Energizer - Recharge Universal Compact Battery Charger - Black

This is the way that the charger indicates a non-permitted circumstance, such as one cell being shorted, a mismatch of cell types, or the like. They don't say just how they implement this, but the charger charges cells in pairs, not singly. To make it work for three cells, I had to make a dummy ballast to add to the compartment where I have only one cell, and I still don't know if the charge current is right, but the error indication does not happen, so I hope that all is well.

yes

Yes it charges 9V, there is a battery peel indicator.

Yes, you can charge 4 D cell batteries at the same time.

Yes, i bought mine in best buy SC. You can also buy online.