adding rechargeable battery circuit


I am trying to add a rechargeable battery circuit to my project. My project currently runs off of a cr2032 battery with about 200mAh. I see that the rechargable batteries have FAR less mAh so rather than using the rechargable 2032 with 50mAh I will probably use the rechargable 2450 which has 110mAh

In order to add a charging circuit can i just use the max1555 since i will most likely be charging through USB

also, can the circuit keep running as it is charging? my project runs on pretty low amperage anyway.

lastly, there batteries are rated for 3.6 volts, but does anyone know about what voltage they are when they are dead? I want to know so i can set the BOD on the tiny84 to the correct amount.

thank you guys!

To answer your first question, as long as your circuit uses less than the 280mA, your circuit will be able to operate while it is charging, but take note that the more milliamps your circuit draws, the longer it will take to charge the battery. For the second question, most lithium ion batteries should be allowed to discharge to about 3.3 volts. You can discharge them to 3.0 volts, but they will have a shorter lifetime. Also keep in mind that when lithium batteries are fully charged, they are at 4.1 - 4.3 volts, which could be a problem if your attiny84 is running on 3.3 volts.