6/12V 4A Auto battery charger/maintainer - This vehicle charger automatically performs the charging function in 9 stages. The first 5 stages perform diagnostics and recovery depending on the condition of the battery. After recovery, a bulk charge brings the battery up to approximately 80% of capacity. This stage is followed by a low current charge up to almost 100% capacity. The final maintenance or conditioning stage will pulse low charging current, cycling between trickle and maintenance modes to keep the battery in top condition over a long period, The charger can be left connected to the battery in order to perform this maintenance function.