Chinese Battery Management Systems - Any Experience? - Page 1
Forum section: electronics / projects

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 29, 2016, 02:33:39 am
content: I currently am working on a few circuits that I need a stable 12V out, and ideally run on Li-Ion/LiPos.1 of them is for a project where I need a sort of a 'pocket-sized UPS' for a module, where it will kick into action in case of any power failure. Charge cycles isn't an issue as I will be using laptop 18650s (ie cheap) and replace them every year or so. It just has to be extremely portable & be shoved into a tiny (PCIE GPU sized) box.Another is for a set of portable 14" LCDs for my offsite filming work (again, likely 18650s or salvaged LiPos).Ideally, I would like to be able to just 'plug-n-play' any external 12-14V source to directly charge the batteries (and let the BMS handle all the overvoltage, undervoltage etc).I chanced upon these 3S BMS modules from evilBay:http://www.ebay.com.sg/itm/4A-5A-PCB-BMS-New-Protection-Board-for-3-Packs-18650-Li-ion-lithium-Battery-Cell-/141821040579http://www.ebay.com.sg/itm/4A-5A-PCB-BMS-Protection-Board-For-3-Packs-18650-Li-ion-lithium-Battery-Cell-3S-/291615617968I cannot, for the life of me, comprehend the chinglish being posted there.Does anyone have experience in using them?

author: station240
author_rank: Unknown
timestamp: January 29, 2016, 06:26:51 am
content: Looks a lot like a laptop BMS board.Connect 4 batteries in a string B+,B2,B3,B4,B- connect P+ and P- to the charger/device.I'd look for another ebay seller though, due to engrish and the "Item condition:New with tags"which proves they sell mostly clothing.

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 29, 2016, 07:15:04 am
content: Quote from: station240 on January 29, 2016, 06:26:51 amWait a min... Does this mean that I could just reuse the whole 6-pack (I meant the laptop battery pack, not beer :p) just like the Chinese BMSes? How do the multiple connections of the 6-pack work?

author: Fungus
author_rank: Super Contributor
timestamp: January 29, 2016, 10:17:10 am
content: Quote from: thejoggingmat on January 29, 2016, 02:33:39 amIf you're pulling laptop batteries apart you should find matching charger boards inside them. They usually take up to 19V (typical laptop supply).

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 29, 2016, 11:37:40 am
content: Quote from: Fungus on January 29, 2016, 10:17:10 amI have seen the boards and oddly they don't match those on Google (search). They are original Lenovo batteries, and all they have are sets of QFPN or BGA chips with no marking on them. One of them was even only comprising of one resin blob and a few of what appeared to be MOSFETs. Those I saw online which are well documented were from Dell or Asus (they only had the +/-, thermistor and ON pins).I've since discarded the boards. Still have 1 or 2 battery packs lying around from other Lenovo models though; maybe I will have another go.

author: Fungus
author_rank: Super Contributor
timestamp: January 29, 2016, 12:09:55 pm
content: Those ebay listings don't have input/output voltages.The output voltage is probably "whatever the batteries have" so you might end up adding a buck/boost converters to the output.They do tell you chip/part numbers though. Look up the datasheets and see what the chips can do.

author: amyk
author_rank: Super Contributor
timestamp: January 29, 2016, 12:18:11 pm
content: You still need a voltage and current-limited supply to charge, these are just protection boards that cut out on over/undervoltage and overcurrent. (I suppose you could just use current-limiting and rely on the board to cut off when it's full.)Quote from: Fungus on January 29, 2016, 10:17:10 amLaptop batteries are the same - no actual charging circuitry, that's inside the laptop itself. The batteries in laptops will have extra monitoring though, and one-time-failsafes that make them unsuitable for reuse.