Kenwood KNB-81L is the spare or replacement Lithium Ion IP67 rated battery for the ProTalk NEXEDGE NXP500 series radios. This battery is 2200 mAh and last 15 hours on average.
Amazon.com: 3400mAh Battery Replacement for FC8810 FC8820 FC8830 FC8832 4ICR19/65 : Health & Household