7S 24V 30A Lithium Battery Protection Board

The 7S 24V 30A Lithium Battery Protection Board (BMS) is a safety and management component designed for battery packs consisting of seven lithium-ion cells connected in series, typically with a nominal voltage of 25.9V. It regulates charging and discharging to prevent battery damage and ensure long-term reliability in applications like e-bikes, scooters, and solar storage.

Key Technical Specifications:

The performance of these boards is defined by precise voltage thresholds and current handling capabilities.

• Voltage Levels: According to ariesrc.gr, standard overcharge detection occurs at 4.25V ± 0.025V per cell, with over-discharge protection triggering at 2.7V ± 0.1V.
• Current Handling: These boards support a 30A continuous discharge current. Peak or instantaneous protection current can reach 70A to handle high-start loads.
• Charging: The recommended charging voltage is 29.4V. Continuous charging current is often selectable or limited, typically up to 15A.
• Internal Resistance: High-quality boards maintain a low main circuit conduction resistance, often ≤15mΩ or ≤50mΩ, to minimize heat buildup. 

Protective & Performance Functions:

Modern 7S BMS units integrate multiple layers of hardware and software safety.

• Cell Balancing: Most 30A models include a passive balancer that bleeds off excess voltage from higher-charged cells (typically at a rate of 20-40mA) to ensure all cells reach full capacity simultaneously.
• Thermal Management: Many boards, such as those from Daly, feature NTC temperature sensors that cut off power if the battery exceeds safe limits, often set at 70°C to 75°C for discharge.
• Physical Protection: some premium versions use aluminum heat sinks or epoxy coatings for moisture and dust resistance, making them suitable for outdoor use.

Common Application:

Installation & Maintenance Requirements:

• Cell Matching: Before installation, cells must be closely matched in voltage (difference <0.05V), capacity (difference <30mAh), and internal resistance (difference <5mΩ).
• Regular Charging: Most 7S protection boards do not support 0V charging. If a battery is left discharged for too long, the BMS may not be able to "wake up" the pack without a specialized recovery charger.
• Wiring Warning: It is strictly forbidden to use these boards in series or parallel with other protection boards to increase voltage or capacity.