{"product_id":"panasonic-cf-r4-series-replacement-battery-74v-7800mah-li-ion","title":"Panasonic CF-VZSU42 Laptop Replacement Battery 7.4V 7800mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003ePanasonic CF-R4 Series — 7.4V Li-ion Replacement Battery (CF-VZSU42)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 7.4V 7800mAh (57.72Wh) Li-ion battery replaces OEM part CF-VZSU42 and CF-VZSU42U in the Panasonic Toughbook CF-R4 ultraportable series. It fits the CF-R4GC5AXS, CF-R4GW5AXR, CF-R4GW5AXS, and related CF-R4 variants. Cell count, connector pinout, and BMS communication protocol match the original factory specification.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eCF-R4 series compatibility:\u003c\/strong\u003e\n    All CF-R4 variants share the same 7.4V two-cell architecture, battery bay dimensions, and SMBus BMS handshake — so one cell works across the full model range without modification.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran this cell on a CF-R4 unit and confirmed the BMS negotiated correctly at first insertion, charge acceptance started at the expected 8.0V threshold, and the BIOS recognised the pack without throwing an unknown-battery error.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFirst-cycle conditioning on the CF-R4:\u003c\/strong\u003e\n    After installing, run the laptop on battery until it shuts down at hibernate-cutoff, then charge uninterrupted to 100%. The CF-R4 BIOS runs a battery learn cycle on this sequence — skipping it leaves the fuel gauge reading EEPROM data from the old cell, which causes the health warning to persist.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the CF-R4 BIOS shows \"Battery exhausted\" or poor health after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe CF-R4 stores battery health data in EEPROM on the pack itself. When you fit a new cell, the BIOS reads that fresh EEPROM and flags a mismatch against its stored cycle history — this shows up as a poor-health or \"battery exhausted\" warning even on a brand-new cell. The fix is a full discharge-to-hibernate followed by an uninterrupted full charge. That sequence triggers the BIOS learn cycle, which rewrites the reference data against the new cell's actual capacity. After two to three complete cycles the health indicator normalises and the warning clears.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eLaptop shuts off at 20–30% charge shown on the CF-R4\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a voltage-cliff failure on an aged original cell, not a fault with a replacement. Under combined CPU and display load, the degraded cell cannot hold voltage above the BMS low-voltage cutoff threshold — the system shuts down before the OS fuel gauge reaches 0%. A replacement cell at full capacity sustains voltage through that load spike. After fitting the new cell, run the full discharge-and-recharge learn cycle so the fuel gauge IC recalibrates its voltage-to-percentage curve against the new chemistry. The cutoff threshold is 6.0V across the two-cell pack.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43410828001370,"sku":"BWCS-CFR4NB-1","price":109.99,"currency_code":"USD","in_stock":false},{"title":"Warranty 2 Year","offer_id":43410828034138,"sku":"BWCS-CFR4NB-2","price":128.99,"currency_code":"USD","in_stock":false},{"title":"Warranty 3 Year","offer_id":43410828066906,"sku":"BWCS-CFR4NB-3","price":143.99,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-CFR4NB-big.webp?v=1779581286","url":"https:\/\/batteryweb.com\/products\/panasonic-cf-r4-series-replacement-battery-74v-7800mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}