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18650 is not the amount of cells I salvaged but the reference of a common type of Lithium-ion battery cell, found in laptop batteries but also e-cigs, etc. It looks like a big cylindrical cell.
Photo of me testing the voltage of a cell (156KB)
Lithium is a precious resource so it interests me and friends at la Bidouille to find ways to reuse dead laptops batteries. In particular I brought a laptop that got killed by spilling coffee on it back in 2014 even though it was only a few months old — absolutely un-solarpunk, I know, but at least it's fun to disassemble it completely and research how to reuse its parts.
Even though 18650 is a standard format, there are a lot of subtle differences between the models. Because there is a community of enthusiasts salvaging those cells, there are platforms you can use to look up the cells references and obtain datasheets, such as on the website Second Life Storage:
Second Life Storage cell database
In the case of my dead laptop, the battery contained six Samsung ICR18650-26H cells (2600mAh):
ICR18650-26H thread on the Second Life Storage forum
For the fun I also looked at an e-cig cell: MXJO IMR 18650 (3000mAh).
Reusing unhealthy cells can be problematic or outright dangerous in the long term so you should be a bit cautious and not blindly reuse the cells you managed to gather.
Check the voltage with a multimeter. The flat end is minus, the ridged end is plus.
If the voltage is zero, the cell goes to the recycle bin. If you see people recommending to do a CID reset to repair it, be aware that it is circumventing a security mechanism and is highly dangerous, I do not recommend it!
Some measurements here, first for the laptop cells:
And for the e-cig cells after a full charge using the old e-cigs themselves:
If the battery was not used for a long time — mine has been left somewhere for 8 years — the voltage might have dropped a lot but that does not mean the cell is dead; you will need special care during the charging part. This is the case for my laptop cells above.
You need a way to charge the cells. A lot of references are floating around; if you think about getting a charger to test a few cells, try to get or borrow one that can also discharge the cells at a specific rate for later!
The datasheet of your cell will tell you the charging voltage to use. If any cell becomes hot while charging, it goes to the recycle bin.
Here is a bunch of references for chargers that I found some knowledgeable people used:
The IMAX is a popular choice because of its discharging capabilities, but the OPUS can work on four cells at the same time.
If your cell have a voltage that is too low to be charged with such chargers due to low voltage protections, i.e. below 2.5V or 3V depending on the model, you can try to slowly give it some power by connecting both ends to the corresponding ends of a healthy cell (or two AA LR6 batteries in series) until the voltage raises above the low voltage protection limit, then switch to the charger as usual. This should only take like half a minute.
You can also try to use a charging mode that does not have low voltage protection, e.g. NiMh mode, with a very low charging current (0.1A) but I never tried this.
Because you are charging cells that have not been used for a while, you need to use a charging current lower than specified, like 500mA instead of 1300mA. Dedicated chargers let you specify this current.
Photo of cells charging with the BT-C3100 (99KB)
Dysfunctional cells have a tendency to self-discharge, so a good test is to charge them fully to 4.2V, then leave them for 2 to 3 weeks and measure their voltage again.
If they are still above 4.1V, they are good. If they are between 4.0V and 4.1V, they have a slight self-discharging issue: it is not serious enough to discard them but it is something to keep in mind before using them. If they are below 4.0V, you will likely have issues with them in the long run and it's probably better to recycle them.
My cells before and after 16 days (2022-06-21 to 2022-07-07):
One of the MXJO cells seems to have some light self-discharging issues, but all the others are fine.
Devices with discharging capabilities will record the current produced by the cell so you know what to expect from it. Next are the results of the discharging test for the cells above:
My device is probably very optimistic as the nominal capacity of Samsung cells is supposed to be 2600mAh, but at least it's clear they are in good shape after
Photo of cells being discharged with the BT-C3100 (134KB)
Our hackerspace had to move out of our place and we've been without a neat place to undermine our electrical safety for some weeks now, so I'm publishing this note even though the cells have been resting in a box instead of being used for something. I would like to try salvaging laptop speakers to make a portable speaker using one of those cells, and maybe a solar lamp. Stay tuned!
