{"product_id":"sumitomo-type-81c-replacement-battery-111v-4600mah-li-ion","title":"Sumitomo TYPE-81C Survey Replacement Battery 11.1V 4600mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eSumitomo TYPE-81C \/ TYPE-81M12 Series — 11.1V Li-ion Replacement Battery (BU-11)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 11.1V, 4600mAh Li-ion battery replaces the BU-11 and BU-11S packs used in Sumitomo optical surveying instruments. It fits the TYPE-81C, TYPE-81M12, TYPE-Z1C, and T-600C, along with additional models in that lineup. Voltage and capacity match OEM spec so the instrument's power management system reads the pack correctly from first boot.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eTYPE-81C \/ TYPE-81M12 platform compatibility:\u003c\/strong\u003e\n    These models share the same 11.1V three-cell architecture, connector pinout, and BMS communication protocol. One pack covers the full series because the battery authentication handshake is identical across variants.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran the pack through simulated sensor initialisation cycles, logging the BMS response at each probe power-up event. The protection circuit held stable across repeated cold-start current spikes without triggering a low-voltage cutoff.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003ePre-deployment calibration cycle:\u003c\/strong\u003e\n    After fitting this pack, run a full calibration sequence through the instrument's onboard menu before heading to site. The TYPE-81C maps battery state during calibration — skip it and the instrument will throw premature low-battery warnings on the first measurement session, even with a full charge.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the TYPE-81C shuts down mid-measurement with cells still above 10V\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe instrument draws a sustained elevated current when the angle encoder and EDM module run simultaneously during a measurement cycle. If the cell internal resistance has climbed — common in aged packs — voltage sags momentarily below the BMS cutoff threshold even though resting voltage looks acceptable. The protection circuit interprets that sag as a low-cell event and cuts output to protect the cells. A new pack with lower internal resistance holds voltage steady under that combined load, and the shutdowns stop.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eBattery percentage jumping erratically on the display after installing a new pack\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe TYPE-81C estimates charge state against a voltage-to-capacity curve calibrated to the original pack's cell characteristics. A fresh pack with full capacity sits at a slightly different resting voltage than a degraded original, so the indicator recalibrates over the first one to two charge-discharge cycles. Run the instrument to auto-shutoff once, then charge it back to 100% — by the second cycle the displayed percentage will track accurately. If erratic readings persist after two cycles, check that battery contacts are fully seated, as a partial connection causes intermittent voltage readings that confuse the indicator circuit.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43360704233562,"sku":"BWCS-STU810SL-1","price":216.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43360704266330,"sku":"BWCS-STU810SL-2","price":257.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43360704299098,"sku":"BWCS-STU810SL-3","price":288.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-STU810SL-1.webp?v=1778616178","url":"https:\/\/batteryweb.com\/products\/sumitomo-type-81c-replacement-battery-111v-4600mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}