Is there a way to disconnect battery w/o disabling radio?

[Stephen Bigelow]

> I remember seeing a product in a BMW catalog that plugs into the cig
> lighter and allows one to disconnect battery w/o having to re-code the
> radio.  Has anyone seen/used this product and will it work on the newer
> Audi's?  Thanx.

It's a battery pack (AA's, maybe), supplying enough juice to keep the memory
alive, but not enough to shock anyone, or start the car.