Not exactly on the subject, but close enough.
I was curious about the voltage ripple on my DC supply with just a capacitor in place of the battery. It was already known to be very stable.
I borrowed an oscilloscope from work. There's no noticeable ripple, but a slight "splash" coincident with each ignition pulse.
The voltage is a bit high, and I suspect would be lower if I used a battery. Anyway, I'm happy with it.