The Power Sonic PS-1290 12 Volt 9.0 Ah battery fits in most sailplanes. These batteries are commonly called "gel-cell" which is incorrect. They are Sealed Led Acid (SLA) batteries. They have been a standard in soaring which is slowly being replaced by the better performing K2 Energy Lithium Iron Phosphate batteries. The primary advantage to the PS-1290 over Lithium Iron Phosphate is lower cost. SLA batteries top performance will last up to a couple of gliding seasons.

Features
• Absorbent Glass Mat (AGM) technology for superior performance
• Valve regulated, spill proof construction allows safe operation in any position
• Power/volume ratio yielding unrivaled energy density
• Rugged impact resistant ABS case and cover (UL94-HB)
• Approved for transport by air. D.O.T., I.A.T.A., F.A.A. and C.A.B. certified
• U.L. recognized under file number MH 20845

Performance Specifications
Nominal Voltage: 12 volts (6 cells)
Nominal Capacity:
20-hr. (450mA to 10.50 volts) 9.00 AH
10-hr. (810mA to 10.50 volts) 8.10 AH
5-hr. (1.44A to 10.20 volts) 7.20 AH
1-hr. (5.4A to 9.00 volts) 5.40 AH
15-min. (14.4A to 9.00 volts) 3.60 AH

Original source:
https://wingsandwheels.com/aircraft-parts/batteries/power-sonic/power-sonic-ps-1290.html