DIY FM Receiver Power

I got a DIY bug and bought a small FM receiver off of Amazon.


Amazon.com: Icstation Digital FM Radio Wireless Receiver Module LCD Display DSP PLL 76.0MHz-108.0MHz: Home Audio & Theater


It's not much of a DIY project because really all it needs is an antenna soldered on and mounted in a case. It has a headphone jack and a USB jack. I thought it would be fun to mount it in an Altoid tin.


I have a question about it, though. I see that there is a place to solder DC power onto the board. If I plug USB power into the unit and measure the voltage on the DC IN terminals, it shows 4.5v DC. It made me think two things. First, if I solder a battery onto the board, what will happen to the battery if I plug the unit in to USB power? An alkaline battery might not like receiving 4.5v from the board. And second, if instead I soldered a rechargeable battery to the board, would it recharge when the board was plugged in? Would that be safe? Would the battery overcharge? Would there be some other circuit that I could add in to manage charging?


There is no 'off' button on the radio, so if it's going to run on battery power, I'll have to add a micro switch to turn the battery power off when not in use. I could turn the switch off and isolate the battery when using USB power, but it would be really slick to be able to charge the radio's battery like a cell phone.


I'm really a novice at this sort of thing, but I'm enjoying the learning coming along with it. If you have any thoughts, I'd certainly appreciate them.


Thanks so much,


Nathaniel
 
Modern rechargeable batteries are more fussy about charging arrangements than older technologies such as NiCd. You cannot simply connect a battery across a power supply. I suggest that for now you either use USB power, or a rechargeable battery which you remove for charging in a dedicated charger designed for that type of battery. You can add a switch to choose between these two power sources.

USB will normally supply +5V, so I don't know where you get 4.5V from.