Part of the battery is not discharging when in series or parallel

This is normal behavior for batteries with BMS

1. BMS Priority and Firmware Logic

The battery's Battery Management System (BMS) uses prioritization logic to select which battery is discharged first. Some intelligent BMS systems (commonly found in modular setups) are programmed to cycle the batteries in sequence to achieve the following:

Extend life: Avoid stressing all batteries at the same time

Balance wear and tear: Prioritize batteries with the highest state of charge (SOC) or lowest internal resistance

Typically, when batteries are connected in series or parallel, the battery closest to the load's positive and negative terminals will be consumed first.

This behavior is not standard in parallel systems, but is intentional in “smart” battery design. We use advanced BMS algorithms to manage load distribution based on real-time conditions.