Bottom line is weight. A buddy of mine who gave me the engine ran his glow ignition system on 1 aa ! It's a learning curve for me so if I see a problem with that size setup then I'll go for the bigger size battery pack. Which by the way will probably be the case. Thank you for your reply. I was beginning to think it was a stupid question about adding a charge lead. I can build but the electronics is a weak point for me in this hobby. Thank goodness for RC sites like these. It helps take some of the mystery out of it!