Hello, I try to powered the DS3231 by backup capacitator 5.5V 0,22F and i can say that is work very good. If I compare price of capacitator and LIR2031 the capacitator is 1/3 price. It can backup time module for 24h sure (tested). Now I try if it possible to backup it for all weekend. That is enough for me.
If you are wondering if I will ever get to the point (solution), here it is. The diode is in backwards. That is it. The diode's only function is to block charging of the CR2032 from power off of VCC, not provide a charging circuit. The resistor is a current limiting resistor intended to take the load off of the diode. The battery should provide power to VCC to keep the RTC running in case of a power failure. This is a one way job from the battery to VCC. The way the board is shipped from China, makes a power path from VCC to the battery, not the other way around.If you reverse the diode, you will have full functionality of the RTC, including battery backup. Only problem is that the power LED will drain the battery quickly. If you want to remove or cut anything, reverse the diode and then remove the LED so your battery will last longer when the system power is off. Remember, just because someone manufactured it, it does not make it correct. This board is both a bad design along with bad manufacturing. But does work if you fix it.
The correct solution is; (1000% SURE)Connect battery CR2032 directly to Vbat of DS3231, remove diode and/or resistor and problem is solved.Power consumption of DS3231 is very low so the time will run well for many years.
is 4.75 @ 20 ma bad for a non rechargeable battery?
Also the voltage is going to one pin on an ic when the main power is cut .. even before the diode stops it so I would venture to say the clock will keep its time from the battery when main power is out as it should.