i have a device that runs on 10.5v DC at 1.2 amp...
can i put a wire connecting to the car battery to the device to power it up??

will it blow???

 

Most devices have an over/under current tolerance built right in, but usually that variance is only a couple of volts either way... If your charging system is good, and puts out the 13.8-14v it should, then you may want to buy a universal adapter with a step-down transformer, that'll give you 10.5 or 11 volts...