There are two versions of the cordless Stanley FATMAX 18V tools – the original and the V20 range.

The V20 range is clearly marked with V20 on the batteries, chargers and tools. The batteries are not interchangeable.
The original series take the N496096 2.0 Ah (previously FMC687L-XE) and N552567 4.0 Ah (previously FMC688L-XE) batteries. The charger is 90611165-02 (previously FMC692L-XE) – The adaptor SFMCB100-XE will convert the 2.0Ah V20 batteries to allow them to fit the original series tools.
The V20 range take the SFMCB202-XE 2.0Ah and the SFMCB204-XE 4.0Ah batteries. The V20 charger is the SFMCB14-XE.