KX2's internal battery capacity when charged from different voltage sources - and a new product for the KX2

The manual for the KX2's internal battery charger (KXIBC2) allows for a variety of input voltages, up to a maximum of 15V, to be used to charge the radio's 2.6AH lithium battery. The manual also mentions that lower voltages (down to 11V) can also be used although the battery will not be fully charged at these voltages.I was curious to see how a lower charging voltage - ie, a partial charge -