According to an article about batteries posted on the environmental website Green Trust, a rating of 12 to 20 amps is preferable for charging deep-cycle batteries like car batteries. In addition, Green Trust recommends charging depleted batteries as soon as possible to avoid long-term damage.
Chargers Offer Options
Though Green Trust recommends using 12 to 20 amps to charge car batteries, battery chargers typically offer rates that range from two to 30 amps. Larger amperage charges a battery more quickly, according to the British battery website Mr. Power UK, and amperage requirements may vary, depending on the charger's delivery method.
Though chargers vary considerably in their available amperage and charging methods, a charging rate of 12 to 20 amps is preferable for long battery life.