Will Li-Ion cells in a pack equalize?

One thing to remember is that all 18650 cells have internal PTC, so even if cell shorted internally, PTC would shut-down and it would become effectively open.

Regards, Yevgen

Trolling some websites (OK, Dell), I see 9 cells is a popular high capacity pack. I suppose it could contain 18 cells (i.e. paired), but I suspect not.

SoC

Charge state equalises simply because they are a voltage-mode cell (my term). If you don't believe me, try it.

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I have never seen laptops using 33v (3.7v x 9, if in series).

The most popular configurations on current laptops appear to be 10.8/11.1 volt stacks i.e. three cells in series ("three high"). On the Dells I have seen and/or own, they are offered as 6-cell standard capacity and 9-cell high capacity. In other words, three high by two wide (parallel) or three wide.

The key to these configurations is that they are NOT three separate 3-cell series strings commoned at the stack end terminals. The cells are linked (parallelled) at each intermediate node.

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Here's an obvious question. Assuming the notebooks have bridging batteries, why not just make a pack that looks like 3 3 cell packs. When one string is draining, fire up the next string. Should a cell fail, at least 2/3 of the pack will still work. I know people with Sony packs that haven't lasted longer than a year. Then again, why make a reliable product if you can sell more packs.

It is common business practice. Goods are intentionally projected to have certain average life, even if there is possibility to have it longer.

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Because it will be unnecessary complicated and the result would be no better than haviing parallel cells. Why don't you just carry a spare (some can have two separate batteries as well). It would just take a few seconds to swap them.

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This would be a better product since it would be more reliable. You could have a cell failure in each string and at least function. Further, assuming the bridge battery is still used, the electric swap hard is already there. Win, win, and win.

Some newer notebooks don't give you the option to swap batteries easily, especially the current generation Macs. Long gone as far as I can tell is the master power switch where the battery is completely disconnected.

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You would need load switches and/or relays in each string (size and cost). The rest of the world don't seem to agree with your ideas and concerns. With parallel cells, each cell is charging/discharging at lower rate and far better for battery life.

I am not familar with Macs, but I don't think Apple is dumb enough to stop people from changing batteries. If that's the case, one more reason to stay away from Apple.

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If you run alternate operating systems, some claim Macbooks are the way to go since there is far less variation in the hardware. Getting every function on a notebook to work under linux is difficult. On a desktop, you just pick the hardware known not to cause problems for linux, but for notebooks, you options are greatly reduced. You can't believe the hassles with soundcard and linux notebooks.