The PMS will work with any lithium polymer/ion chemistry in a 1sxP configuration, but the main concern is that current for fast charging is set in firmware (3A) which is a lot higher current than a single cell (18650 Li-ion) can generally handle. Currently, Gman has it it set to 3A, which is too high generally for a single cell application for portables. Everything changes depending on the specific cell specs, but as a general rule, lithium cells safely charge at 0.5C rates (read the maximum charge current rating in cell datasheets to be certain). The maximum fast charge current limits can be adjusted in firmware, specifically REG04 (ICHRG) for the BQ25895 by changing the first 7 bits to whatever you want the charge current to be. This requires a PICkit3 to re-program the uC though.