What is the difference between using internal AA batteries and an external lead-acid battery for the transmitter?
When running on 4 AA batteries, the transmitter will transmit at a somewhat lower power to conserve power, and it will still be good for > 60′ of transmission. A fresh set of batteries will last for 1-3 days of racing. When running on an external lead-acid battery, the power is increased and even a small motorcycle battery will power the transmitter for many days.