Dear Professionals,
I have a RTC with backup battery switch function.
If the Vcc is remove, the RTC will switch to Vbat to power.
Now I have a choice to use a small 12mAH battery to be a backup battery.
So, I can calculate the theory work time of the RTC.
That is:
12mAH / 150nA = 80,000Hrs = 9.13 Years.
The Question is HOW CAN I TEST THE ACTUAL WORK TIME OF THE RTC ?
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Dear Professional,
Yes, your meaning is OK, but I think the situation is not so optimistic.
Because I think the battery will leak current when stay in air, or connect to the metal or something,
and I don't know the battery 's capacity if will be changed when supply 500nA, which is a small current.
Or I need check some parameter of battery ? Thank!
What type of battery? You need to find the self discharge characteristics of the battery. NiMH are not great so I doubt you will get 6 months. Lithium are far better but you need to check the specifications.
If you think about the problem thoroughly, you'll see, that part of the questions can be easily answered by measurements, others can't.
RTC current consumption of one exemplar - easy
Temperature dependence of the same - almost easy
Variation between lots - can be only answered by the manufacturer
Battery capacity at nominal current (e.g. 10 uA - 1 mA) - almost easy
Temperature dependence of the same - special equipment needed
Long term capacity and self discharge - nearly impossible to determine within acceptable periods
Temperature dependence of the same - even more complicated
Variation between lots - a matter of faith
In addition, I can report, that manufacturers sometimes feel a need to correct their long term performance assumptions...