{"product_id":"t-mobile-sidekick-2-replacement-battery-37v-1200mah-li-polymer","title":"T-Mobile Sidekick 2 Replacement Battery IA3Y701C2 3.7V 1200mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eT-Mobile Sidekick 2 — 3.7V Li-Polymer Replacement Battery (IA3Y701C2)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 3.7V, 1200mAh lithium-polymer replacement battery for the T-Mobile Sidekick 2 (Sidekick II). It matches the OEM part number IA3Y701C2 and fits directly into the original battery bay. The cell powers the display, processor, and wireless radio just as the factory unit did.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eSidekick 2 \/ Sidekick II fit:\u003c\/strong\u003e\n    Both the Sidekick 2 and Sidekick II use the same IA3Y701C2 cell — same voltage rail, same physical connector, and the same BMS handshake with the device's charge IC. No modifications needed.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We cycled this cell through a full charge-discharge sequence and monitored the BMS cutoff response under simulated screen and radio load. The protection circuit held within expected voltage thresholds throughout.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge recalibration on first use:\u003c\/strong\u003e\n    On first installation, run one full discharge down to automatic shutoff, then charge uninterrupted to 100%. This gives the Sidekick's fuel gauge IC a clean reference curve against the new cell before resuming normal 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 Sidekick 2 reports wrong battery percentage after a cell swap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe Sidekick 2 uses a fuel gauge IC that builds its percentage readings from a stored discharge curve calibrated to the original cell. When a new cell goes in, that stored curve no longer matches actual cell chemistry — so the IC reads capacity against the wrong baseline. The result is a percentage that jumps, stalls, or drops suddenly even when the cell has charge left. One full discharge-to-shutoff cycle followed by a full uninterrupted charge resets the coulomb counter and restores accurate readings.\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 happens when the cell voltage drops sharply under combined screen and modem load — a voltage cliff the fuel gauge hasn't mapped yet. The device reads 25% remaining but the actual cell voltage has already fallen below the BMS cutoff threshold, typically around 3.0V, triggering an immediate shutdown. It is not a defective cell — it is an uncalibrated fuel gauge IC reading a new discharge curve as if it were the old one. Complete one full discharge cycle and the shutoffs will stop occurring at that percentage range.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43405149634650,"sku":"BWCS-SK2SL-1","price":24.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43405149667418,"sku":"BWCS-SK2SL-2","price":27.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43405149700186,"sku":"BWCS-SK2SL-3","price":30.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-SK2SL-1.webp?v=1779370298","url":"https:\/\/batteryweb.com\/products\/t-mobile-sidekick-2-replacement-battery-37v-1200mah-li-polymer","provider":"BatteryWeb","version":"1.0","type":"link"}