Battery tray that lets the PI-4100 run on standard single-use AA batteries.Potomac LM10540 AA Battery Tray for PI-4100SKU: LM10540 $28.00 Regular Price$27.05Sale PriceExcluding Sales Tax | Shipping PolicyQuantity*Add to CartBrandPotomac InstrumentsProduct DetailsManufacturer: Potomac InstrumentsManufacturer part number: LM10540Sold by: Radio Gearheads, 705 Eaton Ave N, Fosston, MN 56542 Questions about compatibility, configuration or lead time? Call 1-800-992-1506 or use Get A Quote.