(1)Remaining power of your battery is no less than 60% before attaching it
(2)This item is just battery maintainer, keep a battery topped off
(3)Make sure a “live” lighter socket: the socket gets power at all times from the battery, you can test this by plugging in a phone charger or other accessory with the ignition off--if the accessory turns on, that means the socket is "on" at all times.
(4)For modern vehicles, there are body control modules (computers), alarm systems, immobilizers and lock monitoring. All of these units will rob electricity from the battery when it is not in use. Also, cars batteries naturally discharge itself when not in use. For such cases, it is suggested to leave the battery charger connected with batteries for the whole off-season to offset the nature loss, but for vehicles outside the garage, an off-gird solar battery maintainer may be the best choice.