How many kWh to fully charge a battery?
Start by computing just the energy that will be stored in the battery.  (11.6 Ah)(48 V) = 557 Wh = 0.557 kWh.

However, there are various losses along the way that are hard to quantify.

The Ah rating of the battery is what it can supposedly deliver.  It's what comes out, not what you have to put in to get that out.  No battery is 100% efficient, so you have to put more in than what you eventually get out.  The efficiency is hard to know, and is usually not specified well or at all by the manufacturer.  The charging sequence also makes a significant difference.  For example, if it ends with a "top off" slow charge, most of that energy won't be stored by the battery.

Then there is the efficiency of the power supply that generates the required voltage and current to charge the battery.

Overall, I would not expect more than half the energy into the charger to eventually come back out of the battery.  Therefore, I'd consider around 1 kWh the minimum required energy, but somewhat more is also quite possible.