NiCd batteries are very useful late days as they are with same dimensions as ordinary batteries. 
From time to time they have to be pulled out of the device and re-charged. (Time of discharging depends on the current consumed.) 
The battery have to be charged during a fixed period of time with a fixed current, which is about 1/10 of battery capacity (as an example, NiCd battery wit a capacity of 900 mAh should be charged for 14 hrs with 90 mA). 
Input voltage depends on the number of batteries charged (connected serially): 
- for 2 batteries - minimum input voltage 5 Volts. 
- for 4 batteries - minimum input voltage 7,5 Volts. 
- for 6 batteries - minimum input voltage 10 Volts. 
Overall dimensions PCB 32x23mm. 

This product is a DIY assembly kit.