Initially, it had a button that is supposed to be an on-off switch but does nothing. It doesn't even work for small batteries up to 20ah. I have a better one for 12 euros. It's not worth its money at all

Fully automatic (for 12-24V), it revived a slightly discharged 60Ah battery in half an hour and then went into maintenance mode. It also revived a 45Ah battery that had been empty for a long time due to the car being idle because of license plate delivery, from 8.5 volts to full charge in 12 hours. It has 6 stages, which means it gradually charges with reduced intensity at the beginning (low power). The battery level is automatically recognized and it is commanded to charge with the appropriate power until the battery reaches a normal level, and then it is charged with higher power. This ensures maximum lifespan and protection of the battery's functional condition. Towards the end of the charging process, the microprocessor commands a low-power charging for the remaining 5% to protect the battery.

Update: 12/08/20.
When I tried to charge a friend's 7.5V battery, it didn't recognize it at all and didn't charge it. I imagine there is a limit to the amount of discharge the battery can have.

Update 2: 17/07/21.
In the case of the previous update, I managed to charge it by first starting the car with another battery and then connecting the charger to the car and leaving it for 10 minutes. I removed it and the charger immediately "saw" it and started charging it.