The unit of battery capacity is mAh (milliamp-hour), and the unit of current is A (ampere) or mA (milliampere). The two are not the same physical quantity, and the battery capacity is not necessarily related to the charging current.
The current value of the mobile phone charger of many power adapter types such as vehicle power adapters (in fact, it is more appropriate to call the power adapter) is the maximum output current, not the charging current, and it should not be confused. The charging current of the battery is controlled by the charging circuit inside the mobile phone and is not determined by the adapter.
Therefore, the higher rated maximum current, the higher the output current, the higher the power of this adapter, and there is no problem to replace it with other low-power adapters with the same voltage, and there is no saying that "high-current adapters shorten the service life of battery". In addition, there are regulations in electricity that the high current can replace the low current power supply with the same voltage, but the reverse is not possible, because if you use a particularly small power adapter to charge, the adapter may be in an overload state, which will burn the adapter.
The output voltage of the power adapter, say 9v 1.5a power adapter, needs to be equal to the input voltage of the electrical equipment (or the electrical equipment clearly indicates that the input voltage is within a range and the output voltage of the adapter is within the range).
The output current of the power adapter is the maximum current that the adapter can output, and the actual output current is determined by the electrical equipment. (Simply speaking, it depends on the impedance (external resistance) of the electrical equipment and the internal impedance (internal resistance) of the power adapter I=U/(R in+R out)).
The (maximum) output current of the power adapter actually characterizes its internal resistance (the larger the output current, the smaller the internal resistance, that is, the adapter itself consumes less power and more power can be reserved for external use).
Therefore, whether it can be used interchangeably depends on the nominal input current of the electrical equipment. If the nominal input current of the electrical equipment is less than the output current of the power adapter, it can be used. Otherwise, it cannot be used, but the equipment will not be damaged if it is used.