Then just charge it to 4.05V and accept the battery will never be fully charged, and compromise on life slightly. If charging on USB that would be the likely case, as it will take 4 days to fully charge the 5AH cell from a standard high power USB current of 500mA. It would probably be good to have an external 12-19V input to a separate charger chip, which will enable it to be charged from a laptop PSU easily, and will satisfy most users. Charge time on that would be under 2 hours, and it would be usable while charging ( though at the expense of higher output noise though) without killing USB power delivery, allowing use on a unpowered hub ( common laptop limited ports).