The listed lead storage battery are maintenance-free, sealed electrolyte batteries. They are relatively position-independent (should not be charged upside-down), deep-cycled, cycle-resistant and long-lasting (4 to 5 years). Charge voltage at an ambient temperature of +20°C: 12 V DC (6 x 2.3 V per cell) 13.8 volts, this can be subject to tolerances.