In order to properly test autonomy of the very small and low power IBBS battery you must be sure to remove the feed from pin 6.
If you don't, the screens will recieve "feed through" power from the main ship battery.
Many people wire pins 1 & 6 in parallel. This essentially puts both batteries in parallel and you will never fully see or test autonomy of the IBBS without disconnecting pin 6 or depleting the main ship battery.
I have little faith in the small cells within the IBBS, but do like the circuitry within the unit. My plan is to keep the IBBS but export the battery leads out of the box to a remotely located, equally sized fire alarm battery.
I know of another RV who has done this and no smoke was produced!