When I got the alarm system service required on the T5 - it turned out to be the siren...but when I pulled the siren (thank you Howard for the directions), the board was fried...not chemically, from a leaking battery, but it looked like it had really overheated. New siren, all was well...just be careful drilling out the rivets - easy to get them hot, then they melt the plastic and spin...
But I agree - the battery should be replaceable.
2016 Tundra Crewmax 4WD 1794
2005 MB S600 (90K, Michelin AS3, M1 0W40)
2002 V70-XC (218K, AltiMax RT43, Castrol Edge 0W40)
2002 V70-T5 (189K, IPD bars, Bilsteins, Contis, Mobil 1 0W30)
1932 Packard Sedan (straight 8, dual sidemounts, original paint and interior, Shell Rotella 15W40)