Do you use a 9V battery? Many projects use it as source energy. The nicad battery is good commonly used. We can recharge them when dies. If you do not have a battery charger. I recommend this is Simple nicad battery charger circuit.
It is suitable for beginners. But still works great. Charging batteries are commonly used in the circuit because it’s cheap. Because we use a simple little device really.
The Ni-cad battery charger circuit can be used with the battery will charge with 4.8 Volt current 800mA using it for about five hours, “which serves R1 limit the current flow.
To the Ni-cad battery charger circuit where the R2 and LED1 is told that the state of the battery charger that fully or to show that if LED1 on battery power is not full.
Simple 9-volts NiHM-Nicd battery charger circuit
Here is Simple 9-volts NiHM-Nicd battery charger circuit as Figure 2.
Input is 12-volts from normal DC adapter and take 9-volt battery to Snap connector.
Up to $20 shipping discount on first order now: https://jlcpcb.com/quote