This small SMD charger control the current with a shunt resistor and terminate the charging cycle reading the voltage.
In order to change current/voltage parameters you have to modify the code, do not exceed 700mA.
The only limit of this imlementation is: once finished, it sinks 560uA of current through the voltage divider and ADC input
so leving the battery pack attached cause discharge in some weeks, this is unacceptable for good low self discharge products
like ENELOOP. The new model here!