2.2.5 Backup Battery ConnectionThe backup batteries and Back-up Battery Cable provide a backup power supply to allow full use of the PBXin the event of a power failure. In case of power failure, the backup batteries automatically maintain the powerto the PBX without interruption.User-supplied Items• Backup Batteries: VRLA (Valve Regulated Lead Acid) 12 V DC ´ 3• Back-up Battery Cable: KX-A228WARNING• There is a danger of explosion if backup batteries are incorrectly replaced. Replace only withthe same or equivalent type recommended by the battery manufacturer. Dispose of usedbatteries according to the manufacturer’s instructions.• Make sure that you do not short the backup batteries or cables.CAUTION• Make sure that the Back-up Battery Cable is securely fastened to both the backup batteries and thePBX.• Make sure that the polarities of the backup batteries and wiring are correct.• Use the correct type of Back-up Battery Cable for the PSU.NoticeBe sure to comply with applicable local regulations (e.g., laws, guidelines).Note• Turn on the battery switch on the PSU only after the installation of the PBX is finished and AC poweris available.• The recommended maximum capacity is 28 Ah, to maintain effective battery charge.• Make sure that the type and capacity of the 3 backup batteries are identical.• The Back-up Battery Cable should not be exposed to direct sunlight. Keep the Back-up Battery Cableand the backup batteries away from heating appliances and fire. Place the backup batteries in aventilated place.• For details about the backup batteries, refer to the manual for the batteries.Backup Power Supply DurationThe length of time that backup batteries can power the PBX varies depending on the total load figure. For howto calculate the load figure from the connected items, refer to "Load Figure Calculation".ExamplesBattery Capacity Total Load Figure Backup Power Supply Duration*128 Ah64 11 h128 5.5 h*1 The duration may vary depending on the conditions.Connecting Backup Batteries1. Turn off the battery switch on the PSU.38 Installation Manual2.2.5 Backup Battery Connection