{"product_id":"sony-ericsson-z800-replacement-battery-37v-900mah-li-ion","title":"Sony Ericsson Z800 BST-33 Replacement Battery 3.7V 900mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eSony Ericsson Z800 Series — 3.7V Li-ion Replacement Battery (BST-33)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 900mAh Li-ion replacement cell for the Sony Ericsson Z800, V800, V800i, and V802, plus over 49 additional compatible handsets sharing the BST-33 form factor. It fits the original battery bay without modification. Use the part number BST-33 to confirm fit before ordering.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eZ800 and V800 series compatibility:\u003c\/strong\u003e\n    These models share the BST-33 footprint, connector pinout, and 3.7V nominal rail. The BMS on each handset communicates with the battery over the same three-pin interface, so one cell covers the full lineup without any adapter or firmware workaround.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled the BST-33 replacement through charge and discharge on a Z800 unit. The BMS accepted the cell without error flags, held voltage flat through mid-discharge, and triggered the low-battery cutoff at the correct threshold rather than dropping unexpectedly under load.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    After installing a new cell, run one full discharge to automatic shutdown before recharging. The Z800's fuel gauge IC was calibrated against the original cell's discharge curve — skipping this step leaves it reading against stale data, which causes erratic percentage jumps for the first several days of use.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Z800 reports wrong battery percentage after a BST-33 cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe Z800 uses a coulomb-counting fuel gauge IC that tracks charge by measuring current in and out of the cell over time. When you swap the physical cell, the IC retains its old baseline — it has no way to know the new cell's actual capacity. The result is percentage readings that lag reality, often showing 100% well before the cell is full or dropping to 15% faster than expected. One complete discharge-to-shutdown followed by a full uninterrupted charge resets the baseline and brings the gauge back into alignment with the new cell.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% on the replacement cell\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a voltage cliff issue, not a capacity problem. Under peak load — screen on, active call, or data transfer — the cell voltage sags momentarily below the BMS cutoff threshold even though the fuel gauge still shows charge remaining. It happens most often on cells that haven't been through a full calibration cycle yet, or on handsets where the charge IC is pushing current into a new high-impedance cell. Run one full cycle first and check that the cell reaches 4.2V at end-of-charge before assuming a fault.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43409468948570,"sku":"BWCS-ERV800SL-1","price":22.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43409468981338,"sku":"BWCS-ERV800SL-2","price":25.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43409469014106,"sku":"BWCS-ERV800SL-3","price":27.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-ERV800SL-1.webp?v=1779579784","url":"https:\/\/batteryweb.com\/products\/sony-ericsson-z800-replacement-battery-37v-900mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}