In winter, I rarely use a car, so the battery loses capacity in the cold and it is not always possible to start the engine. Decided to buy this device. I've used it several times already, both with a dead battery and with a completely discharged one. In all cases, the engine started, but only in the “Boost” mode (without it, when trying to start, the dashboard completely went out). Motor 1.6. I also tried to charge the phone with a battery discharged to 20%. After charging the phone, the JSL-12022 still showed 100% charge (although I think that it really was ~ 80% left). A good device, there is always a certainty that the engine will be able to start, but you need to get used to the features of the buttons.