Garmin nuvi 255 w is less than 2yrs old and will not turn on.either when pluged in to lighter or not.

Hi, plug the unit into the cigarette lighter. Then with the key in the ignition, please place it in either on or accessory mode. Next please do a reset to the unit. The reset can be done by doing the following:
Press the Reset button on the Bottom of the GPS. If the reset button is not present press on hold the power button to the left for 10 seconds.
**Note**-This reset will only reset power to the unit.

Now try to power on the unit. If the unit still doesn't power on, it may need a complete charge.
To charge the unit, please start by plugging in the USB cable to the computer tower. Then plug the mini USB cable end to the right side of the N?vi. Next reset the unit (as done above). After which let the unit charge from the computer for about over night (7-8 hours) this will fully charge the unit. After the charge you should be able to unplug the unit from the cable then power on.

If it does not come up, you have a defective battery...