I have a Black and Decker 450 amp jump starter.

The car battery was dead because the lights were left on. I wanted to
use the car in the morning. I took the battery charger and put it on
the battery, the night before, intending to trickle charge it.

The next morning the car would not start and there was no juice in the
charger.

I am guessing that the jump starters are not intended to trickle
charge, although I don't see why.