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DNK76, yes, ISTA documentation suggests using 14,8V BUT on CHARGE mode. Charge mode monitors current, and when current drops below specific limit, it drops voltage automatically. Like in attached picture. If you put 14,8V without charge-current limiting and supervision, you ARE potentially KILLING the battery. Safe long term voltage as shown in the picture is 2,3V per cell so about 13,8V. I would never supply more than that in supply (not charger) mode.

Car itself (when talking about cars with S1CC and S1CD) also monitors current going into battery and will NOT increase voltage to 14,8V when battery is sufficiently charged. Cars without those options will not increase voltage above 14,0V.

P.S. These voltages are for 25°C. When battery is colder (and IBS also monitors that) the voltages are higher. Like 15,3V charge/14,4V float at 0°C. At 40°C - 14,3V/13,4V.

P.P.S. These numbers are for compatible AGM batteries. Flooded batteries and cheap AGMs (hence the question in ISTA when you are registering battery change: are you installing BMW or generic battery) are more sensitive. Hence ISTA documentation tells you to use lower voltage for E series, because they rarely have quality AGMs installed.

P.P.P.S. Regarding "100A is generally about 13V on the termnal in the car": quality automotive chargers (so all those listed in ISTA documentation) increase the voltage when current increases to have the specified voltage on the clamps. They either have cable calibration mode when you short circuit positive and negative clamps so they can measure cable resistance or that is hard programmed into them.