Bob, the beauty of that was that the switch was already there, I just swiped it from the useless CHUFF on/off function! 
With the two batteries in series, I have plenty of voltage for the couplers and smoke. It draws around .6 amps running light, and around .8 amps with a pretty heavy load on the drivers. I ran it on my DC bench supply at 19 volts and then put some real drag on the drivers, the current was up to around .8 amps. I figured in normal running, it would be more like .6-.7 amps. That's also with smoke active, so I think the battery life should easily make around three hours, not bad for $45 total for the batteries and charger. 
