In combination with the uninterruptible KNX power supply, the lead gel battery serves for the buffering of the system voltage. Max. two lead gel batteries can be connected in parallel to the power supply. In that case two equal lead gel batteries must be used. For the connection of a single battery the 4-wire cable set must be used, for the connection of two batteries the 4-wire cable set must be used for the first one, the second one must be connected with the 2-wire cable set. The durability of lead gel batteries is up to 5 years.