SkipD - that's what I have, the breaker that I'm taking the N1 and N2 off of will be powered by the generator after I manually disconnect utility power, so I guess the question still remains - can I take the T1 off of one side of the same breaker to run the battery charger? Since this is a manual, interlocked disconnect system N1 and N2 are only being used so the test mode will function (Generac says you have to have N1 and N2 connected to be able to use test mode).
The bottom line is this. If that breaker will have power on it whether in utility or gen and the breaker is listed for two wires under one terminal. Then yes you can. It will tell you on the side of the breaker. Most will allow 2 copper conductors but only 1 alum.