Li-ion BMS and Battery pack shrink wrap - Page 1
Forum section: electronics / projects

author: dmxlights
author_rank: Newbie
timestamp: June 27, 2020, 09:56:17 pm
content: Hi,I have 2 questions and i am sorry if they have been asked before.1 has anyone used the Li-ion BMS from ebay like this onehttps://www.ebay.co.uk/itm/BMS-PCM-Circuit-Li-ion-Lithium-Battery-3S-10A-18650-Charger-Protection-Board/383573816394?hash=item594ec7f44a:g:cb0AAOSwiXpe13Yqif so are they any good for charging the battery pack and cutting out when reach the low point of li-ion pack. I seem to have read mixed reviews on them.Shrink wrap for battery packs what is the best to get and also how to measure it as in size for battery packs.

author: tunk
author_rank: Super Contributor
timestamp: June 27, 2020, 10:21:44 pm
content: I think they're only for protection, not charging, i.e. you have to provide the CC-CV-cutoff charging yourself.

author: ocset
author_rank: Super Contributor
timestamp: June 28, 2020, 11:42:50 am
content: i just looked for the datasheet for the board but couldnt find it. There must be a datasheet to show you where the charger power source will be connected.By the looks of it, there are not "Power" componments on the PCB, so i guess its just checking the voltage on each cell and not doing any balancing.But that can be fine if the cells are well matched, and even if they are not matched, it might just mean you only get up to 80% of full charge, which might still be ok?But please post datasheet if you find it...then we can assess it.

author: dmxlights
author_rank: Newbie
timestamp: June 28, 2020, 12:40:26 pm
content: Thank you to all who comment.I have got one of the board from a friend and the main chip is a 8254aa which from a quick google can be used up to 4 cells.As I have said I have got mixed reviews on them and if anyone here as used them or know other boards I will using 3 cells.I am also aware that I am going to need a power supply that is cv/cc which I can use my bench power supply for testing. I will be using the packs I build for special that I have build or will build that will be used on stage. Well this is the main plan but I know I will use some of the packs for something else as well.I would be like to plug in a cv/cc power supply and charge them without having to take or use my rc battery charger which can do more cell and I know would be better.

author: wizard69
author_rank: Super Contributor
timestamp: June 29, 2020, 06:10:03 am
content: Never used the board.In some ways I was surprised that the vendor added as much info as they did but at the same time disappointed with what was left out. The missing info includes a lack of a link to a manual or data sheet, no reply's or comment section.I'm not sure if this store is related to the original manufacture or a fly by night operation. Not knowing my way around the marks in China is why I often buy stuff like this locally. Yes a huge mark up but I'm more likely to get my questions answered.

author: abyrvalg
author_rank: Frequent Contributor
timestamp: July 01, 2020, 06:15:03 am
content: This is a “standard Chinese BMS” without balancing and one combined port for both charging and discharging. It does the things described in 8254A datasheet - overcurrent and per cell overvoltage/undervoltage protection. It can terminate the charging on it’s own (as overvoltage protection), but this will be harsh to the cells - high current at the end of charging is bad. Also the OV threshold can be pretty high above the normal Vmax of the cells (look at full 8254Axx marking on the board and consult the settings table in datasheet for actual OV/UV/OC values). So a CC/CV charger is needed.The quality depends on 8254A IC source - in worst case it can be a factory reject with thresholds far from stated in the datasheet, doing no real protection.

author: m3vuv
author_rank: Super Contributor
timestamp: July 01, 2020, 07:35:11 pm
content: ive tried a few chinky bms boards from china,most are crap! great if you want to kill yor batterys in a jiffy,steer clear!

author: dmxlights
author_rank: Newbie
timestamp: July 01, 2020, 10:52:11 pm
content: Thank you all who have replied.Ok I am not going to use them and on another note does anyone know of any good BMS that I can get for a 3S pack.I would like to be able to charge the battery(s) pack from a 12.6-13v cv/cc power supply and also cut out when the battery get low as in discharged.I could also every so often charge them on my good RC battery charger which does balance charging.