{"product_id":"topcon-111c-replacement-battery-72v-1400mah-ni-cd","title":"Topcon BT-31QB 111C Replacement Battery 7.2V 1400mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eTopcon 111C \/ 101C Series — 7.2V Ni-Cd Replacement Battery (BT-31QB)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 7.2V, 1400mAh Ni-Cd replacement battery for the Topcon 111C, 101C, DL-100, and DL-101C surveying instruments. It fits the same bay as the original BT-31QB and BT-31Q packs. Voltage and capacity match OEM spec exactly — no modifications needed to the instrument.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003e111C and DL-100 series fit:\u003c\/strong\u003e\n    These models share the same 7.2V battery bay, connector pinout, and BMS handshake protocol. One pack covers all listed models without adapter or firmware change.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran this pack through charge and discharge cycles on a Topcon instrument. The BMS accepted the cell chemistry without fault codes, and the low-battery threshold triggered at the correct voltage level.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003ePost-install calibration on first field use:\u003c\/strong\u003e\n    After fitting this pack, run a full calibration cycle through the instrument menu before your first measurement session. The instrument maps battery state during calibration — skipping this step causes premature low-battery warnings that interrupt field measurements even when the pack still has capacity.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eBMS lockout after a Topcon instrument sat unused in its carry case for months\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eNi-Cd cells self-discharge at roughly 1–2% per day at room temperature. A pack stored for three months inside a case can drop below 5.0V total — the point where the BMS enters sleep mode and refuses a standard charge cycle. The instrument will show no response on power-up, and the charger may not register the pack at all. To recover, apply a trickle charge at 100mA until cell voltage climbs above 6.0V, then resume normal charging.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eInstrument shuts off mid-measurement when angle or distance logging is active\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eSustained sensor load during active angle measurement draws more current than standby, and aged or partially discharged Ni-Cd cells develop voltage sag under that load. If the pack voltage dips below the instrument's cutoff threshold — typically around 5.4V under load — the instrument powers off to protect its electronics, even if the display showed adequate charge moments before. This is a cell condition issue, not a firmware fault. Charge the pack fully and retest; if the cutoff repeats at the same point in the measurement cycle, the cells are no longer holding voltage under load and the pack needs replacement.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43360725401690,"sku":"BWCS-TOP111SL-1","price":108.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43360725434458,"sku":"BWCS-TOP111SL-2","price":128.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43360725467226,"sku":"BWCS-TOP111SL-3","price":143.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-TOP111SL-1.webp?v=1778616232","url":"https:\/\/batteryweb.com\/products\/topcon-111c-replacement-battery-72v-1400mah-ni-cd","provider":"BatteryWeb","version":"1.0","type":"link"}