Powersonic Psh12180Fr 12 Volt 21Amp/Hr Batt Sealed/Maintenance-Free - The valve regulated, spill-proof construction allows troublefree, safe operation in any position. There is no need to add electrolyte, as gases generated during overcharge are recombined in a unique Valve Regulated Design - Our batteries incorporate a series of one-way low pressure valves. These self sealing valves allow the venting of any excess gasses that may be produced in the battery due to severe overcharging. Design Flexibility - Batteries may be used in series and/or parallel to obtain choice of voltage and capacity. Due to recent design breakthroughs, the same battery may be used in either cyclic or standby applications. Rugged Construction - The high impact resistant battery case is made of nonconductive ABS plastic to UL94-HB. This material imparts very good resistance to shock, vibration, chemicals and heat. Certain models feature flame retardant (FR) cases. Wide Operating Temperature Range - Power-Sonic batteries may be discharged over a temperature range of -40C to +60C (-40F to +140F) and charged at temperatures ranging from -40C to +50C (-40F to +122F)