Vehicle alternators are a very basic battery charger, they can recharge you vehicle battery if it is not deeply discharged. If your battery is deeply discharged it is highly recommended to recharge on an automatic or “smart” charger. These chargers have multiple stages of charging and some offer different modes depending on the type of battery you are charging. Wet, Calcium, AGM and Gel batteries all like different voltages check with the battery supplier for more info on suggested charge voltages.
Before charging check the electrolyte levels and top up with distilled water if necessary. Connect the charger leads to the battery terminals red positive lead to the positive terminal and the black negative lead to the negative terminal, make sure they are on the correct terminals it is possible for the charger to reverse charge the battery if hooked up incorrectly. Only turn on the charger once it is connected to the battery. Never touch the charger leads when the charger is on and turn the charger OFF before disconnecting the leads.
Batteries should be monitored whilst on charge, if the battery is faulty there is a good chance the charger will not switch off and the battery will overheat and be overcharged. If the battery has a faulty cell the charger will continue to charge the battery until a predetermined voltage in the charger is reached. If the battery has a faulty cell the charger cannot reach this voltage and will continue to charge until it is manually switched off. You must be very careful when handling the battery in this state as a large amount hydrogen gas would be around the battery and any spark can set off an explosion.