{"product_id":"righton-retinomax-3-replacement-battery-74v-2600mah-li-ion","title":"Righton RT-121 Retinomax 3 Replacement Battery 7.4V 2600mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eRighton Retinomax 3 \/ K-Plus 3 — 7.4V Li-ion Replacement Battery (RT-121)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 7.4V, 2600mAh Li-ion replacement for the Righton Retinomax 3 and K-Plus 3 portable autorefractors. These handheld clinical refractors require a stable power supply throughout examination sequences — a degraded cell causes mid-test shutdowns and inaccurate readings. The RT-121 matches the OEM voltage, capacity, and connector configuration for both models.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eRetinomax 3 and K-Plus 3 platform:\u003c\/strong\u003e\n    Both devices run on the same 7.4V battery rail and share the RT-121 connector and BMS handshake protocol. A cell that doesn't meet the BMS handshake spec will trigger a low-battery fault even at full charge.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through the Retinomax boot sequence and full charge-discharge under clinical load. The BMS accepted the cell without fault codes after one full conditioning cycle.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-use self-test protocol:\u003c\/strong\u003e\n    After installation, allow the device to complete its full power-on self-test without interruption. The Retinomax BMS runs a verification sweep at startup — cutting power during this sequence stores a false battery fault that persists until the next clean reboot.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Retinomax 3 alarms low battery with a freshly charged replacement installed\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe Retinomax BMS compares the new cell's discharge curve against stored OEM thresholds from the first startup. A brand-new cell hasn't built its internal resistance profile yet, so the BMS reads the chemistry signature as uncertain and flags it. This isn't a fault with the replacement — it's the BMS applying a conservative safety threshold. Running one complete charge-discharge cycle lets the BMS learn the cell and clear the alarm. After that cycle, the device should accept the battery without fault.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eRetinomax 3 won't power on after the replacement cell sat in storage\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eLi-ion cells self-discharge during storage. If the RT-121 cell dropped below approximately 2.5V per cell (5.0V pack total), the BMS enters deep-discharge lockout and blocks power delivery to prevent cell damage. The device will appear completely dead — no startup chime, no screen. Place the battery on charge and leave it for a minimum of two hours before attempting to power on; the charge IC needs time to bring the cell up through the recovery threshold before the BMS re-enables output. If the charger shows no activity after 30 minutes, reseat the battery in the charger to reinitiate the recovery sequence.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43381444968538,"sku":"BWCS-RTK300MD-1","price":35.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43381445001306,"sku":"BWCS-RTK300MD-2","price":41.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43381445034074,"sku":"BWCS-RTK300MD-3","price":45.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-RTK300MD-1.webp?v=1778900853","url":"https:\/\/batteryweb.com\/products\/righton-retinomax-3-replacement-battery-74v-2600mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}