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Description
BMT 4S LITH BATT CHARGE/PROT 40AS 40A Li Ion Lithium Battery 18650 Charger Protection Board Module 18650 Charger Protection Board Module Specifications 4 string 16. 8V 40A lithium battery protection board (comes with recovery function AUTO Recovery) Scope: Nominal voltage of 3. 6V, 3. 7V lithium battery (including 18650,26650, polymer lithium battery) Product Size: 45 * 55 * 3. 4mm (Standard Edition Enhanced), 46 * 60 * 3. 4mm (balanced version) Product weight: 9. 3g (standard
S 40A Li-Ion Lithium Battery 18650 Charger Protection Board Module
18650 Charger Protection Board Module
Specifications
- 4 string 16.8V 40A lithium battery protection board (comes with recovery function-AUTO Recovery)
- Scope: Nominal voltage of 3.6V, 3.7V lithium battery (including 18650,26650, polymer lithium battery)
- Product Size: 45 * 55 * 3.4mm (Standard Edition / Enhanced), 46 * 60 * 3.4mm (balanced version)
- Product weight: 9.3g (standard / enhanced version), 10.3g (balanced version)
- Charging voltage: 16.8V - 18.1V
- Continuous discharge current (upper limit): 40A (if the cooling environment is not good, please reduce the load current use)
- Continuous charge current (upper limit): 20A
- Equalization version: suitable for starting current below 80A, power 135W below the drill.
Project Min. Typ. Max. Units Consuming current 12 18 24 uA Overcharged protection voltage 4.2 4.25 4.3 V Balanced starting voltage 4.17 4.2 4.23 V Equilibrium current 95 100 105 mA Balanced heating power 1.56 1.72 1.91 W Overcharge recovery voltage 4.1 4.15 4.2 V Over-discharge protection voltage 2.4 2.5 2.6 V Overvoltage protection after over-discharge protection 2.8 3 3.2 V Overvoltage protection after over-discharge protection 3.2 3.5 3.8 V Over-discharge recovery voltage 2.9 3.2 3.3 V Conduction internal resistance 2.5 3 3.5 mQ Overcurrent protection current C 70 80 90 A Overcurrent delay time 100 150 200 ms Continuous operating current 0 40 40 A Continuous output power 0 672 672 W Ambient temperature -40 25 85 °C
Troubleshooting: Fault phenomenon Fault check and cause The solution Unable to charge Measuring the voltage of 4 groups of batteries.
when one of the battery voltages exceeds 4.25V,
the protection board will activate overcharge protection.Pair the battery pack well, do not mix
the good battery and the bad battery.Unable to discharge Measuring the voltage of 4 groups of batteries.
when one of the battery voltages is lower than 2.7V,
the protection board will activate the over-discharge
protection.Pair the battery pack well, do not mix
the good battery and the bad battery.Charging/discharging
failureOV, 4.2V, S.4V, 12.6V, 16.8V miswired Rewire or replace the new board
(human failure, no warranty)Overcharge/overdischarge
failureOV, 4.2V, 8.4V, 12.6V, 16.8V miswired Rewire or replace the new board
(human failure, no warranty)Discharge protection Check that the battery pack has sufficient discharge
capability and check that the load's starting current
exceeds the overcurrent protection current of the
protection board.Replace the battery pack with a higher
discharge capacity, or a protective
plate with a larger current
(super working range)Component soldering There is no connection between one of the components
and the PCB pad.Repair welding Component welding There is a short circuit between two or more pins of the
component.Remove the component and re-weld Electrostatic breakdown A In the unpowered state, measure the G, D, and S
poles of the MOSFET. If the forward and reverse
resistances of any two pins are 0Q,
it indicates that it has broken down.Remove the replacement MOS tube Electrostatic breakdown B Remove the MOS tube and measure the resistance
of the G and D, G and S poles of the MOS tube.
If there is a resistance indicating that it has broken
down, the resistance should be infinite.Remove the replacement MOS tube
Package includes:
1 x Battery Protection Board
Additional Information
| Device | Protection Board Module |
| Type | 18650 | Charger Protection |
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.7 ★★★★★
Based on 632 reviews
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Product Reviews
★★★★★ 5
Comfortable and easy to set up
Color: Black, Color: Black
I’m happy with this chair. It was not hard to assemble, and it feels stable after putting everything together. The mesh back is comfortable and breathable, so it doesn’t feel too hot when sitting for a while. The seat cushion is also thicker than I expected and feels soft enough for daily use. I like the adjustable headrest and the back support, especially for working at a desk. The chair looks simple and clean, and the wheels move smoothly. Good value for a home office chair.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 1, 2026
★★★★★ 5
Exactly the Desk Chair I Was Looking For
Color: Black
had been needing a new desk chair for a while, and this one has been a great addition to my workspace. I use it every day while working, and it feels very comfortable, even when sitting for long periods of time. The seat provides good support, and the backrest helps me stay comfortable throughout the day.
Assembly was straightforward, and the instructions were easy to follow. I also like how well it fits in my workspace and how nice it looks. So far, I am very happy with the comfort and overall quality. It has definitely made my workdays more enjoyable.
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Reviewed in the United States on June 8, 2026
★★★★★ 4
very ergonomic
Color: Deep Black, Color: Deep Black
I bought this as a replacement for one of those gaming chairs that kills your back with a little lumbar pillow and this one is muuuuch better. the back support is everything you’d need and got rid of my neck pain after long periods of sitting and the seat cushion is supportive but still comfortable. It’s the kind of chair that you don’t really think about much because it’s so natural to sit in that you forget it’s there. The armrests flipping is a really nice feature too. One star off only because the head rest is so far back that i can’t really rest my head on it and every part of the chair that’s cloth is made of the same mesh texture like the armrests and seat. but i have no other complaints this is a good chair
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Reviewed in the United States on March 14, 2026
★★★★★ 5
Comfortable Ergonomic Chair for Long Workdays
Color: Black, Color: Black
I’ve been using this chair for my home office, and it’s been a great addition to my workspace. The seat cushion is thick and comfortable, even after several hours of sitting, and the mesh back keeps good airflow throughout the day. I especially like the adjustable headrest, which provides extra neck support when leaning back during breaks. Assembly was straightforward, the chair feels sturdy, and the wheels roll smoothly on my floor. The all-black design also gives it a professional look that fits well in any office setup. Overall, it’s a comfortable and affordable ergonomic chair that offers excellent value for the price.
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Reviewed in the United States on May 28, 2026
★★★★★ 3
Sturdy but uncomfortable
Color: Black
The seat itself is sturdy and easy to put together, I’ve now had the product for 8 months and had no issues wear/tear despite nearly daily use, but… it’s not comfy, at all. The seat cushion has a texture to it that scrapes at my legs if I don’t have an extra pillow on it or am wearing shorts. Additionally, the seat pillow is just kind of hard. It doesn’t give very much at all, so if I sit on it for more than an hour or two at a time my butt starts to get really sore. It works as a budget option, but invest in a good seat pillow if you plan to sit in it for any length of time.
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Reviewed in the United States on April 29, 2026