I upgraded my T12FG with a Lithium Ion 2S2P 2800mAh battery from Robbe. This battery is equiped with a integrated balancer/limiter, which simplify the charge. This new battery should give 8:30 to 9 hours of working time which is more that needed.
I also decided to change my NC Manager 2 plus, a 20 years old charger from Simprop by a Robbe Quad EQ-BID 4x50W. This charger will allow me to charge simultaneously the transmitter and 3 planes. Convenient at the slope after a day of flight or competition to prepare the next day in a record time.