# Calculate battery duration [duplicate]

Maybe this is a trivial question, but I am struggling with it for a while.

I have an alkaline AA battery which is consuming 80mA for 8 seconds each 30 minutes. I need to calculate how many days it will last before reaching 1.1v. I know it depends a lot on the battery type, but let's say it is a Duracell battery.

I have problems in calculating the "average" consumption per hour, as the battery is drained for just 8 seconds (80mA) each 30 minutes.

Thanks for any help.

## marked as duplicate by Marcus Müller, Andy aka, Leon Heller, winny, MapleAug 26 '18 at 3:59

• @ Fabio This is an energy question. Compute the energy consumed each hour. (ampseconds). And examine the typical amphours of your chosen battery size (e.g 1 amp*hour). – analogsystemsrf Aug 25 '18 at 16:17
• Yes, thanks. But this would give me time to discharge. I need to compute "time to 1.1 volts"... – Fabio Marzocca Aug 26 '18 at 9:30

Average current is given by

$$I_{AVG} = \frac {80m \times 8}{30 \times 60} = 0.35 \ \text {mA}$$ Figure 1. The Duracell AA Plus Power quotes for currents down to 5 mA continuous.

This shows that at 5 mA you can expect > 500 hours. You'll have to extrapolate for your load conditions.

• Can you pls explain the formula? What is the "6" at the numerator? What is 60x30 at the denominator? – Fabio Marzocca Aug 25 '18 at 11:33
• My error, I'm afraid. It should have been the 8 seconds on time. Fixed. – Transistor Aug 25 '18 at 11:38
• Ok, thanks. If the average current is 0.35mA I should expect a lot more than 500 hours. Isn't it? – Fabio Marzocca Aug 25 '18 at 11:39
• Correct, but there are no figures published. There's a Battery University site that may have some figures. Do a search. – Transistor Aug 25 '18 at 11:40