Tips for identifying battery packs with high capacity cells

If you are interested in finding laptop battery packs with high capacity cells on ebay, it helps to know that government regulations require that battery packs with more than 100wH of capacity need to be transported as hazardous materials. Needless to say, no manufacturer sells battery packs with more than 100wH capacity.

The 100wH limit places an upper bound on the number of cells in a pack, and their overall capacity.

In the past, companies sold 12 cell packs. Those packs might seem like a great source of cells, but keep in mind that the cells won’t have more than ~2,300 mAh nameplate capacity. Actual capacity could be even lower, because 12 cell packs are probably more than 5 years old.

Improved energy densities mean that extended packs are now more likely to have 9 cells. A 9 cell pack at the 100Wh limit will have cells with ~3,000-3,100mAh capacity.

If you want cells with more than 3,000 to 3,100 mAh capacity, you’ll have to look at 8 or 6 cell packs. The best cells 18650 available today have a capacity of 3,200-3,400mAh. An 8 cell pack with such cells would be in the 95-100wH range. A 6 cell pack with such cells would come in at ~75wH.

I haven’t come across any packs in this range, but I’m also focusing my attention on packs that work out to $2-3/cell, which pretty much rules out anything using the latest and greatest cell technology.

So, bottom line, if you are looking for 3,000 mAh cells, you need to confine your search to packs with 9 cells or fewer. If you are looking for 3,200-3,400 mAh cells, you’ll need to narrow your search further to packs with 8 cells or fewer. Happy hunting!

4 thoughts on “Tips for identifying battery packs with high capacity cells”

  1. Thanks for the comment, Ellen.

    My interest is in finding inexpensive original laptop battery packs as a source of inexpensive, high-capacity cells for other uses, like flashlights or power banks.

    It is interesting that you don’t have good experience using high-cap cells to refill a laptop battery. What sorts of problems did you encounter?

  2. hi,dear. if you want recell a battery,donot use high capacity cells to do it. such as 3400mah cells
    i now write here in Chinese” 用高容量电池换芯是以 电池使用寿命短为代价的, 换芯完后,电池容量在使用一段时间后掉电很严重,也就是很容易充满,但是使用时间短,根本就达不到电芯标称的容量” i do not know how to express it in to English,but i just say it is our experience,we had done battery recell refill business since 2006, we donot use 3400 mach cells to recell refill battery,because it seems that these cells works good on flashlights and powerbanks which do not have special demand on cells,the protective board of flashilight and powerbanks also are not so complicated as laptop battery, but 3400mah cells works not good on laptop battery. i just say it is experience. these cells ‘ disadvantage will appear after half a year if you recell by it.

  3. Thanks, Ellen.

    What disadvantages do you see, do the protection circuits die?

    From my understanding, I can see understand why one wouldn’t want to use high-capacity cells in a recell.

    For one thing, they usually need to be charged to a higher voltage and/or discharged to a lower voltage to get the full capacity. If treated like a typical cell, you’ll only get 80-90% of the nominal capacity. The protection circuits of laptop packs designed for lower capacity cells will probably create problems, even if the management chip can be reconfigured.

    I am going to use custom circuits for my custom battery packs that can be configured for a variety of cell types.

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