Those Watson changers are cheap, and have the convenience of being compact and with inexpensive adapters from B&H, but on my last trip out of the US, I regretted relying on one for my AW1 (+D5100 which I did not use much), as it quickly died, and cost me a new extra Nikon charger for the AW1. I eventually got a warranty replacement after my return to the US, but the Watson has only two terminals, so it is a simple charger with just voltage cutoff, and no connection to whatever smart circuitry may exist in the battery for distributing charge between the cells and measuring battery state. It might have just been a coincidence, but one of my EN-EL15 broke (one of the cells went bad) shortly after I did a single test charge with the Watson (I normally use the original Nikon charger); that battery was only about a year old. So the Watson is now retired to only be a backup charger for emergencies (the adapters are convenient in that respect).