Ditto here. I wrongly didn't think it was an automotive charger that was being discussed because it was not stated as such up front. Shame on me. Car/ trucks/boats are lead-acid batteries. I had thought of a small electronics charger.
To the OP:
If you didn't observe polarity, causing a short w/ arcs and sparks and your battery isn't charging, then it sounds like you may have damaged the charger.
Generally speaking in a car or truck, the positive terminal is marked with a plus, negative minus...Battery charger cables are generally red for positive and black for negative.