Yeah that's also the thing i like about the heating pad - it's really hard to overdo it, even if it takes a while for the heat to penetrate down to the glue. I experienced thermal runaway in a damaged LiIon battery once on my old phone (thought i could use leverage to remove the battery, but it shorted internally) - i was just fast enough to throw it in a bucket and place it on our tiled terrace and watched the fireworks.