# Rating battery for intermittent drain

Discussion in 'Electronic Design' started by Mike Stern, Mar 3, 2012.

1. ### Mike SternGuest

I am designing a compact signal generator to be powered by a 9V
alkaline battery. It consists of a transistor (not op amp) phase shift
oscillator and emitter follower. The output is a square or sinewave at
60Hz. Draws 12mA.

Given that the drain is not continuous, due to the waveform's duty
cycle, how do I estimate the total operating time in hours, assuming
the battery will provide 500mAH?

The circuit will function fine down to 6V, with corresponding loss in
amplitude.

Mike Stern

2. ### JamieGuest

If you use the math for power in alternating circuits you can get
In sine wave stuff, it would be P = IV*Cos(angle), you do a bunch of
samples and sum them up.

for a square wave, it would be 50% of what it would be when on, that is
is the square wave is 50% duty cycle.

Watts being a 1J/Sec, so I guess you can accumulate a second of that
times the duration of your test.

More on it later I am sure.

Jamie

3. ### Phil AllisonGuest

"Mike Stern"

** Completely irrelevant.

If your meter shows 12mA - that * IS * the battery drain.

From the data for the Energiser 522 that equates to about 45 hours.

BTW:

This kit from Altronics does what you describe and uses only 2mA from a 9V
battery.

Output level is constant with frequency and battery voltage down to 6V.

http://www.altronics.com.au/index.asp?area=item&id=K2544

Designed by me and published in EA magazine in 1996.

It will fit in a much smaller box than the one shown in the pic.

.... Phil

4. ### Phil AllisonGuest

"Jamie = Maynard A. Philbrook

** Maynard never has the right answer.

The know nothing code scribbler is never even close.

.... Phil

5. ### Mike SternGuest

True, true ...

Mike

6. ### misoGuest

Not to rant, but have you ever compared the capacity of a 9V battery
compared to 2AA cells and a boost? Basically I hate designs with 9V
batteries. AA cells are more cost effective. [In any country, you can
find chickens, AK47 ammo, and AA cells.]

Basically people snicker at designs that use 9V batteries these days. It
is not good engineering.

So is 12ma with no load?

7. ### JamieGuest

Phil, you surprise boy, I gave the correct answer. I gave him something
to work with. You on the other hand just want to blow smoke because you
most likely don't know how to break it down.

Doing power usage with loads of that type requires you to decompose
the time frame with the signals you are using and load levels they are
exerting. Those summed together can be used as an average energy use to
properly calculate the battery life.

Go blow smoke else where, I don't don't smoke and I don't like smokers
around me.

Jamie

8. ### Phil AllisonGuest

"Jamie = Maynard A. Philbrook

** It is a totally WRONG answer !!

** Battery drain is the AVERAGE current level being drawn - as read on any
standard amp meter.

You fuckwit septic twat.

..... Phil

9. ### Phil AllisonGuest

"Jamie = Maynard A. Philbrook

Fuckwit Pycho Radio Ham KA1LPA "
** Exactly what I wrote - you fuckwit, septic criminal shithead.

..... Phil

10. ### JamieGuest

So what you're saying is, you don't know how to calculate usage at the
circuit level?

That figures. any twat, as you say can put a usage meter on the line
for a reading. But maybe you have forgotten something? This is an
engineering area, not a fucking class room on how to use your amp meter.

Go back and play with your boom boxes.

Jamie