I have a wireless alarm from response and i would like to hard wire the siren box as the sun does not catch it enough, It has a 7.5 Vdc jack socket inside that is for charging the battery up if it goes flat, can i just put 7.5v to this permently and this will keep the battery charged? Its a 6v battery aswell, or would it be better to connect the battery terminals to 6v DC?