2-Pack 21700 Rechargeable Battery, 4000mAh 3.6V Flat Top, High Drain 40A for Flashlights, Headlamps Devices & High-Power Applications
Description
Key Features
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40A Continuous High Drain – Handles extreme current loads without dangerous voltage sag.
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4000mAh Verified Capacity – Real tested capacity; ideal balance of runtime and power.
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Flat Top Design – Low contact resistance, fits most 21700-compatible devices.
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Low Internal Resistance (~12-15mΩ) – Less heat, more efficient energy transfer.
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A-Grade Cells – Capacity-matched and inspected, no recycled junk.
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2-Pack Convenience – Two cells ready to rotate or use in dual-battery setups.
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Long Cycle Life – 500+ charge cycles with ≥70% capacity retention.
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Built-in Safety – Pressure relief vent and CID for critical fault protection.
Parameters
| Parameter | Specification |
|---|---|
| Model | 21700 Flat Top Li-ion |
| Nominal Capacity | 4000mAh |
| Nominal Voltage | 3.6V |
| Full Charge Voltage | 4.2V |
| Cut-off Voltage | 2.5V |
| Max Continuous Discharge | 40A |
| Internal Resistance | ~12–15mΩ (AC 1kHz) |
| Chemistry | INR/NMC |
| Protection | None (unprotected flat top) |
| Dimensions | 21.0mm x 70.0mm |
| Weight | Approx. |
| 68g | Cycle Life | ≥500 cycles | Charging Current | Standard 1.5A, rapid 4A (monitor temperature) |
Applications
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High-Lumen Flashlights – Sustains turbo mode for tactical, search, and EDC torches.
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Headlamps – Powers high-output caving, cycling, and rescue headlamps.
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Power Tools – Rebuild cordless drill and impact wrench packs needing 40A surges.
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DIY Projects – Use in custom power banks, portable amps, or small e-mobility packs.
FAQ
Q: Are these protected batteries?
A: No. They are unprotected flat-top cells for maximum discharge performance. Use only in devices with low-voltage cutoff or add an external protection circuit. Never short circuit.
Q: Will they fit my flashlight?
A: If your flashlight accepts unprotected flat-top 21700 cells, yes. Check that the positive contact can reach a flat terminal. Devices designed for button tops may need a magnet spacer (use with caution).
Q: What charger is required?
A: A Li-ion charger supporting 3.6V/3.7V cells, 21700 size, with CC/CV and 4.2V cutoff. Recommended brands: Xtar, Nitecore, Gyrfalcon. Do not use NiMH chargers.
Q: Is the 4000mAh real?
A: Yes, tested at 0.2C discharge. At high currents (e.g., 20A), usable capacity is slightly lower (~3800-3900mAh), which is normal.
Q: Can I mix with other cells?
A: Never mix old and new cells or different models in series. Always use identical, age-matched batteries.
Shipping and Returns
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Free Shipping: Enjoy free shipping on all orders over $65. For orders under $65, the shipping cost is $8.99.
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Delivery Time: Once shipped, orders typically arrive within 7–15 business days.
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Easy Returns: We want you to be completely satisfied. If you're not, you can return your product within 30 days of receiving your order. Please ensure the items are unused and in their original condition. For return instructions, please contact our support team.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
Security
Capacity tested 3950mAh and 3980mAh, close to 4000. They handle 40A bursts well. The wrap is a bit thin, but no big deal.
They work as advertised, 40A continuous no problem. Capacity is near 4000mAh. However, cheaper alternatives exist. Still happy.
Installed in a direct-drive FET flashlight pulling ~35A, these 21700s hold voltage above 3.5V for most of the discharge. No step-down needed. True 4000mAh.
No connection issues in my Sofirn and Wurkkos lights. At 40A, these provide stable output. I'm ordering another set.
Both cells had identical IR and voltage. Put them in series for a 2S boat, 30A draw, runs cool. Punchy performance.
Refund Policy
OneAndes Return & Refund Policy
At OneAndes, we are committed to providing high-quality cylindrical lithium-ion batteries for your drones, vacuums, garden tools, and other power needs. If you are not completely satisfied with your purchase, we are here to help. Please read our full return policy below before initiating a return.
1. Return Window
You have 30 calendar days from the date you received your item(s) to request a return. Any return request submitted after 30 days will not be eligible for a refund or exchange.
2. Eligibility Conditions
To qualify for a return, all items must meet the following conditions:
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Condition: Items must be unused, undamaged, and in the same condition that you received them.
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Packaging: Items must be returned in their original packaging with all accessories, manuals, and protective covers intact.
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Proof of Purchase: A valid receipt, order confirmation email, or proof of purchase must accompany all returns.
Non-Returnable Items:
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Batteries that have been installed, used, or show any signs of wear.
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Items marked as “Final Sale” or “Clearance” at the time of purchase.
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Customized or special-order products.
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Gift cards.
If a returned item fails to meet these conditions, we reserve the right to deny the return or charge a restocking fee.
3. How to Initiate a Return
Follow these steps to return your product:
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Contact Us: Email our support team at support@oneandes.com with your order number and the reason for return. We aim to respond to all return requests within 24 hours on business days.
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Receive RMA: We will provide you with a Return Merchandise Authorization (RMA) number and return instructions. Do not ship any item without an RMA number.
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Pack Securely: Place the item in its original packaging, include all accessories, and clearly write the RMA number on the outside of the box.
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Ship to Our US Warehouse: Ship the package to the following address:
OneAndes Returns
10320 6th St
Rancho Cucamonga, CA 91730
USA*Important: Lithium-ion batteries are classified as hazardous materials (Class 9). Please follow the shipping guidelines provided in Section 4 below. We recommend using a trackable shipping service and purchasing shipping insurance, as we cannot guarantee receipt of your returned item.*
4. Return Shipping Costs
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Defective or Incorrect Items: If the item you received is defective, damaged in transit, or different from what you ordered, OneAndes will cover the return shipping cost. In this case, we will provide you with a prepaid return shipping label.
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Buyer’s Remorse / Non-Defective Returns: If you are returning an item for any other reason (e.g., no longer needed, ordered the wrong model), you are responsible for the return shipping costs. You must prepay the return shipping cost using a trackable carrier that accepts lithium batteries. We do not provide prepaid return labels for non-defective returns.
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Lithium Battery Shipping Regulations: By law, all returns must be shipped in compliance with applicable dangerous goods regulations. We will provide guidance on proper packaging and labeling. Failure to comply may result in carrier refusal, seizure, or additional fees. We are not responsible for returned items lost or rejected by the carrier due to improper shipping.
5. Refunds
Once we receive and inspect your return at our Rancho Cucamonga, CA facility, we will notify you via email of the approval or rejection of your refund.
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Approved Refunds: If approved, your refund will be processed to your original method of payment within 5 to 10 business days. Please note that depending on your bank or credit card issuer, it may take additional time for the credit to appear on your statement.
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Partial Refunds: In certain situations, only partial refunds may be granted:
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Items not in original condition, missing parts, or damaged for reasons not due to our error.
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Items returned more than 30 days after delivery (reviewed on a case-by-case basis).
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Non-Refundable Fees: Original shipping charges are non-refundable unless the return is due to our error (defective product or incorrect shipment).
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Restocking Fee: We do not charge a restocking fee for defect-free returns, but we may deduct the return shipping cost, which will be deducted from your refund.
6. Exchanges
We replace items only if they are defective or damaged upon arrival. If you need to exchange a defective item for the same product, please contact us at support@oneandes.com. Exchanges are subject to product availability.
If you ordered the wrong battery size or model, please follow the standard return process above and place a new order for the correct item.
7. Damaged or Missing Items
If your package arrives visibly damaged, please take photos of the package before opening and contact us immediately. We will work with the shipping carrier to file a claim and arrange for a replacement or refund. Damaged or missing item claims must be reported within 7 calendar days of delivery. For immediate assistance, you may also call us at (213) 316-8849.
8. Order Cancellation
You may cancel your order without penalty if it has not yet been shipped. To cancel, email us at support@oneandes.com as soon as possible. If the order has already been processed or shipped, you will need to follow the standard return process upon receipt.
9. Warranty
All OneAndes batteries are backed by a 12-month limited warranty against defects in materials and workmanship. This warranty does not cover damage caused by misuse, improper charging, unauthorized modifications, normal wear and tear, or use outside of manufacturer specifications. For warranty claims, please contact our support team.
10. Contact Us
If you have any questions about our Return & Refund Policy, please reach out:
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Email: support@oneandes.com
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Phone: (213) 316-8849 (Mon-Fri, 9 AM – 5 PM Pacific Time)
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Mailing Address: 10320 6th St, Rancho Cucamonga, CA 91730, USA
We aim to respond to all inquiries within 24 hours during business days. Please include your order number for faster assistance.