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5S 15A Li-ion BMS Protection Board — 18V–21V, 18650 Overcharge/Overdischarge/Overcurrent
5S 15A Li-ion BMS Protection Board 18V–21V, 18650 Overcharge/Overdischarge/Overcurrent
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5S 15A Li-ion BMS Protection Board — 18V–21V, 18650, Overcharge / Overdischarge / Overcurrent
This 5S (5-cell series) lithium-ion battery management system (BMS) protection board provides complete protection for 5-cell 18650 Li-ion battery packs (18V nominal, 21V fully charged). With 15A continuous discharge current, 50–60A overcurrent protection, and full overcharge/overdischarge/short-circuit protection per cell, it is the standard BMS for 5S e-bike batteries, power tool packs, and DIY 18V/21V battery systems.
Key Specifications
| Parameter | Value |
|---|---|
| Cell Configuration | 5S (5 cells in series) |
| Nominal Pack Voltage | 18V (5 × 3.6V) |
| Full Charge Voltage | 21V (5 × 4.2V) |
| Continuous Discharge Current | 15A |
| Overcurrent Protection | 50–60A (short-circuit cutoff) |
| Overcharge Protection | 4.25–4.35V per cell (cutoff) |
| Overdischarge Protection | 2.5–3.0V per cell (cutoff) |
| Balancing | Passive balancing (variant dependent) |
| Operating Temperature | -30°C to +80°C |
BMS Cell Configuration Comparison
| Config | Nominal Voltage | Full Charge | Common Application |
|---|---|---|---|
| 3S | 10.8V | 12.6V | Li-ion laptop battery, RC car |
| 4S | 14.4V | 16.8V | Power tool battery (14.4V) |
| 5S (this listing) | 18V | 21V | E-bike, power tool (18V/21V) |
| 7S | 25.2V | 29.4V | E-bike (24V), electric scooter |
| 10S | 36V | 42V | E-bike (36V), electric skateboard |
Why Choose This 5S BMS?
- Per-cell overcharge protection — monitors each of the 5 cells individually, prevents any cell from exceeding 4.25–4.35V
- 50–60A overcurrent cutoff — instantaneous short-circuit protection prevents fire and cell damage
- 15A continuous discharge — supports 18V power tools and e-bike motors up to 270W continuous
- -30°C to +80°C — wide temperature range for outdoor e-bike and tool use
- Compact PCB — fits inside standard 18650 battery pack enclosures
Compatible With / Common Use Cases
- 18V/21V power tool battery: Replacement BMS for Makita, Bosch, Ryobi 18V Li-ion tool battery packs
- DIY 5S 18650 pack: Build a custom 18V battery pack from 18650 cells for power tools or e-bike
- E-bike 18V battery: 5S pack for small e-bike or electric scooter hub motor (18V, up to 270W)
- Portable power station: 5S 18650 pack with BMS for 18V DC output power bank
- Solar storage: 5S Li-ion pack with BMS for 18V solar energy storage system
Frequently Asked Questions
Q: How do I wire a 5S 18650 battery pack with this BMS?
A: Connect 5 cells in series: Cell 1 negative to B− (BMS), Cell 1 positive to B1, Cell 2 positive to B2, Cell 3 positive to B3, Cell 4 positive to B4, Cell 5 positive to B+ (BMS). Connect charger to C+ and C− (or P+ and P− if combined port). Connect load to P+ and P−. Never connect charger and load simultaneously unless the BMS supports pass-through charging.
Q: Can this BMS be used with LiPo cells instead of 18650?
A: Yes — LiPo cells use the same 4.2V/cell chemistry as 18650 Li-ion. This BMS is compatible with 5S LiPo packs (18V nominal, 21V full charge). Ensure the LiPo cells are rated for the discharge current (15A continuous) and that the BMS overcurrent threshold (50–60A) is appropriate for your LiPo cells’ maximum discharge rating.
Q: What charger should I use for a 5S Li-ion pack with this BMS?
A: Use a 5S Li-ion charger with 21V output voltage and CC/CV charging profile. Charge current should be 0.5C–1C of the pack capacity (e.g., 2–4A for a 4000mAh 5S pack). Do not use a lead-acid or NiMH charger — Li-ion requires a specific CC/CV profile with 21V termination voltage.
Package Contents
- 1× 5S 15A Li-ion BMS Protection Board
