Unfortunately, I think it is fried. Most of those CDI units really meant that 6.0v is the max that can be applied to them. Any higher voltage and they die, usually quietly sometimes with lots of smoke.  You have to ensure that the peak charged voltage of a battery pack does not exceed 6.0v too. Some CDi's are sensitive to the high voltage spike that could come out of a voltage regulator when power is turned on too. So one needs to be careful using the regulators to lower the voltage to 5v.  A 4.8v battery pack is more than enough to operate these CDi's. higher voltages merely increase the current draw but do pretty much nothing to improve performance.