PowerSource 01-356 WP20-12I Battery Power Source batteries feature sealed construction to allow safe operation in any position; a specialized oxygen cycle recombines gases during overcharge so there is no need to add electrolyte, and they are factory pre-charged Special separators, advanced deep cycle plate composition, and a carefully balanced electrolyte system have greatly improved the capability of recovering from deep discharge, up to 800 cycles Power Source batteries may be used in series and/or parallel to provide a choice between voltage and capacity; the same battery may be used in either cyclic or standby applications without sacrificing life or performance High-impact resistant ABS non-conductive plastic, styrene, or polypropylene make up the durable case and provides excellent resistance to vibrations, shock, chemicals, and temperature Replacement for BMW 51913