#1
★ Top Pick
Mighty Max Battery YTX9-BS -12 Volt 8 AH, 135 CCA, Rechargeable Maintenance Free SLA AGM Motorcycle Battery
The Mighty Max YTX9-BS matches the KTM 390 Duke's factory battery specification exactly — the YTX9-BS is the OEM-designated group size for this bike, so fitment in the compact under-seat tray is straightforward with no adapter needed. The 135 CCA rating handles the 373cc single-cylinder's cold-start demands reliably, and the sealed AGM construction means no maintenance between rides. Caveat: longevity reports are mixed, so keep a tender on it during storage months.
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