For a 48 Volt battery pack made from 12Ah or 15Ah batteries a 48 Volt 1.6 Amp charger works very well and recharges the battery pack slowly which helps to increase its lifespan. For a faster charge, a 48 Volt 2.5 Amp or 3 Amp charger could also be used. We carry all of these chargers on our 48 Volt Chargers page.
The generally acceptable charge rate for AGM type and other sealed type batteries are between 10% and 30% of the 20 hour Ah rating. For example, if a battery is rated at 15Ah (at the 20 hour drain rate), a good slow charge rate would be 10% of that or 1.5A. However, if you are in a hurry, it is acceptable to go up to 30% of the Ah rating so in this case, as high as 4.5A. A good compromise between speed and helping keep the batteries cool and giving the battery chemistry time to mix is the middle setting (3A in this example).
The stock charger port and controller are rated for chargers up to 3 Amps so it is okay to use a 3 Amp or lower charger through the stock charger port.