so 2Ah really means “2 amp-hour”. it measures how much of a charge it has- basically, you can draw 2 amps for one hour from the battery during ideal conditions (IE, it’s not an old battery, and everything about it is perfect- perfect temp, perfectly isolated from vibrations. all sorts o things. We never see that in the real world, however.)

alternatively, you could draw 1 amp for 2 hours, or 4 amps for half an hour.

1.5 amps is the amount of charge it’s providing to the battery, again, under ideal conditions (like temperature, etc.) a 1 amp charger would charge slower where a 2 amp charger would charge faster.

The important thing is that the voltages match- 12v or 18v tend to be the most common. if the charger has too much amperage, it’s fine- the battery will only draw what it can use; too little and it’ll just take forever to charge.