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I have recently purchased a BMS rated for 3S, 40A (still in transit). Following is pictures for this BMS:

3s 40A BMS

Now, according to seller, this has over-current, over-voltage, under-voltage and short-circuit protection and 100mA balancer.

Now, After closely looking at the pictures, I couldn't find current-sense resistors on these pictures, so I am not sure how this module can provide over-current protection.

My question is: Does the pictured BMS have a current-sensor of some kind, or does it have any kind of over-current protection?

GPS
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    Please link a data sheet for the device. I mean... you bought it on the basis of what the data sheet said, yes? – Andy aka Oct 28 '20 at 14:24
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    the big 43R series resistors ? – Tirdad Sadri Nejad Oct 28 '20 at 14:24
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    @TirdadSadriNejad no.. 43R are balance discharge resistors. I am fairly certain of that – GPS Oct 28 '20 at 14:26
  • @Andyaka I don't have a datasheet. I did buy based on seller's description. I don't expect seller to be able to answer any technical questions – GPS Oct 28 '20 at 14:28
  • [What to check for when buying an electronic component or module](https://electronics.stackexchange.com/questions/504044/what-to-check-for-when-buying-an-electronic-component-or-module). – Andy aka Oct 28 '20 at 14:48
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    I’m voting to close this question because this is about a product without documentation fulfilling specifications that only the designer / seller can guarantee. You need to ask them – us figuring something out won't help you anyway. Generally, *no datasheet, no sale* is a good strategy, and the only person responsible for what you bought implementing what they promised is the seller. – Marcus Müller Oct 28 '20 at 14:53
  • You can either read the datasheet, ask the seller, or (from a safe distance) crank the load current up above 40A and find out. Or write this one down to experience and find one with data. If I had to guess I'd say it *might* have, with the current measuring shunt being implicit in either the PCB traces or (not so well characterised) the ON resistance of the FETs. –  Oct 28 '20 at 16:57
  • @BrianDrummond Thanks. In your experience, is it common to have PCB traces being used as shunt resistors? – GPS Oct 28 '20 at 17:02
  • Andyaka, Marcus Thanks. I am not looking for help in buying or matching it with the datasheet. The question was specifically, whether there is a shunt resistor somewhere on the module that doesn't look like one, or if not, is there a known way this module could've used to provide current limiting without a sense resistor. Module actually is rather irrelevant, except for being source of this curiosity. – GPS Oct 28 '20 at 17:07
  • @GPS : not common in my experience but I'm not working in that market sector. –  Oct 29 '20 at 16:41

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As it turns out, there are very similar looking BMS where some have current limiter but others don't, and then others that don't have balancer etc.

Product description of one was lingering in my head, while I had bought another different product, hence the confusion. Seller wasn't much help.. he doesn't know whats what, just that I'll get exactly whats pictured (which I did).

The current limiting ones do have two parallel R005 on B- connection in their pictures.

GPS
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