Ammeter to Voltmeter...who does it?

I just had a thought probably a stupid one. But on your IVR schematic why should the capacitor be rated 15v or more in a 12 volt system, that when operating at a charge is around 14 volts?
Things that make you go hmmm.
Volt rating of the capasitor could be a billion. Any value above 12 volts works.