Premium Quality Daly 4S 12V 100A LiFePO4 Waterproof Battery Management System (BMS)

• Model Number And Year: 4S 12V 100A (Standard Common Port Edition)
• Weight: 260g (approx. 9.17 oz)
• Dimensions (L x W x H): 149 mm x 65.2 mm x 23.5 mm
• Battery Type Compatibility: Lithium Iron Phosphate (LiFePO4)
• Configuration: 4S (4 Cells in Series)
• Nominal Voltage: 12V / 12.8V
• Max. Continuous Charging Current: 100A
• Max. Continuous Discharging Current: 100A
• Charging Voltage: 14.6V
• Balance Detection Voltage: 3.50V
• Operating Temperature Range: -20°C to 70°C

Building a high-performance lithium battery pack requires robust protection to maximize longevity and maintain safety. The Daly 12V 4S 100A LiFePO4 Battery Management System (BMS) is engineered to solve the most common challenges of DIY battery assembly such as cell imbalance, voltage spikes, and environmental wear. Designed with a shared common port for both charging and discharging, this heavy-duty hardware simplifies your wiring layout while ensuring smooth power distribution.

Constructed with a premium internal chipset and high-current MOS tubes, the system continuously calculates states of health and actively manages power routing across all four cells. Its rugged, compact housing is fully injected with an advanced thermal sealant, making the unit entirely dustproof, shockproof, and waterproof. Whether you are dealing with humid marine environments, off-grid cabins, or bumpy RV trails, this board remains insulated from external stress, ensuring your energy systems stay online safely and reliably.

Features

• 100A Dual-Way Throughput: Supports up to 100 Amps of continuous charging and discharging current, matching the demands of high-draw inverters and fast-charging systems.

• Integrated Passive Balancing: Features dedicated 30mA balancing circuitry to match cell voltages automatically during charging, maximizing your pack's usable capacity.

• IP67 Waterproof Sealed Design: Encased in a fully sealed, shock-resistant housing that blocks out moisture, dust, and debris for long-term outdoor survival.

• Comprehensive 6-Point Protection: Built-in defenses guard against overcharging, over-discharging, overcurrent, short circuits, internal high temperatures, and wire disconnection failures.

• Dedicated NTC Probe: Includes an external negative temperature coefficient sensor to monitor ambient battery pack heat, halting operation if conditions become unsafely hot or cold.

• Heavy-Duty M6 Screw Terminals: Equipped with sturdy physical bolt contact points to reduce electrical resistance and prevent weak, dangerous connection points.

Applications

• Off-Grid Solar Storage: Perfect for protecting 12V LiFePO4 DIY battery banks connected to solar charge controllers and small-to-medium residential inverters.

• RV and Camper Auxiliary Power: Upgrades lead-acid coach batteries into safe, high-current lithium setups for appliances, lighting, and fans.

• Marine Energy Storage: Ideal for trolling motors, fish finders, and onboard electronics where exposure to high moisture and vibration is expected.

• Electric Mobility Support: Provides dependable battery regulation for heavy-duty electric scooters, e-trikes, utility carts, and golf wagons.

• Portable Power Stations: Forms the reliable structural core for DIY mobile generator boxes used during outdoor camping or emergency blackouts.

Usage

• Pre-Balance Your Cells: Always measure and manually balance all four LiFePO4 cells to the exact same voltage level (ideally within $10\text{mV}$ of each other) before connecting them to the BMS. The passive balancing feature is designed to maintain balance, not correct severely mismatched cells.

• Follow the Strict Wiring Sequence: Always connect the main battery negative cable to the B- terminal of the BMS first. Next, wire the voltage sampling harness starting from the total negative pole (black wire to cell 1 negative), then sequentially to each cell's positive pole. Crucial: Verify the voltages on the harness pins with a multimeter before plugging it into the BMS to prevent frying the circuit board.

• Torque Terminal Screws Securely: Tighten the M6 ring terminal bolts firmly onto the P- and B- pads. Loose connections create high resistance, which leads to localized heating, efficiency loss, and potential melting of components under heavy 100A loads.

• Observe Charging Voltage Limits: Use a dedicated LiFePO4 charger or configure your solar charge controller with a maximum bulk/absorption voltage of 14.6V (3.65V per cell). Exceeding this will constantly trip the overcharge protection loop and stress the system.

• Manage High-Current Surges: Keep your continuous load draws under 100A. While the BMS can handle brief peak surges for motor starts, sustained operation right at or above the threshold will trigger safety shutdowns to protect the internal MOS tubes.

Maintenance

• Periodic Physical Inspections: Check all physical connection points every few months—especially when utilized in high-vibration environments like RVs or marine hulls. Look for signs of thermal discoloration, loose bolts, or wire chafing.

• Keep the NTC Sensor Clear: Ensure the external NTC temperature probe remains securely attached to the middle of the battery pack (taped down with thermal or Kapton tape) and is not crushed by structural brackets or external wiring.

• Seasonal Storage Prep: If storing your battery system for the winter or long periods of inactivity, charge or discharge the pack to roughly 50% to 70% capacity. Do not store it completely empty ($0\%$) or completely full ($100\%$) to minimize chemical degradation.

• Storage Environment Management: Keep the integrated battery pack in a cool, dry location between 0°C and 35°C during storage. Even though the Daly BMS features an IP67 waterproof rating, protecting the external terminal connections from prolonged dampness prevents terminal oxidation.

• Monitor Deep Discharge Cycles: If the BMS shuts down power due to over-discharge protection ($2.2\text{V}$ per cell), remove the load immediately and apply a charge within 24–48 hours. Leaving lithium cells sitting at a completely depleted state for weeks can cause permanent capacity loss or cell swelling.