{"product_id":"novipro-ul521-replacement-battery-24v-3500mah-ni-mh","title":"Novipro 880BAT UL521 Survey Replacement Battery 2.4V 3500mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eNovipro UL521 \/ LS521 Series — 2.4V Ni-MH Replacement Battery (880BAT)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 2.4V, 3500mAh Ni-MH replacement battery for the Novipro UL521, UL522, LS521, and LS522 surveying and test instruments. It matches the OEM part numbers 880BAT and 3000BAT. Capacity figure comes from the product data — 8.4Wh total energy.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eUL521 \/ UL522 \/ LS521 \/ LS522 compatibility:\u003c\/strong\u003e\n    These four models share the same 2.4V battery bay, connector pinout, and BMS handshake protocol. Swapping the pack across any of them requires no adapter or firmware change — the instrument reads the cell voltage directly.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this pack through the UL521's charge circuit and monitored the BMS response during sensor initialisation. The cell held voltage within tolerance through probe power-up spikes and sustained logging draws without triggering a cutoff event.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-cycle calibration on the UL521:\u003c\/strong\u003e\n    After fitting the new pack, run a full calibration cycle through the instrument's menu before field deployment. The UL521 maps battery state during calibration — skipping this step causes the low-battery indicator to trip early on the first measurement session, even with a fully charged cell.\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 the UL521 sat unused in a carry case for months\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eNi-MH cells self-discharge over storage. If the pack sits long enough, cell voltage drops below the BMS recovery threshold — typically around 1.0V per cell on a 2-cell 2.4V pack. At that point the BMS enters a protective sleep state and the instrument shows no charge activity or a blank screen when connected to the charger. The fix is a slow-rate recovery charge using a compatible Ni-MH charger set to trickle mode, not the fast-charge circuit. Once the cells recover above approximately 2.0V combined, the BMS re-initialises and normal charging resumes.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eReadings resetting or drifting mid-session during continuous logging\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eSustained sensor load draws more current than standby operation — on the UL521 this can pull the cell voltage down enough to cause a momentary dropout without fully shutting the instrument off. That dropout resets the active measurement register, which appears as a mid-session reading jump or data gap in the log. The cause is gradual capacity fade in an aged cell, not a firmware issue. Replace the pack and verify the cell rests above 2.3V after a full charge before heading into the field.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43360659865690,"sku":"BWCS-RBX880SL-1","price":33.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43360659898458,"sku":"BWCS-RBX880SL-2","price":38.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43360659931226,"sku":"BWCS-RBX880SL-3","price":42.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-RBX880SL-1.webp?v=1778616161","url":"https:\/\/batteryweb.com\/products\/novipro-ul521-replacement-battery-24v-3500mah-ni-mh","provider":"BatteryWeb","version":"1.0","type":"link"}