I will admit that i purchased an inexpensive trickle charger years ago, but the few times i have used it i removed the battery from the Buick and charged it away from my garage using a lamp timer ( set for 8 hours) plugged into a surge protected power strip that's plugged into a properly grounded extension cord. I also disconnect the battery cables when the Buick is not in use. I do a battery load test every year, if the battery is weak i simply get a new one. I get 5 to 6 years out of a Delco battery. And i trade in the old batteries. I don't like keeping old batteries around my garage, that's just another disaster waiting to happen.
The only problem with a battery accessory I've had was with one of those battery disconnect switches, My wife (then Pregnant) & I were on the NYS Thruway heading to the BCA National meet in Buffalo NY in 2001. And i thought i smelled something electrical burning so i stopped at the next rest area, opened the hood of the White GS looked around everything looked OK. When i got back in the GS it would not start, totally dead ! I looked under the hood again and checked the battery terminals and the disconnect switch , everything was tight. I loosened the disconnect switch looked at it and saw that it had burn marks from arcing. I removed it threw it in the garbage and never had a problem since then. I'm glad that i caught it in time before it damaged my GS and ruined my vacation.
Tony