BMS  "overcurrent protection 60A" - Page 1
Forum section: electronics / projects

author: davisdesigns
author_rank: Contributor
timestamp: February 05, 2022, 04:36:28 am
content: Too much information on my first post apparently here's a simple question. Does this BMS protect i.e. Disconnect the load from the battery if the load exceeds 60A and by disconnect I mean not destroy the BMS..https://www.amazon.com/dp/B08PTWGD7H?ref=ppx_yo2_dt_b_product_details&th=1When they say "overcurrent protection 60A" if I draw more than 60A i'm under the impression that the BMS will turn the FET's off. Is this a correct assertion ?Futures:100% Brand new and high quality 18650 lithium battery charging ModuleFOR Li-POLYMER LiMnO Protect Parameter(3.6V/3.7V)Single Cell overcharge protect voltage: 4.23 - 4.28VSingle Cell overcharge rotect recover voltage: 4.08 - 4.18overcharge protect delay: 0.5 - 1.5SSingle Cell over-discharge protect voltage: 2.72 - 2.88VSingle Cell over-discharge rotect recover voltage: 2.9 - 3.1Vovercharge protect current: 60Aover-discharge protect current: 60Aover-discharge protectdelay: 0.5 - 1.5Stemperature protect: YESdisconnect protect: YESshortage protect: YESshortage delay: 100 - 600μSshortage protect recover: YESCharging current: 25Adischarging current: 25Acharging voltage : 12.6V for 3S , 16.8V for 4S, 21V for 5S BMS boardthe video in this page is demonstrated for BMS 5S

author: Psi
author_rank: Super Contributor
timestamp: February 05, 2022, 05:10:33 am
content: Quote from: davisdesigns on February 05, 2022, 04:36:28 amThat would be my understanding, Yes.But it usually isn't immediate if you are only just over the limit, there will be a short delay. And some error in the measurement. Might happen at 58A or 65A etc..

author: davisdesigns
author_rank: Contributor
timestamp: February 05, 2022, 07:10:28 am
content: When I tested a stall load on the drill i got 75A before the protection cut.I switched to thick gauge and shorter wires after testing so I suspect the amperage exceed the test but the data sheet says peak is 200Ahttps://radioremont.com/wa-data/public/shop/products/14/40/4014/attachments/KIA50N03A.pdfWonder if its just the cheap FET's that maybe is the culprit and might be worth finding quality replacements or just chalk this BMS up as another junker sold on AmazonWish I could find a simple hi amp lipo 4s discharge protection board

author: Psi
author_rank: Super Contributor
timestamp: February 06, 2022, 01:59:18 am
content: The way they measure current is usually pretty cheap/crude and not very repeatable from one unit to another (the spread is wide). They usually make sure the limit will always be over the stated trip current.Since less people complain when it trips 10A above the limit verses 10A below the limit.The overcurrent trip current isn't really meant to be used as part of your circuit. It's mean to protect things in the case of a short circuit or massive overload.

author: uer166
author_rank: Super Contributor
timestamp: February 06, 2022, 03:40:29 am
content: Did you say drill? When we asked you for more info it wasn't just for fucksies. If you have a highly inductive DC (an assumption here) motor driven directly by the BMS, the FETs may blow when you dump the inductive energy into them during turn-off. Interrupting inductive loads is not trivial unless there is some freewheel/clamp circuitry, which is why it would help to see the full circuit.As a quick solution/check you can add a freewheeling diode to the motor, assuming it's a DC motor, and try again.Your question is not really simple, and there are a lot of moving, non-trivial parts.

author: davisdesigns
author_rank: Contributor
timestamp: February 06, 2022, 07:48:46 pm
content: I was under the assumption that data sheets and photos is what people wanted.I'm converting my nickel metal hydride batteries to lithium for my power tools so drill impact driver Etc. I believe all the motors are BLDC.The BMS seems works fine under normal use unless I stalled the drill then either the FET's do their job and disconnect until I release the trigger for a second for it to reset or they they just blow up.I have a nice balance charger so I'm not concerned about the balancing part of the circuit all I care about is having the lipo pack automatically disconnect when it's under voltage or overcurrent to mitigate a fire.The packs I have are 124c so I don't think there's an issue with overcurrent other than possible short.FYI I'm not some hack fabricator that can't solder, at one point I designed and assembled circuit boards for about a decade. I just don't grasp the functionality of circuits but I have a basic understanding of what discrete components do.Just wondering if there's some way I can modify the BMS so that it is reliable or if I should just go in a different route. The only quality BMS I know of is Daly and they are far too expensive and too large for this project. And the voltage cut offs on Amazon are also too large and their relay is only 10 amps. I just find it hard to believe that there isn't some small low cost simple solution for this so many people are rebuilding their old battery packs and they just do it without a BMS