Our DC9091 / DW9091 battery replaces DeWalt OEM battery part numbers: DC9091, DW9091, DW9094, DE9038, DE9091, DE9092, DE9094, DE9502.
Capacity: 1500mAh / 21.6Wh
Color: Black / Yellow
Warranty: 1 year
Compatible models:DeWalt Cordless Drills and Drivers:
Is a DW0991 Battery compatible with a DC9091 Battery .
The DW9091 is the same battery as DC9091.
I am not sure if you misspelled the model # in your question or specifically were asking about "DW0991"; I don't believe DeWalt has ever produced DW0991 battery.
Can I use the DEWALT DW9107 7.2V-14.4V Battery charger on a DC9091 14.4V battery.
Yes, you can. The DW9107 is compatible with 14.4V batteries. Please note that some DeWalt DW9107 chargers were on a recall at one point. Make sure you use a properly functioning one.