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  • Ignatus Friday, January 13, 2017 11:41 PM Reply

    Could somebody please shine some light on this?


    I already bought this module and finally want to use it for a 4S3P Lipo pack.

    Each cell in my pack is a LG (LGABF1L1865) with a 3300mah capacity = 39,6Ah total.

    The connected load (Laptop) is max just 3Amps.


    So, according to my limited knowledge this Buck/Boost module is already totally overkill/ very generously specced for my project.


    However the tech spec of this item Quote:

    " 2. Inputs with 15A fuse" - makes me wonder what the manufacturer is trying say.


    ..and yes, that 15Amp fuse sits just behind the DC Input on the PCB.



    Thanks,

    Ignatus


    Edit: I wrongly stated the cells brand as Panasonic, but I'm using 12X LGABF1L1865 (possibly will upgrade to 24 cells) 4S6P.

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    post edited by Ignatus on 1/14/2017 at 7:24 PM
  • desolder Top 10 Forum Poster Saturday, January 14, 2017 10:02 AM Reply

    Your total capacity is not 39,6Ah. You only have 3 cells in parallel, so capacity is 9,9Ah. You have 4 cells in series, so the voltage is nominally 14,4V.


    The 15A fuse is not meant to imply that it can sustain 15A of input current forever. Regardless, this should be sufficient your laptop. You didn't specify what voltage your laptop uses. Assumig it's 20V at 3A, then it takes a maximum of 60 watts. Converting that from 12V requires 5A minimum. Then assume 80% efficiency and that means it will pull 6A at 12V. It's better to be a little overkill than running right at the edge of it's limit.


    output short circuit is not afraid


    Well that's good to know. I hate it when my output shorts are afraid. LOL

    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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  • Ignatus Saturday, January 14, 2017 5:22 PM Reply

    @desolder


    Thanks a ton for your help!


    I am now more certain than ever, that I should just not try to make any calculations at 3am :)


    So, it is 39,[email protected] nominal voltage and my pack is nominal 14.8V @ 9,9Ah.


    The laptop requires 14.75V and has a max consumption of 3A = 45Wh if the CPU runs at full load, with full Display brightness, fan etc...


    So, if the pack is fully charged this module works as a buck module converting from 16.8V to 14.75 and gradually / once the voltage of the pack sacks, it starts to boost it to 14.75V.



    Quote: "The 15A fuse is not meant to imply that it can sustain 15A of input current forever."



    For the sake of brain excercise, let us assume I'd like to double my battery pack to 4s6P with an approx 20Ah [email protected] nominal voltage.


    The 15Amp input fuse mentioned will then blow out?


    -Or am I right to assume that the fuse rating is only relevant in conjunction with the whole process of boosting to a required output voltage/ the connected load, as explained by you in the example above?


    In other words: I could connect to this buck/boost converter a 160Ah Truck battery as long  no load connected without blowing out that fuse?



    Kind regards.

    Ignatus



    "output short circuit is not afraid"


    I'm afraid I'm not going to like the smell of burned skin on my fingers from all the sparks.



    Edit: Deleted large blank space at end of this post and reformulated/ addded a "truck battery" example to my last question.

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    post edited by Ignatus on 1/14/2017 at 5:36 PM
  • Ignatus Saturday, January 14, 2017 8:21 PM Reply

    @desolder


    I havent' figured out how to send you a PM. - I wish it was as easy as clicking on your username.


    I know you said tips are not needed, but it's the least that I can do, apart from being greatful for your help.


    Now I just want to make sure that you receive them when I send them. I've sent you the first 50 something points a few weeks ago with help of MayeTao.

    In future I'll wait till I have at least 100 points together before asking somebody from DX to make a manual transfer to you.. which should be pretty soon I think I got about 70 points from my last order and I'll have to write a few more reviews ;)


    Thank you so much for helping me and others on Dx. You and the other "oldtimers" here make Dx / this forum really great!


    Sincerely,

    Ignatus




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  • desolder Top 10 Forum Poster Monday, January 16, 2017 7:29 AM Reply

    In other words: I could connect to this buck/boost converter a 160Ah Truck battery as long  no load connected without blowing out that fuse?


    This is correct. Amps and Amp*hours are not the same. Using the water analogy, amps is like gallons per hour, and  amp*hours is like gallons. A larger capacity battery (of the same voltage) will not push more current through the circuit.


    The water analogy breaks down a bit when considering packs which are rearranged from the same number of cells. In your example you have 12 cells of 3300mAh each. When arranged into a 1S12P pack, you will have a battery with a voltage of 3.6 volts and a capacity of 39.6 amp*hours. When arranged as a 4S3P pack, the battery will have a voltage of 14.4 volts and a capacity of 9.9 amp*hours.


    With no load, the converter will draw very little current, maybe a few tens or hundreds of milliamps.

    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

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    post edited by desolder on 1/16/2017 at 7:30 AM
  • Ignatus Monday, January 16, 2017 8:04 AM Reply

    Thank you for all your patience, Desolder!


    All clear now.


    Pictures will of the build will come soon.



    Kind regards,

    Ignatus

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  • Maye_Tao Wednesday, January 18, 2017 1:49 PM Reply

    Thanks. @desolder

    One tip for you.

    Be happy. ( *^_^* )
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  • desolder Top 10 Forum Poster Thursday, January 19, 2017 1:08 AM Reply

    Thanks Maye_Tao!

    What's up with the scrubbed LED driver IC markings?
    What are they trying to hide?

    Posts(7073) | Reviews | Tip post

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