I want to know what battery you use. How long can it be used?

[Rittichai Youyaem]

Re: PCB design with nRF24L01 and Arduino Pro Mini

[nagelc]

I'm amazed what can be done with the basic low power instructions on the MySensors site. I have played with a few different types of batteries all in low power temperature nodes.
2 x Alkaline AA. I routinely get more than 2 years with arduino pro mini and dallas sensor.
LIFEPO4 AAA. This is a really weird battery. I got about 10 months out of it. Difficult size to find. i would stick with AA.
I have an LIFEPO4 AA powered node, but don't have good data on it. Over a year.
CR2032 coin cell. I get over a year using NRF5 and BME280.

The LIFEPO4 is nice for PIR nodes because they have very flat voltage curve around 3.2 to 3 volts. And rechargeable.

[NeverDie]

Eneregizer promotes their Lithium AAA and AA primary batteries as having a 20 year shelf life. So, depending on the use-case, you could get 20+ years out of them. The nominal math is simple: divide the average current draw into the rated amp-hour capacity of the batteries. That will give you the nominal number of hours they should last, and from there you can easily convert into days, months, years, decades, etc. With some batteries you may have to account for the rate of self discharge, as that may be higher than the current draw of your device.

Also, it's hard to find coincells that are rated for a shelf-life that's longer than 10 years. Duracell has some that they claim are rated for 10 years shelf life. A lot of others are rated for 5 years or less, and the cheap counterfeit ones from China last a lot less than that--maybe only a year. Unfortunately, a lot of what's sold on amazon seems to be counterfeit. It looks real, and the packaging looks real, but, at least in my experience, they're often counterfeit.

[nagelc]

I realize I hadn't paid that much attention to the rated shelf life of the batteries. More than a year on a battery seemed good enough. But now I need to shop around. Maybe a less cheap coin cell would actually be cheaper in the long run.
My Subaru remote key fob battery goes dead frustratingly often. I was blaming the fob, but maybe that is unfair. Going to buy a better quality coin cell next time.

[NeverDie]

@nagelc Yeah, that was me. I found it makes a difference.