What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Standby Battery Master Switch purpose

mfleming

Well Known Member
Patron
This has me a little confused.

Here is a snippet of my avionics wiring drawing showing the TCW IBBS backup battery.

What does the Switch labeled "Stby Bat Master" on pin 1 do?

The power comes in through a 5A breaker on pin 5, so opening the switch doesn't seem to kill the juice going into the battery. The juice leaving the battery is hot all the time (it seems).

Is there internal circuits to control the power input by opening or closing the switch??
 

Attachments

  • battery.jpg
    battery.jpg
    76.3 KB · Views: 116
Controls internal circuitry that disconnects the TCW backup battery outputs from the connected equipment. Enable the BU battery before you start the engine. Disable before you walk away from the aircraft after a flight.

Here is the description in the TCW manual for the switch.

5. The Back-up Power Master switch must be utilized to turn the back-up battery system off when not in use, except for installations where the off state current requirement is less than 50 micro-amps, such as with the AFS EFIS systems. Follow the specific wiring diagram for this application. This back-up power master switch gives the pilot the ability to turn the back- up battery system off. In some installations this may be the only means to shut down the connected equipment.
 
So it does not look like the "back-up power master switch" kills the incoming power to the back up battery.

I was going to put this unit on a fuse but now I'm thinking a pullable breaker. If for some reason the IBBS started acting up, one would want a positive way to kill the power to it I would think.
 
Battery

I can tell you that if I shut the master off with that switch on, the backup battery powers the attached equipment. In my aircraft, that switch must be turned off prior to turning off the battery master.
 
So it does not look like the "back-up power master switch" kills the incoming power to the back up battery.

I was going to put this unit on a fuse but now I'm thinking a pullable breaker. If for some reason the IBBS started acting up, one would want a positive way to kill the power to it I would think.

From your wiring diagram, pin 5 is only being used to provide charging current for the TCW internal batteries. Having a pull able circuit breaker would be a good idea, that way you could positively disconnect the TCW backup battery from main ships power in case of an internal failure.
 
Could you share the full interconnect diagram?

This has me a little confused.

Here is a snippet of my avionics wiring drawing showing the TCW IBBS backup battery.

What does the Switch labeled "Stby Bat Master" on pin 1 do?

The power comes in through a 5A breaker on pin 5, so opening the switch doesn't seem to kill the juice going into the battery. The juice leaving the battery is hot all the time (it seems).

Is there internal circuits to control the power input by opening or closing the switch??
 
So it does not look like the "back-up power master switch" kills the incoming power to the back up battery.

I was going to put this unit on a fuse but now I'm thinking a pullable breaker. If for some reason the IBBS started acting up, one would want a positive way to kill the power to it I would think.

I just installed the 3ah version...this is probably a good idea. Thanks!
 
Back
Top