If it’s a new lead-acid battery, check the fluid level in EACH cell. The dealer may have missed filling one or didn’t fill it completely. If it’s a maintenance free battery, I would put it on a charger for a few hours to see if it will charge up and then test it again after a day (not connected) to be sure it’s holding the charge. If the voltage drops below 12 volts, I would return it to the dealer for a replacement.
IMHO, you don’t have to disconnect the battery between trips unless you have a habit of leaving the lights on, or the refrigerator on, or some other device like a charger for cell phone/computer battery. If you have enough of those devices turned on, they will discharge your battery. In that case – disconnect it.