When I repaired the Becker 1432 on my 400E by myself, a stuck relay in the radio drained about 0.4 amps current, my battery ran out when I left the car in the garage over the weekend.
10 Amps is not a small current, 120 Watt in power, something may be fried by this, if the thing can constantly stand for such high power, it must be quite big in size so it can sink the heat. It's not likely that small alarm unit can stand for 120 Watt power, sounds like they screwed up your car when installing the alarm system, probably there is a short in the alternator.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.