I want to buy a battery for my D500 and I’m not sure which one to get. I see on Amazon an en-el15, an en-el15a, and an en-el15b. They all say they will work but I’ve heard conflicting reports. It looks to me like the b came out for the Z6 and Z7. If all work, is there one that lasts longer or has any other advantage? Thanks in advance.