As a part of an off-grid project I’m working on with, I need a low-power real-time clock (RTC) to periodically wake up my main circuit. I started working with a Z2-042 DS3231 RTC module (about 1 € from ebay), but quickly realized that out-of-the-box, it uses quite a lot of current for a low-power project. Luckily, some of the components on the board are not strictly needed. The easiest to remove are the power indicator LED and the battery-charging circuit, which can be disabled cutting the traces shown below:

Results:

(*: I did not write these down before cutting the LED trace, so these may be a bit off)

The test setup used a fresh CR2032 3V battery, and the “active current draw” is from when the DS3231 has the alarm interrupt on, and the SQW pin is used to drive a 1 mA to a transistor acting as a switch. VCC voltage was 5.0 V.

According to https://sites.google.com/site/wayneholder/low-power-techniques-for-arduino  you could also remove the resistor packs and the AT24C32D EEPROM on the bottom of the board, but these would require some desoldering. Reportedly, that could save another 0.5 mA on the current draw, totaling 0.1 mA in standby-mode. For the moment, I’m satisfied with the 0.6 mA. With AA batteries (e.g. 3 in series @ 2100mAh), I should be able to run the RTC module for up to 145 days, which is sufficient for the off-grid setup.