Hi dso,
received e-mail from BLF about your post, so here I am.
My new Ailis (luckily I received only one old version in six of them) all cut off charge at about 4.3 volt. This is no good for standard LiCoO2 Li-Ion battery, as they have no margins for excessive overcharge. A standard 1C 18650 will lose 40 percent of cycle life if charge is ended at 4.3 Volts. The charge/lifecycle curve is pretty steep for standard LiCoO2; at 4.6 Volts termination, battery is dead after 3 (three) charge/discharge cycles.
Matter is totally different when we are talking about more modern (and more expensive) hybrid cathode batteries. A 3450 mAh battery from Panasonic (according to its datasheet) has LiCoNiAlMn cathode and graphite anode. Newer releases (3900 mAh) from end of year 2015 will have a silicon anode.
Hybrid cathodes are more resilient, having a wider de-lithiation window, and less grow-shrink of the cathode (and anode) masses during charge-discharge cycle, so charging them at 4.3 Volts will cut maybe 15 percent off their lifecycle, which - at this point - I tend to disregard as a minor inconvenience.
If you use 18650 cells recovered from laptop batteries, which were all pure LiCoO2 chemistry, you will end up with shorter battery life in the new Aili.
My suggestion is to buy four Samsung 18650 - the 2600 mAh capacity, with a pink jacket colour - which are very commonplace with all Internet dealers and can be purchased relatively cheap, and are of hybrid chemistry. They keep in balance very well, and will not suffer too much from the 4.3 Volt termination. Set and forget it.
Hope this helps
Anthony