As Matt posted and I believe was in a "Soaring" article, LiFePO4 is a much better technology than the old LiPo or LiIon. There are videos of people trying to blow up LiFePO4 cells or saw them up on YouTube. They didn't make the Darwin Awards.
Each 12.8V battery pack that looks like your old 8AH SLA battery has a charge/discharge controller on board. Weighs 50% of the equivalent SLA battery.
Tenergy or K2 are available in the USA directly or from their resellers, mine from all-battery.com.
Airbatt is available in Europe from accu-24.de. One section of their online catalog lists them by sailplane model.
Jim