Being an electrician since 1976 I will attempt to resolve this matter (I think)
without putting an amp meter on the incoming charging wire it is very hard to determine the current draw.
I do know that the maximun current of most usb devices is 500 milliamps or 1/2 amp. Wattage equals volts times amps or the usb is regulated to 5 volts times 1/2 amp for a 2.5 watt draw.
This still will not answer what is the draw of the tomtom
I then worked this backwards on the 920 which has a 1320 milliamp battery.
If we take 5 volts times the 1320 milliamp battery we get a total battery reserve of 1.32 amps times 5 volts or 6.51 watts for the battery from complete full to absolutely empty which would make the battery dead.
If we now say the battery will last between 3-5 hours and use 3 hours to be on the safe side we can calculate the average draw on the battery to be 6.51watts divided by 3 hours or 2.16 watts per hour
We now take this 2.16 watts and divide by the 5 volts which is the constant and we now get the average milliamp draw which would be 431 milliamps or about 82% of a 500 milliamp draw.
Thus a 500 milliamp power supply such as the motorola would give 82% to power the unit and the remainder of power would go to charge or maintain the internal battery.
As for the question of the 2 amp fuse this is only an inline safety device to prevent fire etc. This is simular to your home service that is protected by 15 amp circuit breakers as the standard fuse protection even though you may only have a 60 watt bulb plugged into it.
hope this helps out a bit.
without putting an amp meter on the incoming charging wire it is very hard to determine the current draw.
I do know that the maximun current of most usb devices is 500 milliamps or 1/2 amp. Wattage equals volts times amps or the usb is regulated to 5 volts times 1/2 amp for a 2.5 watt draw.
This still will not answer what is the draw of the tomtom
I then worked this backwards on the 920 which has a 1320 milliamp battery.
If we take 5 volts times the 1320 milliamp battery we get a total battery reserve of 1.32 amps times 5 volts or 6.51 watts for the battery from complete full to absolutely empty which would make the battery dead.
If we now say the battery will last between 3-5 hours and use 3 hours to be on the safe side we can calculate the average draw on the battery to be 6.51watts divided by 3 hours or 2.16 watts per hour
We now take this 2.16 watts and divide by the 5 volts which is the constant and we now get the average milliamp draw which would be 431 milliamps or about 82% of a 500 milliamp draw.
Thus a 500 milliamp power supply such as the motorola would give 82% to power the unit and the remainder of power would go to charge or maintain the internal battery.
As for the question of the 2 amp fuse this is only an inline safety device to prevent fire etc. This is simular to your home service that is protected by 15 amp circuit breakers as the standard fuse protection even though you may only have a 60 watt bulb plugged into it.
hope this helps out a bit.
