The voltage rating of a car adapter is the maximum amount of voltage that the adapter can provide. If you connect a device that requires more voltage than the adapter can provide, the adapter will not be able to power the device and the device may be damaged.
The amperage rating of a car adapter is the maximum amount of current that the adapter can provide. If you connect a device that requires more current than the adapter can provide, the adapter will not be able to power the device and the device may be damaged.
In this case, the 4.5v 2000ma car adapter cannot provide the 5v required by the device. Therefore, the adapter will not be able to power the device and the device may be damaged.
If you need a car adapter to power a device that requires 5v, you should use a 5v 2000ma car adapter.
