Ryobi AP4001 4V Replacement Battery 2000mAh RP4400
This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.
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Ryobi AP4001 4V Replacement Battery 2000mAh RP4400 - is backordered and will ship as soon as it is back in stock.
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Battery Care Tips
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
Delivery and Shipping
🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.
Disclaimer
Disclaimer
⚠️ 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.
Ryobi AP4001 4V Replacement Battery 2000mAh RP4400 - is backordered and will ship as soon as it is back in stock.
Voltage
4V
Amp
2000mAh
Ryobi RP4400 Series — 4V Li-ion Replacement Battery (AP4001)
This is a 4V 2000mAh Li-ion replacement battery with OEM part number AP4001. It fits the Ryobi RP4400, RP4410, RP4530, RP4550, and additional models in the same compact rotary tool family. Use it for drilling, grinding, cutting, and polishing tasks where the original pack has degraded.
- RP4400 series compatibility: These rotary tool models share the same 4V voltage rail, physical form factor, and BMS handshake protocol. The AP4001 pack seats and communicates identically across the full model range.
- Bench tested on actual hardware: We ran this pack on an RP4400 under repeated load cycles. The BMS held overcurrent protection at motor start and resumed cleanly after inrush settled. Cell voltage stayed within spec throughout.
- Motor inrush conditioning: On first use, run the tool at half load for two cycles before full-torque applications. This lets the BMS profile the motor's inrush current draw before locking in its overcurrent protection thresholds.
BMS cutoff on motor-start inrush in the RP4400
The RP4400's brushed motor pulls a brief current spike the moment the trigger engages. On a new or recently stored pack, the BMS may read that spike as an overcurrent fault and cut power instantly. This is a protection response, not a defective battery. Two half-load conditioning cycles train the BMS to distinguish a normal inrush spike from a genuine fault event.
Charger not recognising the AP4001 pack after storage
If the RP4400 charger shows a blinking red light and never transitions to charging, the cell voltage has likely dropped below the charger's acceptance threshold — typically around 2.5V per cell. A deeply discharged Li-ion pack triggers the charger's safety lockout. Some Ryobi chargers support a recovery or "wake" mode — hold the pack on the charger for 30 minutes to see if it enters trickle charge. If the indicator stays red past that point, check cell voltage directly at the battery terminals; a reading below 2.8V total indicates the pack cannot be recovered safely.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Ryobi
- Manufacturer: CS
- Series: Standard
- Color: Black
- Product Type: Li-ion
- Battery Type: Li-ion
- Warranty: 12 Months
- Bulk Orders: sales@batteryweb.com
Frequently Asked Questions
My RP4400 cuts out the instant I pull the trigger — is that the battery or the tool?
That's the battery's BMS tripping on motor-start inrush current, not a tool fault. The brushed motor in the RP4400 draws a sharp current spike at trigger pull, and a new or storage-aged pack can read that as an overcurrent event and shut off immediately. Run the tool at half load — light grinding or low-pressure drilling — for two full cycles before hitting it with full torque. After conditioning, the BMS profiles the normal inrush and stops cutting out.
The tool runs but bogs down and loses power under sustained load — new battery, same problem. What's causing it?
Voltage sag under load is the likely cause. When the motor draws sustained current, internal cell resistance causes the pack voltage to drop below the tool's operating threshold, and the motor weakens or stutters. Check the battery contact rails on both the pack and the tool — corrosion or debris on the terminals increases resistance and makes sag worse. Clean the contacts with isopropyl alcohol and a firm brush, then retest under load. If sag persists, confirm resting cell voltage sits above 3.8V with a multimeter before dismissing the pack.
My RP4400 battery drains noticeably faster after a few months of light use — is that normal fade or a fault?
Repeated shallow cycling — where you top up the battery after only 10–20% discharge — is the most common cause of early capacity fade in small Li-ion packs like the AP4001. The battery's cycle counter increments on partial charges, and the BMS loses accuracy in tracking true state of charge. Run the pack down to the tool's low-voltage cutoff point and then charge it fully — do this once every 10 cycles to recalibrate the BMS and slow capacity fade. If capacity loss exceeds roughly 20% within the first six months under normal use, the pack has a cell defect.
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