Just a public service announcement for any newbies, as I nearly fell into this trap (well actually did fall into the trap but then quickly realized what happened.) I know this has been covered on the forums before but thought I would provide an update.
Recently ordered a DS3231 RTC module and got a very nice looking board from “diymore.cc” via Amazon. Came with the better DS3231SN chip, soldering looked decent, etc.
But it still has the trickle charge circuitry on the board. See photo - with a 5v supply to Vcc on the DS3231 module, I measured 4.8v on the Vbatt terminal.
So if your application calls for using a CR2032 coin battery for backup power, as mine does, you will need to mod the board or use an alternative to the 2032.
There are lots of resources out there on how to do the mod so I won’t go into that here.
Yes, the expensive LIR2032 can be used as it is rechargeable.
4.8 plus volts does seem rather high though since there is usually a 1n4148 diode (and resistor) in series with the power source.
Anyway, the reality is that many people use these modules at 5volt and want only a cheap 2032 cell, so should understand the consequences of doing so, and the required modifications.
I am running my DS3231 from 3.3v (Arduino Zero). I measure just under 3 volts at the battery with the battery removed. Probably no concern in this case.
