1
\$\begingroup\$

This question already has an answer here:

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.

\$\endgroup\$

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

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • 1
    \$\begingroup\$ @ 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). \$\endgroup\$ – analogsystemsrf Aug 25 '18 at 16:17
  • \$\begingroup\$ Yes, thanks. But this would give me time to discharge. I need to compute "time to 1.1 volts"... \$\endgroup\$ – Fabio Marzocca Aug 26 '18 at 9:30
2
\$\begingroup\$

Average current is given by

$$ I_{AVG} = \frac {80m \times 8}{30 \times 60} = 0.35 \ \text {mA} $$

enter image description here

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.

\$\endgroup\$
  • \$\begingroup\$ Can you pls explain the formula? What is the "6" at the numerator? What is 60x30 at the denominator? \$\endgroup\$ – Fabio Marzocca Aug 25 '18 at 11:33
  • 1
    \$\begingroup\$ My error, I'm afraid. It should have been the 8 seconds on time. Fixed. \$\endgroup\$ – Transistor Aug 25 '18 at 11:38
  • \$\begingroup\$ Ok, thanks. If the average current is 0.35mA I should expect a lot more than 500 hours. Isn't it? \$\endgroup\$ – Fabio Marzocca Aug 25 '18 at 11:39
  • \$\begingroup\$ Correct, but there are no figures published. There's a Battery University site that may have some figures. Do a search. \$\endgroup\$ – Transistor Aug 25 '18 at 11:40

Not the answer you're looking for? Browse other questions tagged or ask your own question.