I have a rechargeable battery pack 4*AA of 1.2V NiMh type, which when measured fully charged (individually by a smart amp regulated charger) and without load shows some 6V. The load will be a PIC microcontroller drawing almost nothing almost all day long except for some 5-10 minutes few times a day activating a 5V relay. To not change batteries too often I am considering to connect a 5V switching power supply from an old phone charger. It shows 5V both without and with load. Charger would only supply power and charge batteries when the relay is activated, thus hopefully prolonging battery life and not drawing unnecessary load when nothing needs it.
First worry is to not fry the chip, which can tolerate up to 5.8V, but the batteries giving out 6V.
- Is that safe enough to just go with it and instead not have the batteries charged so high - charge them with say the stable 5V from the phone charger?
- Will the batteries tolerate such below nominal charging setup continuously or get damaged or charged over the 5V up to the 6V?
- Do I need to lower the voltage down to 5V from batteries to chip with some diode?