{"product_id":"compaq-511-replacement-battery-108v-4400mah-li-ion","title":"Compaq 511 Replacement Battery 10.8V 4400mAh Li-ion","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eCompaq 511 \/ 611 — 10.8V Li-ion Replacement Battery (HSTNN-IB51)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 10.8V, 4400mAh Li-ion replacement battery for the Compaq 511 and 611 notebooks. It slots into the standard battery bay and connects via the original multi-pin dock connector. OEM part numbers include HSTNN-IB51, HSTNN-IB52, HSTNN-XB51, and 451085-141, among others listed above.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003e511 and 611 shared platform:\u003c\/strong\u003e\n    Both models run the same voltage rail, use the same physical bay dimensions, and share the same BMS handshake protocol — which is why a single cell pack covers both. The connector pinout and charge termination logic are identical across the two.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran this cell through charge and discharge cycles on a 511 unit. The BMS negotiated charge correctly, cell temperature stayed within spec, and the OS fuel gauge registered the full rated capacity after two calibration cycles.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-use discharge cycle on the 511:\u003c\/strong\u003e\n    After installing, run the laptop on battery until it hibernates at cutoff — then charge uninterrupted to 100%. This forces the BIOS to run a learn cycle against the new cell and clears the inaccurate battery health warning that appears after every cell swap.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the 511 shuts down between 20–30% after a battery swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe 511's BIOS tracks cell voltage curves from the previous battery. After a swap, it uses the old voltage map to predict remaining charge — and gets it wrong. Under full CPU and display load, the new cell's actual voltage drops faster than the BIOS expects at that state of charge, triggering an emergency cutoff. Running two full discharge-to-hibernate cycles recalibrates the fuel gauge IC against the new cell chemistry and stops the premature shutdown.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eBIOS reporting battery health as \"poor\" or \"replace\" immediately after fitting a new cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is an EEPROM data mismatch, not a cell defect. The BIOS reads health status from stored cycle count and capacity data written by the previous battery's controller — the new cell arrives with different EEPROM values, which the BIOS flags as degraded. Run the battery learn cycle: discharge fully to hibernate cutoff, then charge to 100% without interruption. After one complete cycle, the BIOS rewrites its health reference and the warning clears.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43410807357530,"sku":"BWCS-HPF550NB-1","price":103.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43410807390298,"sku":"BWCS-HPF550NB-2","price":117.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43410807423066,"sku":"BWCS-HPF550NB-3","price":128.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-HPF550NB-1.webp?v=1779581158","url":"https:\/\/batteryweb.com\/products\/compaq-511-replacement-battery-108v-4400mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}