Before you buy this thing, do yourself a favor and look around to see if you can find a newer charger. Unless you can find someone who can scan or copy the manual for you, you won't get instructions. Repairs will probably be impossible for you to do (someone will have the email for the guy who used to do Tekin repairs). Upgrades will also likely be impossible. You can power the BC112A off the C, and possibly other chargers as well, but it has a 24v power supply, not 12v.
I would highly suggest you find something else that is newer. Tekin has been defunct for years now, and unless you are getting a GREAT deal (like, less than $30) for the 112C I would get a different peak charger. Just make sure it can handle Ni-MH batteries.