[Ecky]

When I got home today I brought the lithium battery back inside. I'll let it thaw and examine its condition. Might just be frozen. It's been consistenty below 10F at night for the last few weeks.

After an hour I measured the parasitic draw with just the capacitors in the car: 25ma. There's probably optimistically ~1 amp hour of energy that can be lost before the capacitors will no longer have the voltage to start the car. This doesn't account for the trickle balancing circuit and natural self-discharge.

So, 40 hours to deplete the caps just keeping the clock and radio presets in the car. Or in other words, chances are good that if I park the car on a Friday and try to start it on a Monday, voltage will be a little too low to crank. The idea behind the lithium battery was to keep the caps topped up for 20-40x this long, but it looks like that just isn't going to happen in this weather. If I can't find a heater solution I'll probably snag one of the tiny 7Ah SLA batteries from work and run it until the weather warms back up.

EDIT: I wonder if the energy needed to keep the lithium battery warm and run the controller for this would reduce its standby time to less than that of the capacitors. I'll keep digging.