Well after some go around with Whistler on their new 445 battery operated radar detector. Here's information they do not provide in their owner's manual.
"If the 445 batteries are dead, they cannot be charge in the radar unit. They must be charged on a home charger unit.
This is what the original instructions say with the unit.
Unit requires 3 AA rechargeable batteries (included).
Unit must plug into a live lighter socket to
fully charge the batteries overnight before first
use! Remove the battery compartment cover
by sliding the cover to the edge of the unit
and lift up. Insert batteries and reinstall battery
Ni-MH rechargeable batteries should be used
and are included with the unit.
Note: DO NOT mix battery types as this can
damage the batteries.
Important: Use only NiMH batteries. Ni-Cd
batteries should not be used.
Caution: Only use rechargeable batteries.
Charging non-rechargeable batteries can
damage the unit or possibly cause the batteries
to explode. See battery charging section
(page 6) to charge batteries with the power
No where does it say must be charged in a home charger when batteries are dead!