Hello group. I need some info. I know nothing about ebikes. I bought this a2b hybrid and it has extra ultramotor battery. I see no where for a key. It didn't come with a charger. Do I need a battery charger for the battery in the bike? If so,where do you plug in charger? If I buy a 3 prong charger does it go into the back battery? Where I unplug the back battery is a 5 or 6 prong. Do I unplug that to charge stock battery? Hope I'm making sence. Will I need 2 chargers?