{"product_id":"amazon-pw3840-replacement-battery-37v-3350mah-li-ion","title":"Amazon Echo 1st Gen Replacement Battery 3.7V 3350mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eAmazon Echo Tap — 3.7V Li-ion Replacement Battery (58-000138)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis 3.7V, 3350mAh Li-ion cell replaces the original battery in the Amazon Echo Tap (PW3840, PW3840KL). It matches the OEM part number 58-000138 and fits the Tap's battery bay without modification. Capacity figure is taken directly from the product specification — 12.4Wh total energy.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003ePW3840 and PW3840KL platform:\u003c\/strong\u003e\n    Both model variants run the same 3.7V single-cell architecture with an identical connector and BMS handshake. One battery covers both, because Amazon used the same power rail and protection circuit across the full Tap production run.\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 Tap unit, confirmed BMS communication cleared without error flags, and verified the fuel gauge reported accurately across the full state-of-charge range.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eFuel gauge calibration on the Tap:\u003c\/strong\u003e\n    The Tap's onboard fuel gauge drifts when the cell is never allowed to discharge below 30%. Once a month, run the speaker down past the low-battery warning before plugging in — this lets the BMS recalibrate the full capacity window and keeps the indicator accurate.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eAudio distorting before the battery indicator reaches empty on the Echo Tap\u003c\/h3\u003e\n\n  \u003cp class=\"bpw-desc-p\"\u003eThe Tap's amplifier draws a short, high-current spike each time bass frequencies hit. As the cell ages and internal resistance climbs, that spike causes a voltage sag the BMS cannot mask — the amp clips before the fuel gauge has caught up with actual cell state. You hear crackling or thinning audio while the indicator still shows two bars. A fresh cell with low internal resistance eliminates the sag and restores clean output. If distortion persists after fitting a new battery, check that the speaker grille is not blocked — thermal load on the amp compounds the issue.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eEcho Tap not waking from USB after sitting unused for weeks\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eA Tap left uncharged for several weeks can drop below the minimum acceptance voltage the charging IC requires to initiate a charge cycle — typically under 2.5V for this cell chemistry. The device appears completely dead and does not respond to the USB cable. The fix is a trickle pre-charge: leave the USB cable connected for 20–30 minutes without expecting any screen or LED response, then check for the charging indicator. If the cell has self-discharged below 2.0V, the BMS may have latched into deep-discharge lockout and the cell will need replacement rather than recovery.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43416232067162,"sku":"BWCS-AMP840XL-1","price":29.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43416232099930,"sku":"BWCS-AMP840XL-2","price":33.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43416232132698,"sku":"BWCS-AMP840XL-3","price":36.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-AMP840XL-1.webp?v=1779761042","url":"https:\/\/batteryweb.com\/products\/amazon-pw3840-replacement-battery-37v-3350mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}