The BLN-1 replacement batteries came with a "DSTE" branded travel charger. I have read about the shoddy design of chargers and low power devices coming out of China and decided that it might be best to take the charger apart to see what makes it tick.
Photos of batteries and charger.
The MC34063 is a common switching boost/buck regulator.
We also see a full-wave rectifier on board and what appears to be a step down transformer.
Charger open voltage is 8.403V. This should represent the CV stage. The question is if the CC stage will allow the voltage to any higher than 8.4V.
For the record, Li-Ion cells have a variety of terminal voltages depending on the chemistry. Standard cells, however, are typically maxing out at 4.2V per cell. For a 2S cell, this would be 8.4V.
Battery innards reveal that the capacity is actually 1020mAh and not 1450mAh as claimed. They also do not look like Sanyo batteries. A 10k resistor is soldered from the "T" tab to ground but does not fool the original charger.