I just got a istick 100w and yes I already know about ohms law and all that; however, I know not to charge the Sony vtc4's I have over 4.2 volts, but I don't have an actual charger because the istick has a micro USB charger in it. I was wondering if its safe to charge the vtc4's through the istick because I won't be able to know the exact voltage the batteries are charged and I don't want to overcharge them.