{"product_id":"sony-cmd-z7-replacement-battery-37v-600mah-li-ion","title":"Sony CMD-Z7 Replacement Battery QN-Z7BPS 3.7V 600mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eSony CMD-Z7 — 3.7V Li-ion Replacement Battery (QN-Z7BPS)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V 600mAh Li-ion replacement for the QN-Z7BPS battery that powers the Sony CMD-Z7 smartphone. The CMD-Z7 is an early 2000s handset — original batteries from this era are long out of production and degrade significantly over two decades. This cell restores the device to functional operating capacity.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eCMD-Z7 fit:\u003c\/strong\u003e\n    The CMD-Z7 uses a single-cell Li-ion pack with a dedicated connector and BMS handshake tied to Sony's charge management circuit. The QN-Z7BPS is the only part number that satisfies this handshake — substitute cells without the correct ID resistor will be rejected by the charge IC.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through charge and discharge on a CMD-Z7 board. The BMS accepted the cell on first contact, charge termination triggered correctly at 4.2V, and the protection circuit tripped as expected under an overcurrent event.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    After installation, run one complete discharge down to automatic shutoff, then charge uninterrupted to 100% before daily use. The CMD-Z7's fuel gauge IC was calibrated to the original cell's discharge curve — skipping this cycle leaves the coulomb counter working off stale data, which causes erratic percentage readings from day one.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the CMD-Z7 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe CMD-Z7 uses a fuel gauge IC that tracks charge state by counting coulombs against a stored discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual cell chemistry and internal resistance. The result is percentage readings that bear little relation to real charge state — the phone may show 60% and shut down, or show 10% and keep running. One full discharge-to-shutoff followed by a complete uninterrupted charge resets the coulomb counter and lets the IC relearn the new curve.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eCMD-Z7 shutting down suddenly at 20–30% remaining\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a voltage cliff issue, not a capacity problem. Aged or freshly installed cells with slightly higher internal resistance drop below the BMS cutoff threshold when the processor or display pulls a load spike — even though the fuel gauge still reads 20–30%. The cell voltage collapses faster than the coulomb counter can update. To confirm, charge to 100%, let the phone sit idle until it shuts off, then check the resting cell voltage immediately — a reading below 3.2V under no load confirms the cell is not holding voltage under load and the replacement cycle should be repeated with a verified cell.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43409469407322,"sku":"BWCS-SOZ7SL-1","price":22.99,"currency_code":"USD","in_stock":false},{"title":"Warranty 2 Year","offer_id":43409469440090,"sku":"BWCS-SOZ7SL-2","price":25.99,"currency_code":"USD","in_stock":false},{"title":"Warranty 3 Year","offer_id":43409469472858,"sku":"BWCS-SOZ7SL-3","price":27.99,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-SOZ7SL-big.webp?v=1779579784","url":"https:\/\/batteryweb.com\/products\/sony-cmd-z7-replacement-battery-37v-600mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}