Replace CR2032 battery with 18650

[tingkeeyong]

Hi, I am looking to modify Xiaomi thermometer from using CR2032 into 18650 lithium ion battery. My major concern is, if 18650 voltage could be too high for the thermometer, especially 18650 can be 4.2V when fully charged. Can anyone advice if it's workable. Thanks.

[mikeselectricstuff]

Maybe add a 3.3v micropower LDO to be safe?

[NiHaoMike]

How about use a small LiFePO4 cell?

[mikeselectricstuff]

Or a pair of alkaline AA's..?

[Doctorandus_P]

Or just put a (few) diodes or an LED in series with the LiPo.
You do have to make sure the voltage drop is adequate over the whole power range (idle and sampling).

Voltage regulators always need a bit of current for themselves, and you have to look good at the specifications to verify the one you use does not need to much. Some go up to several milli amps.

LiPo's also need a good cutoff as protection agaist over discharging.

LiFePo may also be a good solution, It has a bit lower output voltage, but I think it's also more robust.

Yet another option is to use LIR2032. Same size as CR2032, but rechargeable.

Edit:
I had a click on that amazon link, and according to the description it already uses LiPo.
Do you get some commission for page visits on amazon or something like that?

[Labrat101]

What's wrong in using a Duracell CR 123a  series  3.2 volt, same voltage better specs