Charging Li-Ion cells with (very) high currents generally decreases their life-expectancy, because they stay at a higher charging voltage for longer and the high voltage accelerates electrolyte decomposition (see above). On the other hand, charging with low currents is very time consuming. Thunder Sky recommend charging with 0.3C for an optimal balance between long life and short charging times. Charging with smaller currents will not harm the batteries and it will prolong their life.

Ideally the batteries should be recharged directly before use only, but this is almost impossible to achieve by solar charging. The batteries are very efficient (more than 90% energy efficient at currents below 0.3C) and are therefore very suitable for solar applications where life expectancy plays a minor role - for example the solar cycle challenge.