# Battery life estimation

I have three AA 1,5V@2950mAh Alkaline batteries in series with a discharge rate of 3% per year. My circuit has a 3V3 LDO that will work until 3V6 is reached, so each battery will need to have at least 1V2.

In order to calculate the battery life for my circuit and check if it is able to last for 2 complete years I have the following conditions:

• The circuit consumes 380mA during 4 seconds 8 times a day.
• The circuit will then remain at low power mode with a consumption of 1uA.

I have done the following estimation:

• Operating duty cycle (per day) = 32 /86400 = 0.00037037
• Average current during operation = 380mA x 0.00037037 = 140.740 uA
• I consider Low power mode as 1uA 100% of the time
• Total average current = 141.740 uA
• Operating time = 2950 mAh / 0.141740 mA = 20812.64 h = 867.193 days
• Adding discharge rate I'd have --> 867.193 - 867.193 * 0.06 (2 years @ 3%) = 815.162 days

So it seems the batteries will be able to last for the twop required years.

Are these previous calculations correct? For sure I´m missing something...

• Looks correct to me! May 13, 2020 at 7:37
• Is the 3.3V regulators Iq less than that 1uA? equally is the leakage of the capacitors in your circuit less than that 1uA?, this stuff has caught me out so many times in the past. and as stupid as it sounds, keep silkscreen away from pads that could leak, contaminants build up along there ridges if cleaned poorly. May 13, 2020 at 12:47
• The LDO has a typical Iq of 2uA May 13, 2020 at 13:11