The PBSA 12 B1 comes with a DCBK-70-12 (1,5 Ah) battery by default. Mine died over the years (since 2017 when I've bought it). I bought a new B3 12V 4 Ah battery from the same brand, but they've made some slight modifications (alignment rails in a different position) so it does not fit by default.
I've made this small enclosure design that makes it compatible with my old PBSA 12 B1.
On the prototype print I've forgot to mark the “+” and “-” so I used a label to not mess up when I install it into the charger as I haven't created any alignment pin/rail for the enclosure. In the model I've added the marking, however as the prototype works fine I haven't tried to reprint it just for this.
For me it fits well inside the screwdriver, while for the charger it is a bit tighter fit. It is just fine so be aware of that. Tolerances may be different for yours.
The author marked this model as their own original creation.