I carry 4 manual batteries with me at all times. I don't have a PCC (which I need), so I need as many bats as possible just in case. There's been times where I thought a new battery I put on was fully charged, only to have it die 3 puffs later. Then I freak out because I already used up two of my four batteries, and now I have to rely on the last one for another 4 hours until I can get the other 3 on a charger.
In other words. ALWAYS be overly prepared!
In other words. ALWAYS be overly prepared!