Battery wire is healthy. I have an IMAX B6AC charger. How do I know if there is a dead cell in the battery?
Battery does not looks damaged or swollen. That is good.
Due to the blow there may be some unsoldered wire inside. Don't try to check it by pulling the wires, you might short them.
Get a multimeter or a lipo-battery checker like this one
and mensure your cells independently using the Balance lead of yout battery. Your Balance lead has 4 wires, try measuring the end wires with the multimeter first. It should give you some voltage. Otherwise, one of the cells is dead and it's interrupted by the current.
If this is the case, measure each pair of wires, as follows:
1 y 2, 2 y 3, 3 y 4
Each pair corresponds to a cell, if one or more of them does not give voltage, is that they are dead. or in the best case, some cable has been desoldered.
Once you have identified the dead or defective cells, it is at your own risk to open the package and carefully check the connections. I recommend that if you have no experience with electronics, you seek professional help. If something goes wrong, things can get very ugly.
Lipo batteries are something to be respected.
try at least to identify which cells are in trouble and come back here to preceed.