Laptop Powered E-Bike

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    The whole reason I got into harvesting 18650s was to build an eBike without having to spend $500 on a lithium battery. I think I’ve got enough cells to get started. I’m learning as I go, so bare with me, LOL.

    I have a regular bicycle I’ll be converting. I’ll get a picture and some specs at some point.

    I’m considering a SmartPie5 from Here’s the specs:
    – Max phase current: 50A (not sure what this means)
    – Continuous Current: 18A
    – Open Voltage: 20V – 60V
    – Rated power: 200W – 400W

    Still learning to calculate what kind of battery to build. Especially since I’m using old laptop cells instead of new cells. But here’s what I have so far.

    The rated power, being between 200-400W means using a « 48V » battery, with a voltage range between 42-58.8V means I’ll come nowhere near the 18A limit, right? 18A would be for if I were using a battery as low as 20V to get the 400W power. So more Volts means less Amps, and that’s good for these old cells. If I’m right about all that, then assuming a lower limit of 3V per cell, the most Amps I should ever demand from the system is about 9.5A when the battery is at its lowest of 42V.

    A 14s battery will give me 58.8V maximum. If I want to keep the current at 0.5A per cell, I’ll need 18p. So that would work out to 252 cells, which should be plenty for the Watt-Hours needed for power and range.

    14s18p would be a pretty big battery, so I’m thinking of breaking it up into 6 7s6p batteries. Also, I’m thinking I’ll make the batteries longer and thinner by clustering parallel cells in groups of 2×6. I made a mock-up out of dead cells just to see how each battery would look:
    [Image: bc96eeec4e456ff45912d7fdc0c6e8dd.jpg]

    So 6 of these, 2s3p, would look like this:
    [Image: ceee0f8d74aef9c096c9ff2151a2de17.jpg]

    Seems like a lot of battery though. I wonder if I could get away with only 4 of these. That would require 0.8A per cell. That would save me 84 cells and 1/3 of the weight and space. And it would make charging much easier.

    I’m thinking if I want to add lights, I’ll put together a little 12V battery. Most things run on 12V nowadays.

    Not sure what to do about charging.
    Please help.

    I didn’t find the right solution from the Internet.


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