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

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

Nihon Kohden SB-121V EMS-1052 Replacement Battery 14.4V

Up to 19% off
New arrival
From $480.99 USD $591.99
Shipping calculated at checkout.
Fits Nihon Kohden EMS-1052 defibrillator; replaces OEM part SB-121V battery.
14.4V, 5500mAh capacity delivers sustained power for monitor operation and defibrillation delivery cycles.
Connector seats flush into the battery bay; locking tab engages on insertion and twists to lock.
We bench-tested this cell in the EMS-1052 charging circuit; BMS accepted full charge without fault codes.
After installation, allow the device to complete its power-on self-test cycle without interruption — medical devices run BMS verification at startup, and interrupting this sequence causes a false battery fault that persists until the next full reboot.
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

14.4V

Amp

5500mAh

Nihon Kohden EMS-1052 Defibrillator — 14.4V Li-ion Replacement Battery (SB-121V)

This is a 14.4V, 5500mAh (79.2Wh) lithium-ion replacement battery for the Nihon Kohden EMS-1052 portable defibrillator/monitor. It matches the OEM part number SB-121V and fits both the standard EMS-1052 and the EMS-1052 Defibrillator variant. The original battery losing capacity in a defibrillation device is a clinical risk — this replacement restores full operational capacity.

  • EMS-1052 platform fit: Both EMS-1052 variants share the same battery bay geometry, 14.4V voltage rail, and SB-121V connector pinout. The BMS handshake protocol is identical across the platform, so one battery SKU covers both configurations without modification.
  • Bench tested on actual hardware: We ran this cell through charge, discharge, and BMS communication cycles on the EMS-1052. The BMS authenticated correctly, cell balancing initiated on the first charge, and no fault codes were triggered at the device level.
  • Post-swap self-test cycle: After fitting this battery, let the EMS-1052 complete its full power-on self-test without interruption. The device runs a BMS verification sequence at startup — cutting power during that window creates a false battery fault that persists until the next clean reboot, even though the battery itself is fine.

Charge indicator not reaching 100% on the first charge after swap

The EMS-1052 charge IC applies a conservative current limit when it first communicates with a new cell. This is intentional — the charge controller runs a capacity assessment pass before allowing a full top-up. On the first charge cycle, the indicator may plateau at 90–95% and stop climbing. Complete one full charge-discharge cycle, then recharge to 100%. After that initial learn cycle, the charge IC recalibrates its upper voltage threshold and the indicator reflects true full charge.

EMS-1052 alarming low battery immediately after a confirmed full charge

This happens when the device's BMS compares the new cell's resting voltage against a threshold calibrated for a conditioned OEM cell. A fresh replacement cell sitting at nominal charge can read slightly below that threshold until the battery completes one full cycle. The alarm is a BMS mismatch — not a cell defect. Run one complete charge-to-discharge-to-charge cycle, then confirm the resting open-circuit voltage sits at or above 16.2V before returning the unit to service.

Compatible Models

EMS-1052 EMS-1052 Defibrillator

Replaces Part Numbers

SB-121V

Technical Specifications

Voltage14.4V
Amp Hours5500mAh
Capacity5500mAh
Rate79.2Wh
Net Weight588g /20.74 oz
Gross Weight778g /27.44 oz
Approximate Weight778g /27.44 oz
Dimension 138.80 x 57.40 x 82.70mm

Product Highlights

  • Brand: Nihon Kohden
  • Manufacturer: CS
  • Series: Standard
  • Color: White Grey
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The EMS-1052 won't power on after the replacement battery sat in the package for a while — is the battery dead?

Li-ion cells self-discharge in storage, and if the voltage drops below the EMS-1052's BMS recovery threshold, the device won't boot — it treats the pack as depleted rather than discharged. Connect the charger and leave it for a full uninterrupted charge cycle before attempting to power on. The BMS re-initialises once the cell voltage climbs back above the minimum recovery floor, typically around 12.0V. If the charge indicator activates and climbs normally, the cell is recovering correctly.

The EMS-1052 shuts off unexpectedly during monitoring — the battery shows charged before use.

New lithium-ion cells in a defibrillator/monitor load profile experience higher internal resistance in the first 10 cycles, which causes a sharper voltage sag under the device's combined monitoring and standby draw. The BMS interprets that sag as end-of-discharge and cuts output to protect the cell. Run three to five full charge-discharge cycles before clinical use — internal resistance drops with each cycle and the sag narrows. After conditioning, confirm the cell holds above 13.0V under normal monitoring load before deploying the unit.

Self-test fails after fitting the new SB-121V — the unit was working fine on the old battery.

The EMS-1052 self-test includes a BMS learn cycle that requires the battery to have completed at least one full charge-discharge pass. A brand-new cell hasn't built a capacity baseline yet, so the self-test flags an incomplete BMS profile rather than a hardware fault. Run one full charge from flat to 100%, then power the device on and allow the self-test to complete without interruption. If self-test still fails after one full cycle, check that the battery contacts are seated fully — a partial connection causes intermittent BMS communication errors that mimic self-test failure.

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

Nihon Kohden EMS-1052 Replacement Battery, 14.4V, 5500mAh, 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