# AA type battery drop

Discussion in 'General Electronics Chat' started by pazpaz, Sep 3, 2014.

1. ### pazpaz Thread Starter New Member

Nov 14, 2013
19
0
Hello all,

I am using 2 batteries of duracell of AA type in my circuit
ratings are 1.5v each with 1500mAh
circuit sleep current is 0.04mA
i want to calculate how much voltage drop will occur in a day.
please guide me how do I calculate per day voltage drop of battery is circuit is in sleep mode for 24hr

regards

2. ### crutschow Expert

Mar 14, 2008
12,988
3,226
The battery will operate for 1500mAh / .04mA = 37,500 hours or 1562 days until end of life. If you assume an end life voltage of 1V then the voltage drop per day is 0.5V / 1562 = 0.32 mV per day on average for a linear drop. In reality the initial drop per day when the battery is fresh will likely be somewhat less than that and the drop close to the end of life will be more.

3. ### MikeML AAC Fanatic!

Oct 2, 2009
5,450
1,066
You read it from the discharge curves provided by the battery vendor.

For example

4. ### pazpaz Thread Starter New Member

Nov 14, 2013
19
0
Hello,
thanks for reply. Can you tell me how you got 0.5V?
regards

5. ### Sidleg New Member

Aug 5, 2014
15
0
I'm not crutschow but I believe the 0.5V is due to 1.5V starting minus the 1V end life voltage, after which it is no longer useful.

6. ### GopherT AAC Fanatic!

Nov 23, 2012
5,989
3,734
Could you tell us WHY this is important? A daily voltage drop is not a consistent value on a battery. For example, if you have a high current draw for a short time, then let the battery 'recover', the electrochemical battery will have time for ion transport and diffusion of various reaction/oxidation reactions and soon show a higher voltage than right after the load was removed. Again, if you tell us what you are trying to do, maybe we could confirm you are on the right path or we could suggest an alternative path.

Cheers

7. ### #12 Expert

Nov 30, 2010
16,256
6,754
You have to stop trying to use a dead battery somewhere, so crutschow just made an educated guess (or looked on a chart somewhere) that you might choose, "end of useful life" to be 1.0 volts. You can choose a different voltage if it is appropriate to the circuit.

8. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
Here: http://data.energizer.com/PDFs/alkaline_appman.pdf
is an application reference for Energizer alkaline batteries, found on the link that MikeML kindly provided above.
I suggest that you read through it a few times; there's a good bit to digest.

9. ### MagicMatt Member

Sep 30, 2013
117
14
It's going to be affected by temperature etc. too - there's not a "per day" drop, because the drop isn't linear either... if anything, it's more of an S shape... initially drops quick, levels off for a bit, then starts to drop quickly again. Trying to look at a voltage drop per day just isn't useful, since it will also vary slightly between batches of batteries, actual capacity (which is never exactly what's on the packet - that's an average).