on 09/05/2017, Brian Gaff supposed :
The lighter is not going to sink the sort of current you need to charge it
really, and yes you could current limit this by a simple circuit (Look in
many of them old Bibani Books!)

It may not charge at full speed, but charge it would.

I'm sure little modules exist for this nowadays.

No need, the resistance of the wiring and the small voltage difference
between vehicle battery and car battery will provide an effective limit
to the charge current.

I would no want a battery on charge in the passenger compartment.