{"product_id":"fakir-robert-ii-replacement-battery-144v-2600mah-li-ion","title":"Fakir Robert II 14.4V Replacement Battery 31 21 140","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eFakir Robert II \/ RS 710 — 14.4V Li-ion Replacement Battery (31 21 140)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 14.4V, 2600mAh Li-ion replacement battery for the Fakir Robert II and RS 710 cordless vacuum cleaners. It replaces OEM part number 31 21 140. Fit the battery, click it into the dock, and the vacuum runs as it did with the original cell.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eRobert II and RS 710 compatibility:\u003c\/strong\u003e\n    Both models run the same 14.4V platform with the same battery bay geometry and BMS handshake. One cell fits both — no adapter, no modification needed.\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 the RS 710 platform. The BMS communicated correctly with the charger, held the voltage rail steady under full suction load, and tripped at the correct low-voltage cutoff without triggering a fault state.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eDock charging on the Robert II:\u003c\/strong\u003e\n    Do not leave this vacuum sitting on the charging dock continuously. Cordless vacuums on permanent dock charge develop capacity fade faster than units charged only when depleted. Charge to full, then remove from the dock.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eSuction dropping before the battery indicator reaches low\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThe Robert II motor draws harder when airflow is restricted — a partially blocked filter forces the motor to pull more current than its rated draw. That sustained overcurrent causes voltage sag on the battery rail, which the BMS reads as a low-cell condition and throttles power before the indicator registers empty. Clean or replace the filter first. If suction recovers and holds, the battery is not the cause.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eMotor cutting out mid-run and then recovering after a short pause\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eThis is a BMS overcurrent trip, not a dead battery. When the motor is working against a sustained blockage or a fully clogged filter, current spikes above the BMS threshold and the cell disconnects to protect itself. After 30–60 seconds the BMS resets, and power returns. Clear the blockage, check the filter, and run the vacuum again. If it cuts out again on an unblocked floor, measure cell voltage — a degraded cell will sag below 12V under load and trigger the same trip.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43428024975450,"sku":"BWCS-RTX682VX-1","price":54.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43428025008218,"sku":"BWCS-RTX682VX-2","price":63.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43428025040986,"sku":"BWCS-RTX682VX-3","price":70.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-RTX682VX-1.webp?v=1779933917","url":"https:\/\/batteryweb.com\/products\/fakir-robert-ii-replacement-battery-144v-2600mah-li-ion","provider":"BatteryWeb","version":"1.0","type":"link"}