About this video

• Video Title: Different Capacity (Ah) Batteries in Parallel - Current Sharing Explained
• Channel: Cleversolarpower by Nick
• Speakers: Nick
• Duration: 00:11:36

Overview

This video explains how current is shared between batteries of different capacities when wired in parallel. It challenges the common assumption that current is divided proportionally to capacity and demonstrates through measurements and calculations that internal resistance plays a more significant role. The video details a method to calculate internal resistance and then use conductance to determine how current is distributed, offering practical advice on wiring and fuse sizes.

Key takeaways

• Unequal Current Distribution: When batteries with different amp-hour (Ah) capacities are wired in parallel, they do not necessarily deliver current proportionally to their capacity.
• Internal Resistance is Key: The internal resistance of each battery is a primary factor in determining how current is shared. Batteries with lower internal resistance will deliver more current.
• Measurement Method: Internal resistance can be measured by calculating the voltage difference between a no-load and a loaded state and dividing by the current drawn.
• Conductance Calculation: Conductance (G = 1/R) is used to quantify how easily a battery allows current to flow. The current delivered by each battery is then calculated by comparing its conductance to the total conductance of the parallel system.
• Practical Application: The video provides guidance on selecting appropriate cable sizes and fuse ratings based on calculated current draws, considering both battery capacities and inverter efficiency.