[moolight0551]

Has anyone had problems with the CR2032 battery in the RTC module? There are reports in the Arduino forum of the 3.6V batteries becoming 'fat' and the likely reason being that they are being charged with Vcc. The advice given is to cut a track to stop this from happening. More info can be found here.
http://forum.arduino.cc/index.php?topic=278270.0

Dave

[uncle_bob]

Hi Moonlight,
According to that forum thread you've linked to, it sounds like the jury is still out as they are measuring 4.2v after the diode.

Personally I haven't noticed my RTC battery going "fat"

Welcome to the forum btw.

[moolight0551]

Just thought I would raise the concern just in case it becomes an issue over time!

[hvalentim]

Not exactly the same. But this reminds me of the following story: I have an external temperature sensor which runs on a single CR2032 battery. The first time I installed it I fitted a CR2032 I purchased from a Chinese corner shop. It went flat after just one week. My conclusion was "heck, this thing sucks batteries like a mad fool, I am not going to replace batteries every week..." As a result I left it unused for more than one year.

One day I decided to give it another go. This time I fitted it with a CR2032 I purchased elsewhere in a established retail chain. It turns out it lasted for many months...

The moral: not all batteries are made the same. Some may be poorly manufactured or too old, others may even be second hand. Be particularly suspicious of batteries sold by the unit unpacked and make sure you are using quality batteries before concluding something may be wrong with the device using them.

My two cents which may or not help

[werk_ag]

Moonlight, your question is pertinent!
I'm convinced that the ZS-042 module was designed to be used with a LIR2032 rechargeable battery. Curiously all ZA-042 modules that I received in the past, come with a LIR2032 battery. Currently, due to restrictions in the shipment by air mail, sellers usually send the modules without any battery, and people start to put CR2032 batteries on it.

I think that, more easy and safe than modify the RTC pcb, is separately buy a LIR2032 battery.

[daveh]

The Arduino forum post referenced in post #1 above has had more replies since Werk_AG's response. One of the posts casts doubt on whether it is safe to use a LIR2032 with the ZS-042.

Has anyone here experienced problems using an LIR2032 and letting it charge on the ZS-042. Are people using the module with the charging circuit disabled?

[werk_ag]

I can just talk about my experience: I have some of those modules with LIR batteries running since at least 3 years. I never had any problem, and never noted any sign of the battery being warm.
For the obvious reasons I never used a CR2032 battery on these modules. They are designed to be used with LIR batteries, not just CR2032 batteries.

For those concerned about any possible risks, the easier solution is eliminate the charging circuit existing in the module by removing the diode and limiting resistor, and add a simple wire according to image bellow. Then you can safely use a CR2032 battery.