Cheap 18650s Tested

Posted by matt

Including shipping costs from Hong Kong, these li-ion cells cost little more than £1 each, so I really wasn't expecting much from them. They claim 3000mAh... I just hoped they might exceed 1000mAh. 

The first thing I noticed was how light they felt. Each cell weighed in at around 37g, whilst other XTAR cells I have were around 46g (note: the XTAR cells do have additional protection circuitry). I fully charged each cell with a XTAR MP1 charger, then run some discharge tests using 4.7 ohm resistors. The best cell lasted roughly 15 minutes longer than the worst, but that was only somewhere around the 70 minutes mark.
Not entirely happy with the above test, I recharged the cells and ran a more accurate test on a single cell (avoiding repeated switching between cells). This time I used a 2.4 ohm load giving a drain current of roughly 1.5A. The resulting discharge curve can be seen below and indicates the cell has a capacity of around 750mAh i.e. about 25% of the advertised capacity!
(Note: I twice disturbed the rig momentarily which resulted in the two ripples in the curve).
I am tempted to open the cells up to see what is inside: probably either a smaller cell or a reclaimed laptop cell. Check out this site for more extensive tests on 18650 cells: torchy the battery boy

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