Lithium batteries remain healthier longer if a 50% or greater of its capacity is maintained on them. It doesn't hurt to keep it on the charger or recharge it after a small loss. The impact of discharging it more than 50% isn't that big of a deal though. It's not something you should worry about. By the time you could measure the difference, you may have a new battery or new PPC anyways.
JJB
