You can use one, but I doubt the breaker in it will hold up to the amount of amperage your charger is going to pull down.Is it safe to use a surge protector? Ideally i would plug both my traction pack charger, 12v charger and maybe a ventilation fan into it.
Then, all i would have to do is plug the surge protector to an outlet to charge both batteries and ventilate the trunk
I think you made a thread about this before and I suggested something like this:
I have one very similar to it and since it's made as a pretty heavy duty cord, I'd be surprised if you would cause any heat in it.