I made a clock with a mini weather station using a Arduino Nano, an DS3231 RTC, a DHT22 and displayed everything on a 20x4 LCD via an I2C interface. Everything worked perfectly when I was prototyping.
I then decided to make it permanent and moved it over to a Pro Mini, soldering everything to stripboard. When I was done, everything worked fine, except the DS3231 no longer kept time after a power loss. I double checked all my connections and obviously the code isn’t the problem.
The DS3231 has a battery cell in it, but it should be noted that I didn’t remove it while soldering and afterwards the open circuit voltage of the CR2032 was 3.6V, well above the normal spec. So, I replaced the cell with a new one and it still can’t keep time after a power loss.
The RTC keeps time without a problem when powered. So I’m wondering if I messed up the battery back up while soldering and if there’s no way to fix it.
I’m happy to post my code, if it would help.