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48V 13Ah vs. 48V 17.5Ah battery - same dimensions?

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  • Fred
    replied
    If you look at the specs it appears that both packs are a 13s5p config, The 2nd one says they are using 3.5Ah cells and while the 1st one doesn't explicitly say, they are likely using 2.5Ah cells (2.5 x 5 = 12.5) rounded up to 13Ah.

    Leave a comment:


  • Dshue
    replied
    A 13ah 13s5p with 2.6ah cells will have 65 cells total.
    a 15 ah 13s6p with 2.5ah cells will have 78 cells total.
    a 17.5ah 13s7p with 2.5ah cells will have 91 cells total.

    Using higher capacity cells requires fewer cells for the same total ah.
    Cell capacity in ah × the number of parallel cell groups = total ah.

    But like I said most battery builders use 1 case size. And they are typically large enough to house a 13s7p with 2.5ah cells.

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  • Dshue
    replied
    Most battery builders use a one size fits all case. A lower capacity pack will just have fewer cells or the same number of cells but lower capacity.

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  • 73Eldo
    replied
    A 48v pack has to have at least 13 cells just to get to 48v. This is the number you sometimes see listed like a 48v 4p13s. 13s means 13 cells (or groups) in series which gives you the voltage. A 52v has 14 in series. The P number is parallel so a 13s4p means there are 52 cells, 13 groups of 4 so 52 cells. 3p would be 39. 2p 26.

    So if you take that 13ah pack and guess that it was a 3p that would be 39 cells. Each cell then would be good for 0.33 ah each. If you wanted to use the same cells and go to a 4p that takes you up to 52 cells that would be more size and weight for the extra 13 cells but would give you 17.3 ah. The math doesn't quite work out that neatly but its close enough for this example. Notice how neatly the numbers fit there with may of the packs sold these days? This most likely means those cases have room for 52 cells but sometimes they only put 39 in.

    Lets say you just built the pack out of better higher capacity cells, maybe they are only .4 ah each. Back to 39 cells you would have a 15.6 ah pack that is the same size and weight as your 13ah pack is. If you could get 0.5ah cells 39 would get you 19.5ah. You go to a 4p with those cells you get a 26ah pack.

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  • MemberOfDistinction
    replied
    I believe that is plausible. The 13Ah pack simply may have less cells in it. You should be able to weigh them and easily see the difference in weight.

    If it were me, I would also go by the sellers feedback rating and comments.

    Leave a comment:


  • mudflinger
    started a topic 48V 13Ah vs. 48V 17.5Ah battery - same dimensions?

    48V 13Ah vs. 48V 17.5Ah battery - same dimensions?

    Hi all,

    I am a bit confused about two batteries and hoping somebody with more experience than myself could make a best guess...

    Basically, I currently have this 48V 13Ah battery running on my bike:

    https://www.ebay.co.uk/itm/154421583551

    The range is a tiny bit less than what I would like, so I am looking at buying this 48V 17.5Ah battery, which is the same brand as mine and appears to have the same case / dimensions and 4-pin connector:

    https://www.ebay.co.uk/itm/154127955561

    But a few things I am wondering...

    1. Is it plausible that two packs using the same case are getting different range? I was expecting the 17.5 to be larger.

    2. Do you think I can use the 17.5Ah battery with the mount on my bike atm (it's for the 13Ah battery but the connector looks the same)?

    Sorry if my question is a bit stupid but I've really confused myself and it's a lot of money to spend if it doesn't fit.

    Cheers!

    Jake

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