I have an inexpensive RC Monster truck. The battery is a sealed lead acid 12V 2100 mAh/ 5hr. The charger is just an AC/DC adapter with a connector that matches the battery with output of 12V 25o mA. Will it hurt to leave the charger plugged in overnight? Also does anyone know where I can get a similar battery, or is there a better battery I can use? Thanks, Gary