Nikon did some kind of change between the EN EL 15 on the the D800, and the one on the D500.  The older batteries do not work on the newer cameras. However, Nikon will exchange the older EN EL 15 'Li-ion01' for the new 'Li-ion20' ones free of charge. I had two of the older ones, on their last legs, and now have two brand-new extra bats.

A free fresh exchanged  battery is great if you can take advantage of the opportunity.

-------------------------------------------------------------------------------------------------------------
Nikon probably added or changed a product ID chip,   That technology is widely used with toner and ink cartridges to force the user into future OEM sales.  Those can be more lucrative than the original product sale.


Some of the aftermarket batteries already say D500 compatible -- others definitely say they are not,  so it is already a solved problem..  Trouble is, they can make changes with every new camera model introduction.

yes
http://www.ebay.com/itm/1400mAh-Battery … 2352690257
http://www.ebay.com/itm/Power2000-EN-EL … 1660010535

no
http://www.ebay.com/itm/Battery-for-Nik … 1012451132
http://www.ebay.com/itm/Battery-Charger … 0972256690

They possibly had problems with the old ones, which had to be changed due to new regulations. I had two that aged to "1"  only after a few uses, then caused the power board on my D800 to be replaced twice then the batteries completely died. I still saved them so hopefully can trade in if i get a new body.
My D300 batteries still show zero age in the meter.