DaveJfr0 posted:Other than consuming less power out of the capacitors (and lasting longer), I don't see how lowering the input voltage to the decoder from the keepalive will change its behavior as the processor should remain on, maintaining constant speed to the motors, powering the sound, lights etc.
From my original post:
The output of the converter is tied to the high (track) voltage bus U+ on the decoder. The capacitor on the converter output is important because the high voltage bus on the decoder actually fluctuates quite widely. Without a capacitor on the output of the converter, anytime the bus voltage drops below the converter output, it draws energy from the supercap to maintain it, and the supercap will never charge.
and:
I set the boost converter output to 12.5V. This number is important, and somewhat layout-dependent, since the high voltage bus on the decoder depends on your track voltage. Too low, and you will have a noticeable drop in speed when the keepalive kicks in. The ESU Powerpack actually exhibits this. Too high, and the supercap will never charge, because the converter will be intermittently supplying power to the high voltage bus. Testing on my layout showed the 12.5V provided nearly seamless transitions from track power to supercap, and charged reliably.
So it may be fine at 15V DCC voltage (I think it probably will). But, it may also be that the decoder bus voltage drops below the regulator output voltage occasionally, which will be more likely with a lower track voltage.
