I purchased the VTOMAN V2500 Jump Starter for emergency use during winter in Ottawa. The unit was fully charged according to the indicator lights before use.
Unfortunately, at around -2°C, it was unable to start my car. The car has a standard 12V battery and is well within the advertised limits (gas engine). I followed the instructions exactly, ensured proper cable connection, and even tried multiple attempts, but the jump starter did not have enough power to crank the engine.
Given that cold weather performance is critical for a product like this—especially in Canada—this was very disappointing. A jump starter advertised for large engines should reasonably handle mild sub-zero temperatures, and -2°C is not extreme winter weather.
The unit may work in warmer conditions, but based on my experience, I cannot rely on it when it's actually needed most. I would not recommend this product for anyone who lives in a cold climate.