A 9V charger cannot charge a 12V lithium battery.
If you use a 9V charger to charge a 12V lithium battery, not only can you not charge the lithium battery, but the 12V lithium battery will slowly discharge through the output end of the 9V charger until the voltage is discharged to 9V. When the voltage of a single lithium battery is reduced to 3v, there is damage to the battery, which is prone to the problem of unrecoverable capacity, and the battery capacity becomes smaller when recharging.
Therefore, it is best to use a special charger for lithium batteries to charge lithium batteries. When charging, you also need to pay attention to safety to avoid dangerous situations such as overcharging and overheating.
No, the 9V charger can only charge the 9V battery, not the 12V lithium battery. Charging with a mismatched voltage can cause damage to the battery and can lead to safety issues. The correct approach is to charge a 12V lithium battery with an adapted 12V charger to ensure that the battery can be charged safely and efficiently. Therefore, in order to protect the safety of the battery and charging device, you should always use a charger that matches the specifications of the battery.