{"product_id":"lenovo-a5-replacement-battery-385v-3900mah-li-polymer","title":"Lenovo A5 BL291 Replacement Battery 3.85V 3900mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eLenovo A5 \/ L18021 — 3.85V Li-Polymer Replacement Battery (BL291)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.85V, 3900mAh Li-Polymer cell replaces the original BL291 battery in the Lenovo A5 (model L18021) smartphone. It fits the stock battery bay without modification and connects via the original ribbon connector. Capacity figures come directly from our sourced cell spec — 3900mAh at 15.02Wh.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eA5 and L18021 compatibility:\u003c\/strong\u003e\n    Both model numbers refer to the same physical handset sold across different regional markets. The battery bay dimensions, connector pinout, and BMS communication protocol are identical — one cell fits both.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through full charge and discharge on an A5 unit. The BMS accepted the charge IC handshake without error flags, and the protection circuit tripped correctly at the low-voltage cutoff threshold.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before higher charge rates are introduced.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eWhy the Lenovo A5 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe A5 uses a fuel gauge IC that builds its battery model from accumulated charge and discharge data on the original cell. When a new cell goes in, the IC still holds the old cell's impedance and capacity curve in memory. This mismatch causes the reported percentage to drift from the actual state of charge — sometimes by 10–15 points. One full discharge down to automatic shutdown followed by an uninterrupted charge to 100% forces the coulomb counter to reset and relearn against the new cell. After that cycle, percentage reporting stabilises.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSudden shutdown at 20–30% on the replacement cell\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThis happens when the cell voltage drops below what the modem or display load demands, even though the reported percentage looks healthy. A fresh Li-Polymer cell has a steeper voltage cliff under high-current draw until it has been broken in through a few charge cycles. The phone's protection circuit interprets that voltage sag as a critically low cell and cuts power immediately. Run two to three full discharge-charge cycles — after that, the cell's internal resistance stabilises and the voltage cliff flattens. If shutdowns persist past cycle three, check that the battery connector ribbon is fully seated and making clean contact at all four pins.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43391992660058,"sku":"BWCS-LVA500SL-1","price":26.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43391992692826,"sku":"BWCS-LVA500SL-2","price":29.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43391992725594,"sku":"BWCS-LVA500SL-3","price":32.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-LVA500SL-1.webp?v=1779142762","url":"https:\/\/batteryweb.com\/products\/lenovo-a5-replacement-battery-385v-3900mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}