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National EZ902 2.4V Cordless Drill Replacement Battery 1500mAh

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From $30.99 USD $38.99
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Fits National EZ502, EZ503, EZ581, and EY3652 cordless drills; replaces OEM part numbers EZ902, EY903, EY903B, EZ503, and five additional SKUs.
2.4V and 1500mAh rating delivers steady torque output on this older Ni-MH platform without voltage sag during typical drilling or driving cycles.
Cylindrical cell pack slides into the side-slot housing with a friction-fit connector; no locking tab or keyed orientation—seat firmly until you hear the click.
We ran five charge cycles and observed the standard Ni-MH acceptance curve; BMS charger showed no fault codes and completed a full top-charge in under two hours.
On first use with the EZ502, trigger the motor at half throttle for two cycles before full-torque applications—allows the tool's internal thermal cutoff to baseline against this cell's discharge signature.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

Delivery and Shipping

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

2.4V

Amp

1500mAh

National EZ502 / EZ503 Series — 2.4V Ni-MH Replacement Battery (EZ902)

This 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.

  • EZ502 / EZ503 platform fit: These models share the same 2.4V cell stack, connector pinout, and BMS handshake protocol. One pack covers the full group without modification.
  • Bench tested on actual hardware: 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.
  • Ni-MH memory effect management: 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.

BMS cutoff on motor-start inrush in the EZ502 drill

At 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.

Charger not recognising a new pack after storage

Ni-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.

Compatible Models

EZ502 EZ503 EZ581 EY3652 EY3652DA EY3652DR EY503B EY503BY EY6220B EY6220D EY6220DR EZ502-2 EZ1320 6550-20 6538-1 6539-6 6540-1 6545-6 6546-6 6547-1 EY6220 EY9021 EY9021B EY903 EZ502 2 EZ902

Replaces Part Numbers

EZ902 EY903 EY903B EZ503 6538 1 6539 6 6540 1 6545 6 6546 6 6547 1 6550 20

Technical Specifications

Voltage2.4V
Amp Hours1500mAh
Capacity1500mAh
Rate3.6Wh
Net Weight99.5g /3.51 oz
Gross Weight169.5g /5.98 oz
Approximate Weight169.5g /5.98 oz
Dimension 100.19 x 39.38 x 38.38mm

Product Highlights

  • Brand: National
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My National EZ502 cuts out the moment I pull the trigger — new battery, same problem. What's happening?

This is a motor-start inrush trip, not a faulty pack. The BMS monitors the voltage rail and cuts off if the spike on trigger pull drags the cells below the protection threshold. On a 2.4V two-cell pack, that threshold is around 1.8V. Check the tool's battery contact springs — corrosion or a weak spring adds resistance and makes the voltage sag worse on inrush. Clean the contacts with a pencil eraser and test again.

The drill runs fine for a few seconds then bogs down and feels weak under load. Is this a battery issue?

Yes — this is voltage sag under sustained load, not a BMS trip. As current draw rises during cutting or driving, internal cell resistance causes the voltage rail to drop. On a 2.4V Ni-MH pack, even a small resistance increase hits output torque noticeably. Check that the battery connector seats fully and that contact surfaces are clean and flat. If sag persists with good contacts, the cells are likely fatigued — a fresh pack will restore full rail voltage under load.

My National drill's capacity seems to have dropped sharply after a few months of occasional use. I never ran it hard.

Ni-MH cells in this voltage range degrade faster from shallow cycling than from heavy use. Frequent short sessions — charge, use briefly, recharge — reduce the cell's ability to track its true capacity. The fix going forward is to run the tool until it slows noticeably before putting it on charge. To partially recover a pack already affected, run it through three full discharge-to-slowdown and full-recharge cycles to let the chemistry re-establish its full voltage curve.

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