Description
2S 5A Lithium Battery Management System (BMS)
The 2S 5A BMS is a miniature protection circuit board designed for 2-series (2S) Lithium-ion or Lithium-polymer battery packs (7.4V nominal / 8.4V max). This board is the standard choice for small-scale, low-power applications where physical size and core safety features are the primary requirements.
Technical Specifications
| Feature | Specification |
| Compatible Cells | 2-Series (7.4V nominal / 8.4V full) |
| Continuous Discharge | 5A |
| Instantaneous Current | Typically 7A–10A (Burst) |
| Charging Voltage | 8.4V (CC/CV) |
| Overcharge Threshold | 4.25V ± 0.05V |
| Over-discharge Threshold | 2.50V ± 0.1V |
| Balanced Charging | Integrated |
| Dimensions | Ultra-compact (typically ~30mm x 10mm) |
Key Functions & Protections
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Integrated Cell Balancing: Automatically manages the charge state of both cells, ensuring they remain balanced at identical voltage levels. This is critical for preventing “cell drift,” which can lead to premature battery failure.
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Compact Safety: Designed to protect against common lithium hazards: over-voltage during charging, under-voltage during discharge, and short circuits.
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Low-Power Optimization: Ideal for ultra-portable electronics where the total power draw is relatively light, allowing for a smaller, space-saving board design.
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Common Port Logic: Simplifies your wiring by utilizing the same terminal points for both the charging input and the device power output.
Important Installation & Safety Guidelines
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Wiring Sequence (Critical): To avoid damaging the control chip, solder wires in this exact order: 0V (B-), then 3.7V (B1/Balance lead), and finally 7.4V (B+). Never plug in a balance connector while the main battery circuit is under load.
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Charger Requirements: This BMS must be used with a dedicated 8.4V (2S) Lithium charger. Using an incorrect power source will prevent the BMS from balancing the cells properly and may result in an unsafe charge.
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Thermal Awareness: While rated for 5A, avoid running the board at this limit for long periods in a completely sealed or insulated enclosure, as the MOSFETs will generate a small amount of heat that needs to dissipate.
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Wire Gauge: Because this is a 5A board, 24AWG to 26AWG wire is generally sufficient for your load connections

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