I am installing the TCW back-up battery for my 5400s (upgrades to my 4500s that included internal back- up batteries). The wiring diagram and instructions show the use of pass-thru power (pins 6,7,8 on the TCW) with a 10amp circuit breaker...is this necessary (in the footnotes it indicates it is optional)?

The existing 4500s are powered off the master bus. So, I thought I could just run power into the TCW on pin 5 off the master bus with a 5amp circuit breaker (for charging the TCW) and take an output from the TCW to pin 6 on the expansion connector of the 5400. Do I need the additional wiring and circuit breaker for the pass-thru?