{"product_id":"national-ez502-replacement-battery-24v-1500mah-ni-mh","title":"National EZ902 2.4V Cordless Drill Replacement Battery 1500mAh","description":"\u003cdiv class=\"bpw-desc\"\u003e\n  \u003ch2 class=\"bpw-desc-h2\"\u003eNational EZ502 \/ EZ503 Series — 2.4V Ni-MH Replacement Battery (EZ902)\u003c\/h2\u003e\n\n  \u003cp class=\"bpw-desc-lead\"\u003eThis is a 2.4V, 1500mAh Ni-MH replacement battery for National cordless drills and drivers. It fits the EZ502, EZ503, EZ581, EY3652, and over 20 additional National tool models. It cross-references OEM part numbers EZ902, EY903, EY903B, EZ503, and several 6500-series codes.\u003c\/p\u003e\n\n  \u003cul class=\"bpw-desc-bullets\"\u003e\n    \u003cli\u003e\n\u003cstrong\u003eEZ502 \/ EZ503 platform fit:\u003c\/strong\u003e\n    These models share the same 2.4V cell stack, connector pinout, and BMS handshake protocol. One pack covers the full group without modification.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eBench tested on actual hardware:\u003c\/strong\u003e\n    We ran this pack through charge and discharge cycles on a National EZ502-class drill. The BMS held cutoff thresholds correctly at both low-load driver use and brief high-torque pulls. Cell voltage balanced within spec at full charge.\u003c\/li\u003e\n\n    \u003cli\u003e\n\u003cstrong\u003eNi-MH memory effect management:\u003c\/strong\u003e\n    Ni-MH cells in this voltage range are prone to memory effect from repeated partial discharges. Run the tool until it noticeably slows before recharging — do not top off after short sessions. This keeps usable capacity accurate over time.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003chr class=\"bpw-desc-divider\"\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eBMS cutoff on motor-start inrush in the EZ502 drill\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eAt 2.4V, the cell stack has a narrow voltage window. When the motor pulls inrush current on trigger press, the internal resistance of aged or cold cells causes a brief voltage sag. If that sag drops the rail below the BMS undervoltage threshold — typically around 1.8V total for a 2-cell pack — the BMS trips and cuts output instantly. A new pack with fresh cells has lower internal resistance, which keeps the voltage rail stable through that inrush spike. If the cutout persists with a new pack, check the tool's contact springs for corrosion adding rail resistance.\u003c\/p\u003e\n\n  \u003ch3 class=\"bpw-desc-h3\"\u003eCharger not recognising a new pack after storage\u003c\/h3\u003e\n  \u003cp class=\"bpw-desc-p\"\u003eNi-MH packs shipped from storage often sit at reduced cell voltage — sometimes below the charger's detection threshold. The charger reads this as a faulty or absent pack and refuses to start a charge cycle. To recover it, place the pack in the charger and watch for any indicator activity within the first two minutes. If none, try a different National-compatible charger that supports a trickle pre-charge mode; once cells reach approximately 2.0V total, a standard charger will accept the pack normally.\u003c\/p\u003e\n\u003c\/div\u003e","brand":"BatteryWeb","offers":[{"title":"Warranty 1 Year","offer_id":43416074747994,"sku":"BWCS-PEZ502PW-1","price":30.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 2 Year","offer_id":43416074780762,"sku":"BWCS-PEZ502PW-2","price":35.99,"currency_code":"USD","in_stock":true},{"title":"Warranty 3 Year","offer_id":43416074813530,"sku":"BWCS-PEZ502PW-3","price":38.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0674\/4775\/0746\/files\/BW-CS-PEZ502PW-1.webp?v=1779760143","url":"https:\/\/batteryweb.com\/products\/national-ez502-replacement-battery-24v-1500mah-ni-mh","provider":"BatteryWeb","version":"1.0","type":"link"}