A23 (GP 23AE) battery drain

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Pha5e

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I have designed a circuit consisting of Op-Amps. The circuit drain is a constant 30mA at 12V. I decided to use a GP 23AE battery (alarm key-fob type) which has a specified capacity of 55mAh.

However, I've noticed that the voltage drops below 9V after a few minutes and keeps dropping?

Surely the battery should maintain 12V for at least over an hour given the capacity?
 

No. Battery capacity is given at a certain current draw, which is usually quite low. The more current you draw, the lower the effective Ah is.

Plus, drawing 30mA continuously from something that small will definitely cause a rapid voltage drop. The cell is not powerful enough to provide that amount of current. The A23 is designed for short pulses of moderate current (like small ignition circuits or push-button transmitters) but not continuous high current draw.

Here is the spec sheet:

https://data.energizer.com/PDFs/a23.pdf

From the sheet: 55 mAh to 6.0 Volts (rated at 20K ohms at 21°C)

12V with a 20K ohm load is only 0.6mA!

Alkaline batteries have a steep voltage curve as they are used up (really, an increasing internal resistance dropping the voltage). It is inherent in their chemistry. NiCd or NiMH are better in this respect.
 
Last edited:


Thanks for your reply FoxyRick - I realised after posting that looking at the datasheet for the GP 23A, the 55mAh is quoted for a 20k ohm load:

**broken link removed**

They also have curves for a 470 ohm load in the datasheet which is more closer to the current drawn by my circuit. The voltage does indeed drop off quite steeply within 20-30 mins! I also realised reading the datasheet that the battery is designed for pulse applications and not continuous current draw!

I think I'll have to redesign my circuit to operate at a lower voltage!
 

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