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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
4.4 ★★★★★
Based on 22 reviews
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Product Reviews
★★★★★ 2
Nice but runs small
Size: 7 Big Kid, Color: Navy
The sandals are nice and not to hard or flimsy but they are cut very small.
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Reviewed in the United States on April 22, 2026
★★★★★ 4
Solid Kids Sandals, Overpriced Like Most Kids Shoes 🌞
Size: 11 Little Kid, Color: Brown, Size: 11 Little Kid, Color: Brown
My son hasn’t worn these yet since it’s December in Indiana and sandals + snow obviously don’t mix. 😂 So this review is based on first impressions rather than long term wear.
That said, these seem wider than a lot of typical kids’ sandals, which I REALLY appreciate since we tend to have wider feet in our family. #hobbitfeet
The quality feels pretty decent overall. They’re described as lightweight, and while they’re not insanely lightweight, they do have enough weight to feel semi-sturdy and not flimsy or cheap. I like the style and color, and I think they’ll work well for my son once warmer weather hits.
My main complaint is the price. At just under $24 at the time of this review, it feels a little high for kids’ sandals and for what these are. I really feel like $20 MAX would make more sense. Kids shoes are almost always priced like adult shoes, even though they clearly use less material, and that’s hard for me to understand and wrap my mind around. Overall, these seem solid for daily wear, I just wish the price was a bit more reasonable and affordable.
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Reviewed in the United States on December 31, 2025
★★★★★ 5
Great basic and timeless design
Size: 12 Little Kid, Color: Brown
These sandals are a great find! They’re super easy to get on and off thanks to the Velcro straps, which is a huge win for little ones learning to be more independent. The fit is adjustable and secure, so they stay in place well during all kinds of play.
The cork-style footbed is comfortable and gives good support, and the overall design feels sturdy enough to handle everyday wear. They’re lightweight but still durable, and have held up really well so far.
They also have a classic, versatile look that goes with just about everything, perfect for summer outfits. Overall, a reliable, comfortable sandal that’s great for active kids. Would definitely buy again!
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Reviewed in the United States on April 24, 2026
★★★★★ 5
Great option for boys or girls
Size: 13 Little Kid, Color: Black, Size: 13 Little Kid, Color: Black
This is really more of a unisex option for a sandal. I have sandals that look like this, and both of my children have worn this style. I ordered these for my daughter, with the plan to pass them down to my son if they're not too worn when she outgrows them. The style is very minimalistic, so it goes with lots of outfits. All the straps are easily adjustable, so you can get a good fit. I would say the length is true to size, but the width is maybe a bit wide. Nevertheless, the adjustable straps really help them fit well. They feel really sturdy and I appreciate that the sole has cushion to it. My daughter has worn these every day since I got them out of the closet and they're holding up well.
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Reviewed in the United States on February 19, 2026
★★★★★ 5
Fast shipping
Size: 5 Big Kid, Color: Black
Good sandals, the kid just didn't want them. Fast shipping and easy returns!
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Reviewed in the United States on June 11, 2026