Using battery with charge circuit attached

Hi,

I'm fairly new to using rechargeable batteries in my projects. Generally they are all powered by DC adapters or single use batteries.

In this project I'm making a Bluetooth speaker. I'll be using an Arduino to contol some basic functions such as lighting and wireless commands.

My question is how do I attach a battery charger to a battery and the rest of the circuit? Do I add a diode in front of the charger to stop any "backwards" current into the charger? Could that even happen? Similarly, can I power the circuit and charge the battery at the same time by hooking them up in parallel?

You cannot put a diode at charger's output (between the charger output and battery) as the charger must measure the battery voltage while charging. The diode will isolate the battery fully for such a measurement, moreover it creates a voltage drop by 0.7V.

You may charge the battery and use it to power the circuit basically, even it is not recommended by the vendors usually.

What kind of rechargeable batteries are you going to use??