Welcome to our store. Your trusted source for batteries and power solutions. Learn more

For support or quotes: sales@batteryweb.com
WELCOME5
BatteryWeb

Sager NP9870-S Compatible Battery 15.12V 5800mAh Li-ion

Up to 19% off
New arrival
From $98.99 USD $121.99
Shipping calculated at checkout.
Fits Sager NP9870-S and NP9870 laptops, replaces original battery pack.
15.12V and 5800mAh capacity delivers 87.7Wh to sustain CPU and display load together.
Connector seats straight into the internal slot with a locking tab on the left side.
We tested on a fresh NP9870-S — BMS accepted the cell without fault codes, voltage held steady under sustained load.
After installation, discharge fully to hibernation shutdown then charge uninterrupted to 100% — this resets the BIOS battery learn cycle and clears the inaccurate health warning that appears after every cell swap.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
WECARE5
Visa Mastercard American Express PayPal Apple Pay Google Pay Shop Pay Discover Klarna Afterpay Stripe
✦

Check that your old battery model number and device model to match our description. This makes sure they work together.

✦

We ship your order same day if you buy it before 4 PM EST.

Warranty

Let customers speak for us

from 11 reviews

Product is exactly as described and arrived quickly

Robert Jones
Rocket ES4-12 Compatible Replacement Battery

It took a bit longer than expected, likely due to the holiday season, but that was understandable. So far, the battery seems to be working well!

Linda M.
MGE UPS Systems Pulsar EX 1500RT Compatible Replacement Battery By Bright Way

Excellent substitute for the original, appearing to be the perfect replacement.

Alberto J.
APC SMART-UPS RT SURTA3000RMXL3U UPS High Performance Replacement Battery Set

It was what i was looking for. Support is fast

Jaswal
WAHEGURUG - RADHASWAMI

Fast service

Mark Casias
BatteryWeb

Perfect fit

Mark Casias
STX20L-BS Battery for Harley Softail FLS FLST 1991-2017 High Performance

Works Perfectly!!

Ben Benson
Invacare 220 Scooter High Performance Medical Replacement Battery Set

Send Your Battery Photo

Expert Technician Help

Snap a photo or video of your battery and send it to us. We'll identify the exact replacement—fast and hassle-free. Our team has helped thousands of customers find the right battery quickly and easily.

POST YOUR BATTERY IMAGE
Product & Solutions Expert

Product & Solutions Expert

✉ sales@batteryweb.com

🔹 10+ Years Battery Experience 🔹 Fast & Accurate Identification

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

🔹 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: 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

15.12V

Amp

5800mAh

Sager NP9870-S / NP9870 — 15.12V Li-ion Replacement Battery

This is a 15.12V, 5800mAh (87.7Wh) Li-ion replacement battery for the Sager NP9870-S and NP9870 gaming laptops. It restores unplugged operation when the original cell has degraded or failed. Dimensions are 156.20 × 95.60 × 19.20mm — confirm clearance before ordering if your chassis has been modified.

  • NP9870-S and NP9870 compatibility: Both models share the same 15.12V battery rail, connector pinout, and BMS handshake protocol — one cell fits both without adapter or firmware difference.
  • Bench tested on actual hardware: We cycled this cell through charge, discharge, and CPU-plus-display load scenarios. The BMS held voltage within spec under sustained gaming load and triggered protection cutoff correctly at the low-cell threshold.
  • First-cycle calibration after install: After fitting this battery, run the laptop down to hibernate cutoff under normal load, then charge uninterrupted to 100%. This forces the BIOS battery learn cycle to reset against the new cell's actual capacity and clears the inaccurate health warning that appears after every cell swap.

BIOS reporting poor battery health immediately after swap

The NP9870's BIOS reads health data stored in the old cell's EEPROM and compares it against the new cell on first boot. The new cell has no discharge history, so the BIOS flags it as unknown or degraded. This is not a fault with the replacement cell. Run one full discharge-to-hibernate then a full uninterrupted charge — after two to three cycles the BIOS recalibrates and the health indicator returns to normal.

Laptop shuts down at 20–30% charge remaining

This happens when the fuel gauge IC hasn't yet mapped the new cell's actual voltage curve. Under full CPU and display load, the system draws enough current to expose a voltage cliff that the uncalibrated gauge didn't predict — the BMS trips before the OS can respond. The fix is calibration: discharge fully to hibernate under load, not idle. After two full cycles the gauge IC tracks the new cell accurately and unexpected shutdowns stop. Confirm the cutoff voltage reads at or above 11.4V during the next discharge using your system's battery diagnostics.

Compatible Models

NP9870-S NP9870

Technical Specifications

Voltage15.12V
Amp Hours5800mAh
Capacity5800mAh
Rate87.7Wh
Net Weight415.4g /14.65 oz
Gross Weight565.4g /19.94 oz
Approximate Weight565.4g /19.94 oz
Dimension 156.20 x 95.60 x 19.20mm

Product Highlights

  • Brand: Sager
  • 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 NP9870-S just shows 0% and won't charge after I fitted the new battery — is the cell dead?

No — this is the BIOS failing to read the new cell's EEPROM data on first boot. The original cell left charge history the firmware expected; the replacement starts blank. Power off, reseat the battery connector firmly, then boot and let the system sit on charge for 20 minutes before checking again. If the gauge still reads 0%, trigger the BIOS battery learn cycle by discharging to hibernate then charging uninterrupted to 100%.

The system info panel shows the wrong Wh rating — it says something different from the 87.7Wh on the listing.

The Wh figure shown in Windows or the BIOS is pulled from the cell's EEPROM, which stores the rated capacity from the original manufacturer's firmware — not a live measurement. The actual chemistry in the replacement cell delivers 87.7Wh; the displayed number reflects whatever value was written to the chip during cell production. Run two full calibration cycles and the reported figure will converge closer to actual capacity as the fuel gauge IC builds its own measurement history.

Charging stops at around 80% and refuses to go higher — is something wrong with the charger or the battery?

This is almost always a BIOS-controlled charge limit, not a battery fault. Many Sager gaming laptops include a battery care mode that caps charging at 80% to reduce cell stress during extended desk use. Check your power management software or BIOS settings under "Battery Charge Threshold" or equivalent and disable the limit. Once the cap is off, charge to 100% — the replacement cell at 15.12V will accept a full charge without issue.

Payment & Security

Payment methods

  • American Express
  • Apple Pay
  • Diners Club
  • Discover
  • Google Pay
  • Mastercard
  • PayPal
  • Shop Pay
  • Visa

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.

Related Products

Schenker XMG U727 Replacement Battery, 15.12V, 5800mAh, Li-ion 1

Engineered for Performance. Built to Last.

Check out our top-rated selection of reliable products built to last. We offer high-quality options that deliver consistent performance for all your needs.

Our Collections