4S2P LI ion battery pack arrangement, charging and BMS

Discussion in 'Power Electronics' started by adhith, Oct 8, 2017.

  1. adhith

    Thread Starter Member

    May 29, 2017
    46
    1
    hello friends
    I'm completely new to battery packs and I'm planning to make one of 4S2p configuration for my portable speaker project and i have some questions related to it.

    Qn. 1) I have bought 8 Li ion cells of 5800mAh each but I'm confused how to arrange the battery pack. 2 arrangements are shown in the pic and I heard that method 1 is good since its easy for balancing for the BMS, but will it be lacking anything when compared to method 2 in terms of total capacity or anything??

    Qn. 2) I have bought a BMS for the project (shown in the pic) which has balance protection in build, I guess P+, P- are connected to load, B+, B- to the end terminals of the battery. but I'm confused with its terminals B 1,B2,B3. from where should i number the cells ??

    Qn. 3) This is the problem that worries me a lot. I want to charge the pack with a 12v DC wall adapter, but I understand that the battery should be charged in CC mode and then CV mode. Since i use a 12V charger I'm suppose charge with 4.2 X 4 = 16.8 V with the help of a boost module. Unfortunately I can't find a CC, CV boost module instead could only find a CC, CV buck module. so I'm planning to first use a boost module with only CV mode to get the 16.8V or higher and then fed as the input for the CC, CV buck module to finally use it as the charging source for the batteries. MY question is would this arrangement works or not??

    Qn. 4) So if the above arrangement in Qn. 3 works then, what should be the charging current that should be set on the module??
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    8,133
    1,409
    The 4 cells go to B-, B1,B2,B3,B+ in series, the output is P- and P+ this is also your charger output which should be 16.8 to 17V, the bms pcb will automatically charge them in the correct way until fully charged, then stop, the load is connected to P+/-, when the charger is disconnected the batteries take over powering the load.
     
  3. adhith

    Thread Starter Member

    May 29, 2017
    46
    1
    Thank you very much Dodgydave for your support. Any suggestions for my remaining questions??
     
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    8,133
    1,409
    The charger usually is specifically designed for the lithium-ion cells, the algorithm is built in to charge it at CC at first, then switches over to CV, to top up the cells then shuts off.
     
  5. larry1024

    New Member

    Feb 23, 2018
    1
    0
    You might want to make sure you get a BALANCING BMS; not just a BMS that gives you over voltage and under voltage protection.
     
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