The camera does remain on and records in normal mode.
First, ensure that there is a secure connection in the cigarette lighter socket.
If so, it could be that the voltage in your vehicle's onboard electrical system is momentarily dropping below 10V — possibly due to the operation of a "smart" alternator, a start-stop system, specifics of a hybrid system if applicable, or similar factors.
The UPS is smart/adjustable and it is configured with preset voltage thresholds for switching modes as follows:
When the primary input voltage (from the vehicle) drops below 10V, the UPS immediately disconnects the primary power source and switches to the backup source (River3).
Conversely, when the primary input voltage rises above 11V, the UPS reverts to using the primary source.
You need to lower the 10V threshold for the primary input voltage.
This can be done by adjusting the potentiometer labeled "UVP"—specifically, by turning the adjustment screw clockwise by 2 to 3 full turns.
Test the vehicle/camera; if the issue persists, continue turning the screw until the problem is resolved.
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For additional information on configuring the UPS, please refer to the post at the following link.
(In this example, we needed to increase both the primary input threshold and the recovery input threshold, precisely measuring voltages—the recovery input threshold shall always be higher.)
@IgorTa
Farther evaluating the UPS for your setup, I think you actually can use this UPS, but you will need to fine tune it for your desired UPS cutoff/switching and recovery voltages.
The UPS ships from the factory with preset settings: it switches to the backup power source when the voltage drops to 10V, and reverts to the main power source at 11V.
These voltages correspond to 2.0V at the UVP pin and 2.2V at the Vstart pin (based on 1:5 ratio), which can be adjusted to the required range via corresponding potentiometers.
See attached image for product description.
Operating...