To use; place the larger of the two plugs into the cigar lighter socket of your vehicle, and the other plug into your baitboat's gold charging socket.An extension cable is included with your charger to allow you to plug your charger into a 12 volt battery directly. As there is a possibility that a user may inadvertantly connect the crocodile clips incorrectly (black to + and red to -), a protective device is fitted which prevents any damage to either the boat or charging battery. The battery may be any 12volt lead acid unit with a capacity greater than 15Ah, a leisure battery is ideal. The bankside charger is designed to top up the charge on your baitboat battery during extended use, not to charge the boat from flat and because of the reverse polarity protection the charger will only charge the boat to within about 0.6volts of the charging battery. It is therefore vital that the car battery has a good state of charge. You should ensure that your cigar lighter socket is 'live', by testing the cigar lighter before using the bankside battery charger.(some cigar lighters only work with the ignition on). Some vehicles have positive earthing in which case the extension cable will need to be used directly on the battery. The length of charge required will depend on how depleted your baitboat battery is, the state of the charging battery and the temperature. You are strongly advised to use the charger in conjunction with the Baitboat battery meter as this will allow you to judge the charging situation without guess-work. It is advisable to place the boat on charge as soon as it has returned from a trip. CAUTION: The charger may become hot if used for a long period of time, this is quite normal and you should take care not to handle the unit until cool.