So, I had to google "Reserve Capacity".... It looks like that is how long a fully charged battery can run a 25A load before it drops below 10.5V. So, for a fresh battery, the Clarity should be able to operate a 5 Amp load (Accessory) for 5 * 85 = 425 minutes (~7 hours). OK, not forever... Use "Ready" if you want to be safe. And carry a jump pack to be double-safe (don't forget to charge it occasionally) !