Never leave your automobile battery in a discharged state

When a automobile battery has been fully charged it can quite happily be stored away for 2-3 months. However when it is flat, storing it for this period would almost certainly damage it beyond repair.

The reason behind this is a chemical process called sulphation. When a automobile battery is charged this chemical process cannot take place. However, when the battery's voltage falls below 12.4V this process begins. The process causes sulphur crystals to form on the lead plates inside the battery, which in turn increases the battery's electrical resistance. The longer this process is allowed to continue the worse the effect. Eventually the battery will become so electrically resistant, that you will be unable to charge the battery, let alone draw power from it.

If this process is caught early you may be able to salvage the automobile battery using a battery charger with a pulse charge function. This will partially break down the sulphur crystals but the battery will never reach its full capacity again.

Remember that if your automobile battery fails due to sulphation it will not be covered under warranty. This kind of failure is classed as damage caused by the user through neglect.

So take care of your automobile battery, and it will take care of you.