Hard to say how long a battery will last.
Nextion does not ship with a battery supplied by Itead
- so already your battery could be new or could be manufactured 7 years ago.
- such will effect how long it lasts.
The CR1220 battery is backup power for the RTC only.
This only is used when Nextion has no power to keep time while Nextion is off.
- so again, how long off and your battery is being consumed varies case to case
Considering the Battery is new, good manufacturer.
I want to know how often I need to change it, once in 6 months? once in a month? Once in a year?
By any chance you have any estimated timeline from previous testings?
How do you determine the battery is new?
Most sit for a year or two on a shelf before even entering distribution
- from distribution sits in a retail stock room until shelves are empty
So just because purchase is yesterday, does not make it new.
Many batteries can have a 10 year shelf life
- where within this 10 years period a consumer now acquires is hard to say
- but every month away from original manufacturing is already partial drain.
How much charge remains in your new battery is one factor.
I have seen RTC batteries last between 1 yr to well over 7 years.
- but all depends a lot on the actual battery
You're asking a question that has too many external factors to answer.
Biggest question becomes how much time is Nextion
unpowered with the RTC battery left inside.
When Nextion is being powered by its 5V supply and proper clean current
then the RTC chip is drawing power from the supplied supply - battery remains unused.
So in this unused state, the normal drain over time of the battery is a factor.
This really depends heavily on the specs of the battery manufacturing process
- specs for such will vary mfg to mfg with each having a given tolerance.
- one end of the tolerance spectrum is again different from the other end.
There is no means for me to tell if you purchased an "average" battery.
Average battery requires testing over 1300 of the same with mathematical statistical hoopla.
But no one will test 1300 to determine where their one sits on the scale.
And once drained in the test - an empty dead battery will say nothing
The replacement battery you then purchase ... well, test again? no.
Unfortunately, there is always this "penny pressure" when conceiving such products. I understand that it could not be done at the actual Nextion's price tag, but a rechargeable battery and a small IC as a charge controller, so that the battery is always recharged again when the main power comes in, would be a more comfortable solution. Moog Synthesizers from the 90 has this technology to maintain the whole bunch of settings and presets while the thing was powered off. Only now, 20 years later, I see the first of these batteries failing but they are easy to replace.
it is a "little" more than a few pennys ...
and many more little things people out of the process even never think about. But all must be payed ...
finally from the customer ...
I know... *sigh* ...that's why I wasn't requesting or even suggesting something, just writing down my thoughts...
Thanks for the info :)