UltraGauge Battery Drain
UltraGuage draws power from the OBDII connector, which in turn is drawn directly from the battery. The power at the OBDII connector is always hot and the position of the ignition switch is not a factor. When active, UltraGauge draws much less power than a GPS or a charging smart phone.
UltraGauge gathers all its information by communicating with the vehicle's computer. When the ignition is switched from RUN to OFF, the vehicle's computer is powered off. When the computer loses power, UtraGauge detects this and enters a low power mode where the backlighting and LCD are turned off.
This RUN to OFF auto-detection is disabled while in the Menu system and when UltraGauge is first attached and is scanning to find the computer and its protocol. As a result UltraGauge should not be left in the MENU system or scanning while you are away from the vehicle.
Even in low power mode, UltraGauge does draw a little power, about equivalent to that of 1/250th of a 60watt light bulb. It is much less than a glove box or vanity light. The average low budget car battery has about 50A hours of energy. In low power mode, it would take UltraGauge roughly 2500 hours or 104 days to completely drain such a battery.