Charge them at the track. Never do so the day before. You get better punch as well if you charge just before your run. Time it right and you'll get a small advantage. Plus why would you charge 'a bunch of lipos'. You only really need 2 on the bench. One in the car ready to go and the 2nd hooked up (and in the lipo pouch!) ready to charge at the right time for the next run.

While we are at it. Never charge a lipo inside the house and never charge one that is not in a lipo sack!!