The light on the INTELLIBOOST cables will not turn green if you connect it to a fully charged battery. This is for safety reasons, because if the voltage on the battery that you are connecting it to is higher than the voltage of the jump starter, then power would flow back into the unit. If you want to test your jump starter but don't have access to a vehicle with a dead or low battery, the best option is to disconnect the red "+" positive terminal from the battery and connect the jump starter cables directly to the battery wire, bypassing the vehicle battery completely and allowing you to start it right up.
