Streamlight stinger charging oddity

Hello everyone. I acquired one of these lights but no charger. I've been removing the battery and charging it with my hobby charger. My question was charging it in the light and wondering if there's any electronic trickery built in. The voltage will quickly spike to over 5v yet it's a 3x sub-c pack and when there's no charging current it drops to 0 volts. Out of the light it charges like I expect a 3s NICD battery to. Any idea what is going on. It's a polystinger led btw

Thanks fivemega. That's what I figured. Having a proper charger isn't a big deal. Unfortunately I can't seem to find a charger for it that isn't priced almost as much as a new light with charger. Not without big shipping charges to Canada anyway. It's easy enough to remove battery and charge with my hobby charger and magnets. I'm really liking the super flat discharge of the NICD battery. May build a new battery with 3x 5000mah elites. No need as this gives all the runtime I need but will be fun. For an led this thing throws an incredible beam