Garmin 78 off Battery tender cable??

[gumbellion]

Is it possible to run my garmin 78 off of the cable that I already have running on my bike from the battery that is used for the battery tender?
I figure it would be pretty nice if there is a way I can do this without wrecking the unit.
My idea was to get the "ciggarette lighter" power plug and cut that end off, then add on a connector the same as the battery tender end.

Any suggestions or ideas are welcome. I already have a BMW plug that I would like to keep for my heated gear or anything else I have, while also running the GPS. I also have a tender on my snowmobile so i would be able to move the unit from my bike to sled with the seasons without doing anything