12 Volt Dying Battery Simulator

[DavidM]

This is not meant as a criticism of anyone or anything, but rather a caveat.

Most "dying battery" simulators do not simulate a dying battery.  The dying battery effect would appear to be a product of a battery that is able to provide a short burst of current, but gives up easily in response to big transients.  The reduced voltage is only one parameter of what changes in the battery as it ages.  Truthfully, it is a more complex multi-dimensional phenomenon.  Dying battery simulators (and the Beavis Audio one is a perfect example of such) tend to provide a stable voltage and current, that mimics one aspect.

So, "starving" a circuit with such simulators can be musically useful and valid, and yield interesting and novel sounds, but the "dying battery effect" is a whole other thing.  This is not unlike the way that a phase-shifter or flanger or chorus can capture part of what a rotating speaker does, but leaves out a number of other equally or more important parameters.  In the case of weakened carbon-zinc batteries, it is the dynamic response to transients that simple simulation circuits do not capture.  To my mind, it would likely take a more intelligent input-dependent digital model to capture what weakened carbon-zinc batteries actually do.  Such things may well be out there, but I'm not familiar with any, myself.

Just a thought on this, One way it might be possible to add to the dying battery idea could be to use an op amp circuit in the signal path and rectify its output in the same way an autowah would do or a compressor does. This output could be used to control a variable resistance circuit which in turn can drop the voltage from the PSU/Batt on trasients in the signal.

This sounds quite doable and interesting. A half or full wave rectifier, a peak detector, maybe even attack and decay controls, an optocoupler (LED+LDR) and there you go...

[electrip]

What about

battery/big cap to ground --> constant current source (jfet) --> small cap to ground --> circuit load

electrip

[Palealien]

Here's a photo of the finished product.

(Should work this time - fingers X'd)