Battery Life (simulation) questions

[ericohman]

What is it in a pedal that affect the lifetime of a battery?

If I have the schematic in LTSpice for example, how should I go to measure estimated battery life time?
Is it the total resistance that will affect the lifetime?

For example a Mr Springgy reverb pedal eats battery compared to a BYOC 2-knob bender fuzz. Must be some way to estimate the battery life if you have the schematic in a software like LTSpice.

[alanlan]

It's the current drain.  I don't know of the top of my head what the Amp/hour capacity is for a 9V PP3 style battery or what common effects use but it ranges from 100uA or so to perhaps 10's of mAs. 

So, to answer your question it's the static current drain when switched on which primarily determines battery life.  If you are simulating transistor level circuitry then you should be able to get a good idea from your simulation or calculate the drain as the sum of the drain of each stage in your circuit.  If you are using any op-amps, then the chances are that the simulator will not give you accurate figures and you should take the value from the datasheet.

Failing all of that you can measure it for real.

[Sir H C]

no need to be so complex.  Just put an ammeter on the battery terminals and measure current usage of the pedal (for some you have to actually play to get the real current).  Then based on the battery type you can calculate lifetime.  Every battery has a mA/h rating, so how many milliamps it can draw for one hour before it is depleted (IIRC).  So know the current usage, divide the mA/h rating and you get lifetime.

[brett]

Hi
a a general rule-of-thumb, high current pedals (esp. digital ones) consume 100mA (sometimes more!) and an alkaline PP3 9V battery (500 mAh) lasts 5 hours.
Low current pedals usually consume about 10mA (if they havean indicator LED, less if they don't) and battery life is 50 hours.
Obviously, others are in-between.
cheers