I think he's just worried about leaving the charger plug'd in the whole time. I believe this is the same as leaving your house' heating on (lower setting due to freezing concern) while on vacation or the other appliances for that matter. Fridge's compressor will run when it needs to and stop when it's cold enough. Reversed for your furnace. Same logic w/ the trickle charger. Except maybe for the hydrogen that's released as one charges a battery? Don't they suggest that there's some level of ventilation while this is done? I'm sure it's a very tiny percentage and is more for the legality of putting a warning to protect the manufacturer—lawyers. I agree w/ F87 but I don't have a surge protector on mine.
