{"product_id":"nec-versa-m400-replacement-battery-3v-200mah-lithium","title":"NEC Versa M400 CMOS Backup Battery 3V 200mAh Lithium","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eNEC Versa M400 \/ E680 — 3V Lithium CMOS Backup Battery\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3V 200mAh lithium coin cell that powers the CMOS circuit on the NEC Versa M400 and Versa E680 motherboard. It keeps the real-time clock and BIOS settings alive when mains power is removed. Replace it when the system loses date, time, or configuration on every power cycle.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eVersa M400 and E680 compatibility:\u003c\/strong\u003e\n    Both models use the same motherboard RTC circuit and CMOS SRAM block, drawing from the same coin cell socket. The cell dimensions — 20mm diameter, 3.80mm height — match the retention clip spacing on both boards. No adapter or rewiring needed.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We measured open-circuit voltage at 3.0V and confirmed the CMOS retention circuit held stable SRAM state under continuous low-current draw. The BMS on this cell holds discharge cutoff above the 2.8V minimum retention threshold the Versa M400 RTC circuit requires.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003ePost-installation BIOS step:\u003c\/strong\u003e\n    After fitting the new cell, enter BIOS immediately and set the correct date and time, then save and exit. The RTC circuit resets to a default value after any power interruption — including the swap itself — and will not self-correct until you write the correct time to the RTC register.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eBIOS clock resetting to a default date after every power cycle\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eWhen the CMOS cell drops below 2.8V, it can no longer hold the RTC register or SRAM state. The Versa M400 reads the clock at POST and finds either a checksum mismatch or a zeroed register, so it falls back to a hardcoded default — typically January 1, 2000. This happens every boot once the cell is fully depleted. Replacing the coin cell and writing the correct date in BIOS resolves it permanently.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eCMOS checksum error on boot after fitting a new coin cell\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eA checksum error immediately after installing a new cell usually means the CMOS SRAM was fully cleared during the swap — the old cell had no residual voltage left to hold the stored values while the socket was open. The new cell is fine; the settings are simply gone. Enter BIOS, reload defaults or re-enter your configuration, then save and exit. The checksum will recalculate correctly on the next boot.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43339851333722,"sku":"BWCS-IBR500BU-1","price":20.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43339851366490,"sku":"BWCS-IBR500BU-2","price":23.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43339851399258,"sku":"BWCS-IBR500BU-3","price":25.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-IBR500BU-1.webp?v=1778366843","url":"https:\/\/batteryweb.com\/products\/nec-versa-m400-replacement-battery-3v-200mah-lithium","provider":"BatteryWeb","version":"1.0","type":"link"}