For battery cells, review the product description for real-world current recommendations, testing notes, and application guidance. Manufacturer maximum ratings should be treated as limits, not the best target for long-term pack health.
Description
Product Description:
Upgrade your 4S lithium-ion battery packs with this 4S 40A BMS. Designed to provide overcharge, over-discharge, overcurrent, and short-circuit protection, it includes a built-in passive top balancer, ensuring all cells reach the same voltage at the end of the charge cycle for better performance and extended battery life.
Perfect for electric tools, drills, solar storage, and DIY battery projects, this BMS is rated for 40A, keeping your battery pack safe and efficient.
Key Features:
✅ Advanced Protection – Provides overcharge, over-discharge, overcurrent, and short-circuit protection.
✅ Top Balancing (Passive Balancing) – Ensures all cells reach the same voltage at 4.2V during charging for longer battery life.
✅ 40A Current Rating – Designed for 40A applications.
✅ Wide Compatibility – Works with 3.6V/3.7V lithium-ion batteries (18650, 21700, 26650, LiPo).
✅ Compact & Lightweight – Ideal for DIY battery packs.
✅ Reliable & Safe – Prevents voltage spikes and improves battery longevity.
Specifications:
- Battery Type: 4S (4-cell) Lithium-ion (Li-ion) / Lithium Polymer (LiPo)
- Compatible Cells: 18650, 21700, 26650, LiPo
- Nominal Voltage: 14.8V nominal
- Full-Charge Voltage: 16.8V maximum
- Current Rating: 40A
- Overcharge Voltage Range: 4.25V - 4.35V ± 0.05V per cell
- Over-discharge Voltage Range: 2.3V - 2.7V ± 0.05V per cell
- Balancing Voltage: 4.2V
- Balancing Current: 30mA-50mA (Passive Top Balancing)
- Operating Temperature: -40°C to +50°C
- Board Dimensions: Approx. 60mm x 42mm x 3.4mm
Wiring Instructions:
-
Battery Connections:
- B- (B0): Connect to the negative terminal of the first cell.
- B1: Connect to the positive of Cell 1 & negative of Cell 2.
- B2: Connect to the positive of Cell 2 & negative of Cell 3.
- B3: Connect to the positive of Cell 3 & negative of Cell 4.
- B+ (B4): Connect to the positive of Cell 4.
-
Load/Output Connections:
- P- (Negative Output): Connect to the device/load negative terminal.
- P+ (Positive Output): Connect to the device/load positive terminal.
🔴 Note: Ensure all connections are secure and correctly wired to prevent damage.
Package Includes:
✔ 1 x 4S 40A BMS with built-in passive top balancer
Important Notes:
⚠ Top Balancing (Passive Balancing) – Ensures all cells reach 4.2V at the end of the charge cycle for even voltage distribution.
⚠ Not for Brushed Motors – If using with brushed motors, connect a non-polar capacitor (10µF-100µF, 25V+) across the motor terminals to prevent voltage spikes.
⚠ Do Not Short-Circuit – Ensure proper wiring to avoid short circuits and damage.
💡 Need help? Contact us for wiring diagrams or any questions about installation! 🚀
✔ Fast Shipping – Ships within 24-48 hours
✔ Trusted Seller – 100% Authentic, Tested & Guaranteed
Why Choose DIY500AMP.COM?
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Orders ship from Florida when inventory is available. Lithium-ion cells require proper handling, protected packs, correct chargers, and safe storage. Do not solder directly to battery terminals.
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