Phoenix tall tubular tx 3500 contains 280 ah. It is mostly used with solar system for long backup. It is used in pairs as 2, 4, 8 or more with same sequence. This is the latest model of phoenix battery. They have introduced it in 2021 with up gradations in TX 3500 280 ah. It comes in power cube series. Tube technology is used in tall tubular series as there are less plates but height of tubes is better than normal lead acid batteries.Tx 3500 280 ah is a deep cycle battery. Deep cycle technology is best for solar system.