Battery Protection BMS Module (4S 40A) Teardown - Schematics, Parts List and Working

In this video, we discussed about the features and working of a 4s 40A Battery Management System (BMS), we will look at all the components and the circuitry.
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[@jacksonmgani4411]

This one was an amazing bms tutorial I have ever viewed online

[@bozmiumx]

Best most concise walk through ive ever viewed awesome work man thankyou for your efforts - subbed!

[@josepeixoto3384]

I might be wrong,man,but i think you are an engineer and you are a very good one. perfect english too that was a perfect explanation,i got it all,Thank you a video, very different from the usual utube parrot/tellers who cannot even tell the difference between A and Ah, Kw and Kwh

[@RPBCACUEAIIBH]

Very good video! 17:06 One of those 2 transistors drive the MOSFET from the CO pins, the other looks to me like a crude over current protection, limiting the current if voltage over R12 reaches BE threshold. (Not the safest since it doesn't turn off the MOSFETS so they may heat excessively. If 1 of the mosfets fails short, the battery may continue to drain in over current conditions, so I would highly recommend a main fuse anyway.)

[@qamarqamar7536]

Wow Gr8 Effort n Video,Very Well Explained👍👍👍💓💐

[@Randomname-ld1bz]

Hello, I have checked the BMS presented with the wiring diagram posted. The wiring diagram is definitely not correct. Here are a few examples: the Schottky diode D1 is at ground instead of between R4 and R36. The pinout on the PNP transistors is wrong 2/1/3 = 3/1/2. There is only one resistor / capacitance input filter for DW01 and HY2213 instead of two in parallel. The connection from R35 to ground is a short circuit. I have seen the faults without having the PCB itself and checking the contacts, there must be more faults in the schematic. The circuit diagram is totally worthless in this state.

[@lovkeshjangra674]

In my bms circuit for 2 wheeler Li ion battery, Circuit is somewhat similar, Its 1 of the 5 mos In parallel got short circuit so I removed it but the circuit still not working as the mosfets are in parallel

[@lovkeshjangra674]

Can you explain,or am I missing something

[@ronelomagtang1340]

very well said.. I smashed the subscribe button

[@lovkeshjangra674]

If one of the mosfet fails and we remove it from circuit why it does not work,as the mosfets are give in parallel

[@FranciscoSilva-qt4es]

Thanks for such a clear explanation video, I have a board HX-4S-F30A (4S 30Amps) I am connecting 4S3P 18650 battery pack to it, I can read all the correct values on each B-, B1, B2, B3, B+ ports, it comes with a P- and P+ ports as well which work as Charge and Discharge ports, it has NO additional Charging or C- port. When I connect a car break light bulb (12v , 55 watt max draw) to the P+ and P- port the bulb doesn't light up and the P ports drop the voltage to 0 and then they go back up to 11v but it never goes back up to 15-16v again. I have tried 4 boards of the exact same model and they all act the same way. It seems like the board is protecting itself but I don't understand why, since the bulb is a 12v and the current for it shouldn't be more than 10 amps, this board is supposed to handle 30A x 12v = 360w What am I missing? any help will be greatly appreciated.

[@UGPepe]

Very nice explanation! Where can I insert a thermal switch in this circuit? I think this is the only thing that this BMS is missing.

[@jochen-paulschloter5197]

Hi, thanks for best explanation. Just when i'm studying your schematics, it looks for me like there is a short between 0V and P- (watch throug Q21 base, R35, R36), regards

[@murraymadness4674]

Great video and explanation. I don't understand why there are two banks of mosfets in series? Why don't they have all 10 in parallel and control them on/off with a single line shared by the over and under voltage signal?

[@6223kerch]

Good question. Maybe maybe this could be a good improvement to the circuit :)

[@Randomname-ld1bz]

To describe it more precisely, 2 rows with 5 N-mosfets are controlled in parallel. These 2 rows of mosfets are reversed in relation to each other in order to control charging and discharging separately. If you were to connect all 10 mosfets in parallel, you can either charge or discharge, depending on how the mosfets are rotated, as the direction of current must be observed with mosfets.

[@murraymadness4674]

@@Randomname-ld1bz Mosfets have diodes that allow current to flow in one direction the other direction is switched on/off. So yeah, they use two banks so they can shut off current in both directions on/off. It is less efficient to do it this way, as you have two mosfet losses instead of one, but it makes it simpler. For discharging at high rates, this is not insignificant.

[@bzolitb]

@@murraymadness4674you have no idea how a MOSFET works, right? 😀

[@imani_ke3274]

how about adding one more feature to the board? like an auto shut off function incase the battrery is not in use...thats what im working on any limitations?

[@stinkycheese804]

I suppose it might be needed in some applications but the draw is not large. The datasheet states Self Consuming Current Min 12uA Nor(mal) 18uA Max 24uA At Max 24uA (microamps), that equals 210mA per year, which isn't very much when you consider it is meant for 18650 cells.

[@6223kerch]

Fantastic video :). I am trying to figure out how the DW01B chip is able to measure current by only measuring the voltage of the cell. Datasheet indicates this is done via measurement of voltage on the CS input compared to VSS. There doesn't seem to be a known resistance anywhere for it to calculate current from the voltage. Any ideas?

[@starelectron1509]

Very nice need schematic bms 3s 60A hw-544 Thanks 🌹

[@hedleyfurio]

great - 👍

[@dafariskiprayoga4654]

suwun lekk

[@rkanu.a]

could you please tell more detials on how to connect 1st 4 cell and then connect 2nd 4 cellls and soo on...what is the max no. of cells i can use in this particular board. waht ae requirement rues before doing that and how do you chech mah of a battery ..thank you in advance

[@doctorwho123-z1u]

Hello friend, I want to ask you something. Do we control the current in the circuit through transistors connected in series?

[@caffeineismydrug]

I have a spare 3S and 4S BMS wired up w/ 4 and 5 clip leads for bench testing and charging various laptop batteries and other packs I make. I'd love to use the CD and FD terminals for some LEDs for monitoring. I've seen references to 'Charge Detect' and 'Full Detect', but it seems they might also be used for inhibiting charging, or worse, for forcing the FETs on if used inappropriately. Thoughts on adding LEDs here? How about adding a resistor and LED in parallel with the 43ohm balance resistors to see which one is balancing?

[@louptriste493]

Hi im french man in interesed for cd and fd you are solution please

[@slavkogvozdenovic1968]

BMS 4s 16.8V does not charge batteries. I connect a 17.4V charger, but when I measure the battery, it does not charge, but stands at 15.4V. What is the cause? What parts on the board need to be replaced?

[@Circuitdigest]

Make sure you have the correct board. You can check the part numbers of the DW01 and HY2213. depending the the chip the full charge/ balancing voltage may vary. you should also male sure your batteries full charge voltage. even tough most li ion batteries have similar voltage , depending on the chemistry used that may change. please check and confirm this with the manufacturer part number.

[@johnmartin602]

What would be the maximum number of 18650 batteries one could use per series, or is there no limit?

[@MrStyle-sr1yv]

Bro thank you for the video ...question 1 : i want to charge this with 16.4 volts 4A laptop powersupply...can the bms handle this ?? I dont want to go 16.8 no need ..question 2 ...does the bms balance when the pack is not charging...meaning does it balance without reaching 4.3 volts ...say around 3.9 volts ??

[@RRmusic47]

Sir I have 4s 40amp BMS but I need to modify it 3s 40 amp . How I can Modify this

[@gurusmile839]

Very Good One , But how can we design customised bms with these components

[@stinkycheese804]

By doing it? The question makes nonsense.

[@firepower9966]

can you share your kicad schematic ?

[@deividukas]

Thank you very much for a very informative video. I was wondering if you could explain the charging circuit used (if the BMS has one)? From looking at the specifications for this circuit, would I be right in saying that the circuit uses a CV mode (of approx 16.8-17V) to charge? Typically lithium batteries utilise a CC mode to charge until it reaches a certain voltage, then moves to a CV mode (for 1S of 4.2V) until a certain minimum current at which point it stops charging and is considered full. I presume this BMS is not that smart and may require something additional to charge the cells? Again, thank you very much for putting this video together!

[@Circuitdigest]

Hi Deividar, this is just a BMS module and it cannot be used to charge your battery pack. You would have to use a saperate charger for that. however the BMS module does provide over charge protection. Yes a typical charger will have atleast two steps i.e CC and CV modes. The working of the BMS will remain the same irresptive of what BMS you are using

[@louptriste493]

Quel est la différence entre le model balance et le model enhanced thanks im french man

[@Circuitdigest]

One has cell balancing and other don't.

[@rohitraj7625]

The cell balancing here is Active or passive ? And also explain it

[@Circuitdigest]

most BMS including this one have only passive cell balancing, meaning the excess voltage in any cell is wasted using a shunt resistor. In active cell balancing the excess cell voltage is used to charge a weaker cell with low voltage this not wasting any power

[@rohitraj7625]

@@Circuitdigest but in you article you tell us that it was doing active cell balancing please check

[@Circuitdigest]

@@rohitraj7625 Just checked the article, as mentioned the module is not capable of active cell balancing, but the IC used in the module is. Meaning you can use the same IC and redesign the module for active cell balancing

[@durgaprasad-lv9cw]

Sir Your Explation Was Very Good Sir But A small Point was Missing In This Video That was near Mosfet marked As (Cd- FD ) Points what' is this Use Of That points

[@Circuitdigest]

These are test pads to check the BMS I working properly by manually providing a fault

[@durgaprasad-lv9cw]

@@Circuitdigest I'm Under Standard Ur Point but What is the Use That points

[@dimika2397]

hi, thanks for video. i build battery pack for my drill with this BMS 4S 40A, but when i push the power button drill start for 1-2 seconds and stoping. i guess excessive motor power cause this. can i fix this? What about transistor G1 near to SPARE resistor and 0V, what it do? Also your schematic missed 2 capacitors near Q and Q1 transistors.

[@MrStyle-sr1yv]

You use high drain 18650 ?? 15A discharge minimum or 10A in parallel.

[@stinkycheese804]

@@MrStyle-sr1yv How would that solve this? Your suggestion would do the opposite, make it more likely for the over current protection to kick in and cut power.

[@eshanram]

Sir I made a battery pack 4s combination with 4s 40a bms but when time of charging it is not charging properly ........ Please tell some solution of it 😔😔

[@eshanram]

Sir can I get your contact number ...... Because I have lots of questions about my battery pack

[@subkofficial90]

i just complete connecting everything.. testing the output voltage was 16.8v..but when i connect it to 550 motor.voltage suddenly become 0v...anyone can help me??

[@faraday2803]

Hello did you solved this problem?

[@doctorwho123-z1u]

Can u share this proteus project on file pls

[@Circuitdigest]

please check link in description

[@doctorwho123-z1u]

@@Circuitdigest I draw all schematic of this circuit on proteus but simulation failed can u help me please

[@MuratPALACI]

11:48 Hi, I have seen a short line on your circuit, the circuit always on charge or discharge mode. Please check R35 line, the line is always going to B- from P-

[@fear7050]

Bu durum nasıl bir sorun çıkaracaktır ? Çözüm önerini alabilir miyim ?

[@tyloscott5462]

Is anyone able to confirm this?

[@tyloscott5462]

@Circuit Digest

[@bzolitb]

I agree with others, well presented a circuit which will never work 😂 How someone can explain the operation of a circuit on a circuit which has at least 5 major mistakes? 😀

[@Circuitdigest]

Can you please elaborate on the mistakes you found. This is a popular bms used by many, i personally have tested it. But still would love to correct myself if you can Elobrate on your comment

[@jochen-paulschloter5197]

sorry, Q21 EMITTER