• Extending runtime at the same voltage: triple the mAh

Summary

Connection          Result                  Explanation
4×1.5V in series    6 V (same capacity)      Voltage adds up, capacity does not
3×1.5V in parallel  1.5 V (triple capacity)  Voltage stays the same, capacity adds up

In other words 

• Serial Battery wiring keeps System Capacity, but increases System Voltage.
• Parallel Battery wiring keeps System Voltage, but increase System Capacity