My electric bike is my primary mode of transportation so I need to be able to ride it under all conditions and at night that means I need light, lots of light. It seems silly to me to have a separate battery to power the lights when I have this nice big battery for the motor and it would be one more thing to remember to charge. The hiccup comes from the fact that the bike battery is at 48V (with a soon to come upgrade to 80V) so a switching power supply is needed.