The MB-D17 is a Multi-Power Battery Pack for the D500, increasing the number of shots per charge that you can get. It features a Shutter release button and Fn button for ease in vertical shooting.
The MB-D17 can be powered by eight AA batteries or by a single EN-EL 15 or EN-EL 18a Lithium Ion battery.
When using the MB-D17 with eight AA batteries, use the MS-D12 Battery Holder; when using the EN-EL 15 battery to power the MB-D17 use the MS-D12EN Rechargeable Li-ion Battery Holder. The BL-5 Battery Chamber Cover is needed when using the EN-EL 18a to power the MB-D17. The MB-D17 can also be powered via the EH-5b AC power adapter using the EP-5B power connector.